ethanol từ lignocellulose

8/12/2019 Ethanol T Lignocellulose

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CHNG 4 :ETHANOL TLIGNOCELLULOSE

4.1 Lignocellulose v hng s dng:

4.1.1 Lignocellulose

Cc cht liu cu trc ca thc vt hnh thnh thnh tbo, l, thn chyuc cu to tcc biobased l cc loi phn tha hc , thng c phn thnh ccnhm sau : cellulose,hemicellulose v lignin. Nhng cht sinh hc c bn ny thngc gi chung l lignocellulose, lignocellulose biomass , hoc cc vt liulignocellulose.Nh thhin trong hnh 4.1 y v cng trong Chng 3, mt tbothc vt thng thng c kt cu ging nh mt vt liu composite trong sixenlulo cng c gn trong mt mng lin kt ngang ca lignin v hemicellulose c linkt vi cc si cellulose.

Thng thng khi lng kh ca thnh tbo thng thng gm c khong 35-50% cellulose, hemicellulose 20-35%, v 10-25% lignin [1]. Nhng loi khc ccellulose thng chim 40-50% gsinh khi, trong khi lignin v hemicellulose michim khong 20-30%. Mc d lignin chc 20-30% trong nhng loi lignocellulose

biomass thng thng, nhng n cung cp 40-50% gi trtng nhit hoc tng snnglng c sn biomass, do nhit trcao hn (CV) so vi cellulose v hemicellulose. iuny gii thch ti sao chuyn ha hoc li ch ca vic sdng lignin l rt quan trngtrong vic sdng nhin liu / nng lng cc ngun ti nguyn lignocellulose.

Cu trc biomass lignocellulose cn cha mt lot cc cht sinh hc c trngtrong cht nn, chng bao gm extractives (nh nha, phenolics, v cht ha hc khc)v cht khong (canxi, magi, kali,v nhng cht khc) m scn li trong tro biomasskhi c t. Cc khong vi lng v cc thnh phn quan trng trong vt liulignocellulose c gi trthnh phn khc nhau gia cc loi khc nhau, gia cc bphnkhc nhau trong mt cy no , v cn ty thuc vo cc iu kin pht trin bao gmcc tnh ca t [2]. Ngoi vic c thnh hng sc khe v mi trng , khongcht c ththhin tc ng mnh mtrn cc quy trnh xl ha hc giai on tip

theo, bao gm cc vn lin quan n nhit ng ca xc tc chuyn ha cc cht trunggian ca lignocellulose.


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Cellulose l mt phn tpolymer ln gm hng trm hoc hng ngn ccmonomer l cc phn t ng (glucose) , v vphng din ny n c thc coi lmt polysaccharide. Cc mi lin kt phn tca cellulose dng mch thng rt cng,tnh n nh cao, v khnng chng n mn ha hc. Do cu trc polymer thng ca n,cellulose c nhng c tnh ca tinh th[3], v d, cellulose c thphn no ha tan trongmt dung mi thch hp. Tuy nhin, cc phn tcellulose dng tinh thca n clin kt rt cht chm ngay ccc phn tnhnh nc khng c thddng xmnhp c vo cu trc. Mt cch logic, n scn kh khn hnna cho cc enzyme lnthm hoc khuch tn vo cc cu trc cellulose. Ngoi ra, Cellulose tn ti trong mtmng polyme khc, chyu l hemicellulose v lignin, nh minh ha trong hnh 4.1.

Mt thnh phn khc, hemicellulose bao gm chui phn tng rt ngn vnhiu nhnh N cha cng 5C (thng D-xylose v L-arabinose) , ng su-carbon (nh D-galactose D-glucose v D-mannose) v axit uronic. V d, galactan, ctm thy trong hemicellulose, l mt polymer ca ng galactose, c khnng ha tantrong nc vi tan 68,3 g cho mi 100 gram nc nhit phng. Axit uronic l

mt dng ng acid vi mt gc cacbonyl v mt nhm chc carboxylic.Hemicellulose c dng v nh hnh do cu trc phn tphn nhnh cao ca n [3] vkh ddng thy phn thnh nhng phn tng n gin cu thnh nn n, cng nm Cv ng 6C. Khi thy phn, hemicellulose tgcng thot ra cc sn

phm c hm lng ng cao di dng xylose (mt loi ng nm C), trong khihemicellulose cha trong gmm thng cha nhiu ng 6 cacbon nhiu hn.Mc d


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chai ng 5C v ng su carbon, minh ha trong Hnh 4.2, u l ng ln menn gin nhngc skhc bit trong qu trnh ln men ha hc v cc qu trnh ctrng vi cc loi men v enzymes cth.

Con ngi c nhiu kinh nghim hnv thnh cng trong qu trnh ln mencc loi ng su-carbon (hexoses)nhiu hnso vi ng nm carbon (pentoseshocxyloses), iu c minh chng bng mt lch slu di ca vic sn xut ungc cn trn ton thgii. Tuyn bny vn cn gi tri vi vic sn xut ethanol nhin

liu tln men . Nhiu nm trc y,ngi ta tin rng xylose khng thc ln menbng nm men, nhng trong nhng nm gn y, mt snm men c tm thy ckhnng ln men xylose thnh ethanol [4, 5]. kthut di truyn xylose ca qu trnh lnmen trong nm men cng c thc hin vi kt quthnh cng [6].

Lignin l mt polymer thm phc tp v c lin kt ngang l lin kt ha trlinkt vi hemicellulose, nh thhin trong hnh 4.1. Lignin gp phn n nh thnh t


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bo trng thnh. Lignin mang li nhiu nng lng hncellulose khi bt chy donhit trcao hn. Lignin l mt i phn tc trng lng phn tc trng ln hn10.000. Do cu trc lin kt ngang ca n, lignin thng skh khn hn xl,chit thy phn, hoc phn ng so vi xenlulo hoc hemicellulose. V vy, phn tch,

phn hy sinh hc ca cu trc lin kt ngang l bc u tin sn xut nhin liusinh hc tnguyn liu cellulose. Cn thit ni, hiu quchuyn i ca lignin sdnn mt gia tng ng khiu sut nhin liu cng nh nng cao trin vng kinh tvivic sdng lignocellulos.

4.1.2 Phn tch cenllulozo, chuyn ha v hng sdngCc nc ang pht trin c nn kinh tyu km v khng c shtng cng nghip btn thng nghim trng bi cuc khng hong nng lng. Khai thc trit timnng ca nhin liu ha thch da trn ngun c sn v cc ngun ti nguyn ti to thaythkhc, cn ngun vn ln ng k, iu m cc nc ang pht trin c ththiu , l

bt buc. Do xu hng c thay i theo hng quy m nhhoc sdng tinguyn nng lng ni a ho . Mt lnh vc c tim nng y ha hn cc nc ang

pht trin c tht c thnh cng tng i nhanh chng l bsung ngun cung cpnhin liu ha thch ca hvi nhin liu ti to thay thc ngun gc tthc phm vcy trng nng nghip nh ma, sn, ng, v la min. La chn ny cng l khthi chocc nn kinh tpht trin.

Du mc xem l ngun nhin liu chnh cho giao thng vn ti , ethanol thu ht c rt nhiu sch nh mt ngun nhin liu lng thay thcho xng hoc

pha trn xng gim tiu th xng thng thng. Chng trnh sn xut ethanol nhinliu thay th c theo ui nghim tc nht bi Brazil v Hoa K. Brazil, tt ccc xe u ang chy gasohol ( mt hn hp 22 % vol ethanol vi xng , hoc E22 , bt

buc vo nm 1993 , vi tlpha trn 25% , hoc E25 , bt buc tnm 2007 ) hocethanol tinh khit ( E100 ) . Brazil, Chng trnh Quc gia vAlcohol(NationalProgram of Alcohol) , PROALCOOL , bt u vo Thng 11 nm 1975 , c ra p ng vi cuc khng hong nng lng u tin vo nm 1973. chng trnhny thts c hiu qulm thay i lng tiu thnng lng c nhn quc gia ny. Vo nm1998, nhng chic xe ethanol htrtiu thkhong 2 tgallon ethanol mi nm v

khong 1,4 tgallon ethanol bsung c sdng sn xut xng pha cn ( E22 ,tc l 22 vol % ethanol v 78 % vol xng ) cho xe t khc [7] . Vo thng Ba nm2010, mt skin quan trng l 10 triu flex - nhin liu xe ethanol c sn xut tiBrazil. Chng trnh Brazil chng minh sn xut ethanol thnh cng quy m ln tma v vic sdng ethanol lm nhin liu ng c bn vng. Trong nm 2010,Brazilsn xut khong 6920000000 gallon [8] ethanol , trong khi Hoa Ksn xut hn 13,2 t


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gallon ; sn xut nm 2010 ca Ml hn hai ln so vi nm 2007 (6,5 tgallon ) vkhong tm ln ln hn so vi nm 2000 (1,62 tgallon ) .Nh chng minh trn ,ethanol c c coi l cht ha hc pht trin nhanh nht ti Hoa Ktrong thp kqua.Hai quc gia ny mt mnh chu trch nhim cho khong 90% sn xut ethanol cng

nghip trong nm 2010 ca thgii.Lin quan n nng kh quyn cc kh nh knh (GHGs) , The National

Research Cuoncil (NRC) theo yu cu ca Quc hi v vi sti trca BNng lngM, nhn mnh scn thit ca vic nghin cu nhiu hn v pht trin ngun nnglng ti to , cc phng php ci thin vic sdng nhin liu ha thch , bo tn nnglng v cc cng nghtit kim nng lng . Theo o lut Chnh sch Nng lng (EPAct ) nm 1992 c thng qua Quc hi M nhm gim sphthuc ca qucgia vo vic nhp khu du kh bng cch yu cu thit kc c xe nhin liu thaythc khnnghot ng trn nhin liu nonpetroleum . Nhin liu thay thcho xngdu vn hnh xe , theo quy nh ca o lut chnh sch nng lng , bao gm ethanol,kh thin nhin, propan, hydro, nhin liu sinh hc , in, methanol, v nhin liu p -series. nhin liu P -Series l mt hca nhin liu ti to c ththay thcho xng . olut Chnh sch Nng lng nm 2005 thay i chnh sch nng lng ca Mbngcch cung cp u i vthuv bo lnh vn vay cho sn xut cc loi nng lng khc,trong bao gm vic ct gim thui vi xe c ng c v nhin liu thay thtrongbao gm ethanol sinh hc [9] .

Hoa Kkhng bthiu cc ngun nng lng (n c nhiu than v phin du d

tr), nhng Hoa K chcn cht lng thng thng cho nhin liu vn ti. Thtrngcho nhin liu vn ti c thng trbi cc loi nhin liu tdu mv xu hngny dkin stip tc trong mt thi gian ti. Rt ng cc nh nghin cu trn thgii nghin cu vsn xut nhin liu sinh hc lng tbiomass v than [10]. H tmthy vi sinh vtc thsn xut ethanol tbiomass, chuyn i kh tnhin vo ethanol,v chuyn i kh tng hp c ngun gc tqu trnh kh ha than thnh nhin liung.Cc vi sinh vt c xc nh l to ra ngun nng lng hiu quv y ha hncho sn xut cng nghip. Qu trnh hot ng ca vi sinh vt nhit bnh thng vdi p sut bnh thng v cung cp li thng kso vi qu trnh ha hc,nh ha

lng than trc tip v tng hp tphn ng Fischer-Tropsch, hot ng trong iu kinkhc nghit sn xut nhin liu lng tthan .

Cc nh nghin cu tp trung vo sdng lignin nh mt ngun nng lng ti to thay th nhin liu lng truyn thng. Lignin c sn xut vi slng ln Hoa Knh l cc sn phm ca ngnh cng nghip giy v bt giy. Kt qul, gi mt ssn

phm lignin, nh lignosulfonates hoc lignin sunfonat, l tng i thp. Lignosulfonates


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c sdng chyu nh cht ho do trong vic to b tng v cng c sdngtrong sn xut thch cao. sn lng ton cu lignin cho cc ng dng cng nghip khcnhau c c tnh l kh cao,mc d cha c sliu thng k ng tin cy . TrungQuc, vic sn xut lignin tng t32 triu tn trong nm 2006 ln 45.000.000 tn

trong nm 2010, vi tc tng trng tng i nhanh.

4.2 Chuyn ha Lignocellulose

4.2.1 Ethanol

4.2.1.1 Ethanol Ha cht v nhin liu

Ethanol, C2H5OH, l mt trong nhng hp cht hu c cha oxy quan trng nht. Vinhng tnh cht ha l c bit, ethanol c rt nhiu ng dng nh lm dung mi, nhinliu, cht st trng, thc ung v cht chng ng; ngoi ra, khnng linh hot nhmt cht trung gian gia cc ha cht v sn phm ha du cng l mt vai tr quantrng ca n. Ethanol l mt trong nhng ha cht c sdng nhiu nht trong cngnghip v sn phm tiu dng. Hai trong cc ng dng quan trng ca ethanol l ngvai tr nh mt dung mi v mt cht trung gian trong qu trnh sn xut cc ha cht.Ethanol l dung mi phbin thhai, chsau nc. y l nguyn liu th tt yu trongsn xut nha, sn mi, xi m, cht ha do, nc hoa v m phm. Tnh cht vt l vha hc ca ethanol phthuc chyu vo nhm hydroxyl, vi vai tr nhmt in ccv c bit l tham gia hnh thnh lin kt hydro lin phn t. trng thi lng, lin kthydro c hnh thnh bng lc hp dn gia nguyn thydro trong nhm OH ca phntny vi mt nguyn toxy trong nhm OH ca mt phn tkhc. Stng tc nychc pha lng, cn pha hi, phn tru tn ti n l.

Mt tnh cht quan trng khc ca ethanol khi ng dng vo lnh vc nhin liu, l hru-nc to im ng ph nng 95.63 wt% ethanol v 4.37 wt% nc,hn hp ny si 78.15 oC, thp hn so vi nhit si bnh thng ca ru (78.4oC).V vy, khi chng ct n thun, khng thnng nng ethanol cao hn nng ny.Ethanol dng trong nhin liu thng c sn xut bng vic kt hp chng ct v hp

phhoc hp thvt qua nng im ng ph.

4.2.1.2 Sn xut ethanol cng nghip

Cn cng nghip c sn xut tethylene, sn phm phca cc phn ng, hoc tqutrnh ln men ng, tinh bt, xenlulose. C hai qu trnh chyu tng hp ethanol tethylene, hydrat ha trc tip v gin tip. Hydrat ha l phn ng ta nhit v thunnghch, do , chuyn ha ti a bgii hn bi cn bng ha hc.


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Ch c khong 5% ethylene c chuyn ha thnh ethanol trn mi dng phn ng.

Bng phng php tch ethanol ra khi hn hp cn bng v hon lu ethylene chaphn ng, c th t n chuyn ha 95%. iu kin phn ng in hnh nht l300oC, 6-7 Mpa, sdng xc tc acid phosphoric trn cht mang silica gel hoc vt liudiatomaceous. Qu trnh ny c ng dng ln u tin trn quy m cng nghip vonm 1947 bi cng ty Shell Oil Company.

Ngoi qu trnh hydrat ha trc tip, cc qu trnh khc nh ln men, sulphuric acid,cng c xut nhng khng c ng dng thnh cng trong quy m cng nghip.

4.2.1.3 Qu trnh ln men ru

L mt trong nhng qu trnh ha hc lu i nht c ng dng bi loi ngi, lnmen c sdng sn xut nhiu loi sn phm v ha cht hu dng. Trong nhngnm gn y, nhiu loi sn phm tng c sn xut bng qu trnh ln men, nay ctng hp tngun nguyn liu du kh, thng c gi thnh thp hn v chn lc caohn. Tuy nhin, cc ngun nguyn liu sinh hc ang c u tin hn cc ngunnguyn liu ha thch, cng nh ch trng n cc qu trnh thn thin vi mi trng,theo hng o, nhiu qu trnh lin quan n cc ha cht c hi ang c chuynsang phng php x l sinh hc, in hnh l qu trnh ln men. Do , tng lai cacng nghip ln men ph thuc nhiu vo vic p dng cc loi xc tc enzym c hiuquv hot tnh cao cho cc qu trnh tng hp phc tp, cng nh vt qua cc vn vcht lng v tnh sn c ca vt liu.

Ethanol c th thu c d dng tqu trnh ln men cc nguyn liu c cha nghoc tin t ca ng. Cc ngun vt liu th c s dng sn xut cn bng

phng php ln men c thphn thnh cc loi: ng, tinh bt v vt liu cellulose.ng c th chuyn ha trc tip mt cch n gin thnh ethanol. Cn tinh bt cnc thy phn thnh ng bng cc loi enzyme trc khi ln men. Tng t, cellulsecng phi c chuyn ha thnh ng trc, thng thng di tc dng ca mt s

loi acid v c (v d: acid sulfuric, acid chlohydric, acid nitric). Khi cc loi ng nc hnh thnh, enzyme t cc loi men s c s dng ln men chng thnhethanol.

4.2.1.4 Qu trnh ln men ng

Dng ng c s dng ph bin cho qu trnh ln men sn ru l blackstrapmolasses, c cha khong 30-40% sucrose, 15-20% ng chuyn v nh glucose v


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fructose, v 28-35% cht rn khng ng. Cc phng php ln men trc tip nc ma,nc p c ci ng, r ng, tri cy ti v kh, c ra nhng khng

phng php no t hiu qukinh t cao. Da trn quan im sn xut ethanol cngnghip, cc nguyn liu giu sacrose nh nc p ma v cci ng c kh nhiu u

im, c bit l sdi do v khnng ti sinh ca chng. Gng, phn bkhng thkt tinh cn li sau qu trnh tinh ch sucrose, cn c nhiu u im hn: l ngunnguyn liu th tng i rtin, c sn v c sdng trong sn xut ethanol cngnghip. Gng c sdng sn xut mt snc ung c ln men nh biaen v cru rum. Ti Brazil, bioethanol c sdng da trn nguyn liu l ma vp dng nhng cng nghu tin c sdng da trn ngun sucrose c trong ma.Tng sn lng v m rng phm vi l 2 vn c bn c Goldemberg andGuardabassi tho lun nhm tng cng tim nng ca vic sn xut ethanol t ma Brazil.

Park v Baratti nghin cu ng hc ca qu trnh ln men theo m, p dng cho mtgca cci ng, bng mt loi vi khun roi c tn l zymomonos mibilis, c tmthy trong nha ca cc loi cy giu cht ng. Z.mobilis phn gii ng thnh

pyruvat bng qu trnh EntnerDoudoroff. Pyruvate sau c ln men sinh ra ru vCO2. Loi vi khun ny c nhiu tnh cht kh th vv li ch, c thcnh tranh vi ccloi men bia truyn thng, thm ch cn vt bc so mt smt; in hnh l n cho ranng sut ethanol cao hn, khnng hp thu ng cao hn, v hn chsn xut cc sinhkhi.

Tuy nhin, khi c cy trn gng, Z. mobilis nhn chung pht trin km hn v chonng sut ethanol thp hn so vi khi c cy trn glucose. Sn lng ethanol thpc gii thch l do shnh thnh cc sn phm phnh levan v sorbitol. Cc thnh

phn khc trong gng nh mui hu c, nitrate, hoc cc hp cht thm cng c thcn trspht trin ca loi vi khun ny. Do , lm hn chvic to ra cc loi ngn nh glucose, fructose v sucrose. Park v Baratti chra rng sn lng v nng ethanol l khng cho cc qu trnh cng nghip.

Trong mt cuc nghin cu bi Kalnenieks, vi nng (20500 M), KCN lm ngn

cn tc h hp hiu kh nhng li kch thch ng spht trin ca Z.mobilis. Ccnh khoa hc, in hnh l Cazetta, cng nghin cu vnh hng ca nhit vnng ng i vi vic sn xut ethanol bng Z. mobilis. Hsdng cc m hnh thnghim c m phng nh cc nh my thc kho st cc iu kin phn ng khcnhau, bao gm nhit , nng rng, v thi gian tin hnh. Hkt lun rng iukin ti u sn xut ethanol l 200 g/L rng, 30C, trong vng 48 gi, thu c55.8 g ethanol/L.


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Cc loi men ci saccharomyces genus c sdng ch yu trong cng nghip lnmen ru. in hnh l Saccharomyces cerevisiae, loi men c sdng rng ri trongcc qu trnh bia, ru. Tuy nhin, S. cerevisiae khng th ln men D-xylose, dngng phbin thhai tcc loi vt liu cellulose. Mt loi men ci c khnng t

nhin ln men D-xylose thnh ethanol l Pichia stipitis, tuy nhin, loi ny khng ckh nng chu ng ethanol v cc cht c ch nh l loi men truyn thng,Saccharomyces cerevisiae. V vy, ng dng ca n trong cng nghip cn rt hn ch. c nhiu n lc nhm sn sinh ra dng men S. cerevisiae c khnng ln men D-xylose bng cch ci tin vmt gen. Cc nh khoa hc v ang nghin cu nhm lnmen xylose vi nng sut v sn lng cao bng nhng loi Z.mobilis khc nhau c khnng sdng ng C5 nh mt ngun cacbon. Nhng tin bvi kt quy ha hn c trnh by trong bo co.

Bng cch can thip vo cu trc gen, Tao bin i ging Escherichia coli B, c khnng sn sinh acid hu c, thnh ging E. coli strain KO11, c khnng to ra ethanol.Loi KO11 ny c th sn sinh ra 0.50 g ethanol/g xylose t dung dch 10% xylose 35C v pH 6.5. y l mt v din hnh khnng bin i cc loi vi khun. Bngvic kt hp cc k thut bin i chuyn ha h thng sinh hc, c hai phng phpc ra nhm pht trin khnng ca cc dng vi khun:

1. Ti thp cc chth: cy cc loi gen l tng vo cc chthc tcht csdng trong cng nghip, vi cc cng cti thp.

2. Tip cn cc ch th tnhin: vn dng cc loi vi khun mi vi cc khnng

nh mong mun nhm pht trin cc c im cn thit c th ng dng trongcng nghip v loi bnhng yu tkhng mong mun.

Nghin cu vloi men ci c thln men xylose thnh ethanol c tin hnh tchcc, c th l nhn mnh vo vic bin i gen ca Saccharomyces cerevisiae. S.cerevisiae c xem l mt vi sinh vt an ton, ng vai tr truyn thng v ch yutrong cng nghip bioethanol hin i. Saccharomyces cerevisiae c mt s u im,

bao gm nng sut ethanol cao cng nh khnng chu ng ethanol v cc cht c ch.Khng may thay, loi men ci ny khng c khnng ln men xylose. Mt schnh sch

da trn bin i gen v vi sinh hin i c p dng nhm cung cp cho loi menny khnng sn xut hiu quethanol txylose. Mt schin lc mi bao gm: (a)gii thiu khnng chuyn ha s bv vn chuyn xylose, (b) bin i cn bng oxyha khni bo, v (c) con ng overexpression of xylulokinase v pentose phosphate.Mt trong nhng nghin cu tin phong l vic pht trin loi men Saccharomyces c bin i v gen, c th ln men ng thi glucose v xyle thnh ethanol biSedlak cng cc cng s. Loi men Saccharomyces cerevisiae ti thp cng khnng


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chuyn ha xylose ca hc xem l hiu qunht; tuy nhin, hin ti chng vn trahiu quhn i vi glucose thay v xylose.

Theo kt qunghin cu ca h, glucose c tiu thnhanh chng khng n10h, trong khi xylose li c chuyn ha chm hn v khng hon ton. Thc t, xylose

vn khng c tiu thhon ton thm ch sau 30 gi. Vmt l thuyt, xylose l raphi c chuyn ha ng thi vi hiu sut v tc tng tnh glucose; tuy nhin,vic bsung khnng ln men ng thi glucose v xylose vn chdng li nghincu. Hn na, hquan st c rng, mc d ethanol l sn phm chnh thu c, vncn tn ti mt slng nhcc sn phm phchuyn ha ca glycerol v xylitol. Haivn nu trn, cng vi vic tng hiu sut v ti u ha vic ln men xylose, cng nhiu chnh cc sn phm ph, l nhng ni dung cn c nghin cu su hn.

4.2.2 Ngun nguyn liu ln men ng

4.2.2.1 Tinh bt

La go thng l ngun nguyn liu rtin sn xut ethanol nhiu nc trnthgii v n c thd trddng. Ngoi ra, cc sn phm ph t la go c thsdng lm ngun thc n giu protein cho gia sc. Qu trnh ln men tinh bt tla govn d phc tp, bao gm nhiu bc hn so vi ng bi v tinh bt buc phi cchuyn ha thnh ng ri sau l ethanol. Phng trnh n gin cho schuyn hatinh bt thnh ethanol nh sau:


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Theo s 4.3, qu trnh sn xut ru go bao gm, chng tch dung dch ng tnguyn liu, ln men ng thnh ethanol, v tch ethanol tnc thng qua chng ct.

Mt trong nhng bt li khi sdng la go l sbin ng vgi c. Mt sch trch cho rng vic sn xut ru t ng cc l nguyn nhn gy ra smu thunnng lng v lng thc, cng nh s tng ln v gi c lng thc hin nay, tuynhin mt sngi phn i mnh mt tng ny vi nhng thng k v nguyn nhnmt cch logic. Ethanol pha xng gip tng chsoctan cng nh khnng chy schhn. Ti M, ethanol hin l ngn nguyn liu c oxy phbin nht, c cp ntrong chng 3.

4.2.2.2 Vt liu cellulosic

Cellulose tg, b thc vt, v rc thi tbt giy cn phi c chuyn hathnh ng trc khi ln men. Mt lng ln rc thi cacbonhydrat, c cha ccellulose c thi ra hng nm trn ton thgii. Ethanol tcellulose c xem l mt

phng n gim hin tng kh thi nh knh, v hn 90% nhin liu truyn thng datrn sn phm du m. Ngoi ra, ethanol tcellulose khng b phn nh lin quan nvn nng lng v lng thc. Nhng phng n mi nhm gim gi thnh sn xutru cellulose bao gm pht trin nhng phng n gia cng s bhiu qu, thay thqu


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trnh thy phn vi acid bng cc loi enzyme thch hp, thng mi ha cc enzyme tt,la chn cc qu trnh thy phn v ln men hiu qubng enzyme vi cng C6

4.3 Bi cnh lch sca cng nghln men Alcohol

Mc d t c quan tm trc , ethanol cellulosic c mt lch skh phongph. mt trong nhng nlc u tin ghi nhn trong lnh vc thng mi ha qu trnhsn xut ethanol cellulosic c thc hin c vo u nm 1898. Qu trnh nyc da trn sdng axit long thy phn cellulose thnh glucose v tip theo lnmen glucose sn xut ethanol. Bo co sn lng l 7,6 lt ethanol trn mi 100 kgcht thi g, tng ng vi 18 lt mi tn. Nh mt khi u, vic chuyn i chtthi gthnh ethanol kh ng ghi nhn, qu trnh ny c tng cng hn na c mang li khong 50 gallon ethanol trn mi tn biomass. Hoa Kqu trnhny c tng cng hn na trong thi gian Thchin thnht bng cch p dng mt

giai on duy nht l qu trnh pha long thy phn axit sulfuric , do tng sn lngethanol cho mi biomass u vo thp hn so vi quy trnh gc c khong 50%.

Nhng thng lng ca qu trnh ny l cao hn nhiu. Quy trnh ny Mdin ra ngnngi, do sst gim ng kvsn lng gtrong thi khu chin . Tuy nhin, qutrnh ny c a vo hot ng thng mi mt ln na trong Thchin II snxut butadien bng cch chuyn i ethanol vi mc ch sn xut cao su tng hp. Mcd qu trnh t c sn lng ethanol 50 lt / tn kh cellulose g,tuy nhin sosnh nng sut vi li nhun dn n quy trnh ny dng li sau chin tranh. thm chmc d sn xut thng mi c dng li, hot ng nghin cu vcellulose ethanolvn tip tc trn ton thgii, v c tng cng hn na do hu quca cc cuckhng hong du m, mc tiu thnhin liu sinh hc ang bng nv t c nhiutin bnhanh chng trong cng nghsinh hc.Nm 1978, cc nh nghin cu Gulf Oil [33 ] thit kmt nh my quy m thng mi sn xut 95 106lt ethanol mi nm

bng cch thy phn v ln men bng enzyme ng thi cellulose bng con ng nc hnh thnh ,do khc phc vn vsn phm. Qu trnh ny bao gm mt giaion tin xl bng cch nghin v gia nhit sn phm tip theo thy phn vi mt loivi khun gy t bin , cng l mt loi c bit c pht trin cho mc ch ny .Chng t bin ny ging vi Trichoderma viride c thx l nhiu hn gp 15 lnso vi cc chng tnhin.Thy phn v ln men ng thi lm gim yu cu thi giancho bc thy phn ring bit, do lm gim chi ph v tng nng sut .Ngoi ra , qutrnh ny khng sdng axit do skhng lm tng chi ph cho cc thit bi km.Hiu sut sn phm ng thu c tcellulose khong 80 % theo l thuyt c ththchin c , nhng mt slng nhhemicellulose trong mn ca khng c chuyn


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ha . Thc tny cho thy mt nhu cu cho mt giai on tin xl hiu quhn cthtch c hemicellulose.

Nhnhng tin btrong cng nghenzyme c pht hin, qu trnh thy phnbng axit tng bc c thay thbng mt qu trnh thy phn enzyme hiu quhn.

t c hiu qucho qu trnh thy phn bng enzyme , cc loi ha cht hoc mtgiai on tin xl sinh hc cho cc nguyn liu xenlulo trthnh cn thit cho

prehydrolyze hemicelluloses nhm tch chng ra khi lignin.Cc nh nghin cu caForest Product Laboratory ca U.S Forest Service(USFS) v i hc Wisconsin-Madison pht trin giai on tin xl bng sulfite vt qua ro cn ca lignocellulose(SPORL) cho qu trnh ng ha lignocellulose bng enzyme c din ra mt cchthun li [34].

Cellulase l mt lp cc enzyme xc tc cho qu trnh cellulolysis, nhm ph v

chui cellulose thnh cc phn tglucose. Trong nhng nm gn y, cc cng ty chuynv enzyme v cc ngnh cng nghip thuc lnh vc cng nghsinh hc gp phnng kto nn cng nght ph trong cng nghsn xut ethanol cellulosic thng qua

pht trin enzyme cellulase cho hiu qucao cng nh sn xut hng lot cc enzyme cli thkinh t. Research,development and demonstration (RD & D) trong enzymecellulase c thc hin bi nhiu cng ty quc tnh Novozymes, Genencor,Iogen,SunOpta, Verenium, Dyadic International, v cc phng th nghim quc gia nh

National Rnwwable Energy Laboratory (NREL). Ethanol cellulosic ginh c snghmnh mv nhn c shtrng kca Tng thng MGeorge W. Bush trong

Nh nc Lin bang. Trong bi pht biu vo ngy 31 thng 2006, xut mrng vicsdng cc ethanol cellulosic Trong bi pht biu ny, Tng thng Bush vch ra chi titAmerican Competitiveness Initiative(AEI 2006) gip khc phc sphthuc ca Mvo cc ngun nng lng nc ngoi v nng cao nng lc cnh tranh ca M(ACI2006) tng cng u t R & D v tng cng gio dc Cc chng trnh chun (RFS)vnhin liu ti to c ban hnh theo o Lut Chnh sch nng lng nm 2005(EPAct 2005) v thnh lp khi phtrch nhim vvcc vn nhin liu ti to tiHoa Kln u tin. Chng trnh chun RFSban u c gi l RFS1. RFS1 yu cu7,5tgallon nhin liu ti to c pha trn vo xng vo nm 2012. Yu cu vmt thi

gian v sn lng nhin liu ti to sau c sa i v mrng.

o lut c lp v an ninh vnng lng ( EISA ) thng qua nm 2007 thit lpmc tiu lu di cho vic sn xut nng lng ti to nhin liu thng qua cc nhin liuti to thhai theo Tiu chun ( RFS2 ) . Chng trnhRFS2 mrng khi cho php snxut ethanol tmt lng ng ln u tin v thi gian thc hin RFS ban u , theo EPA ca Hoa Kchu trch nhim thc hin cc quy nh m bo rng khi lng


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nhin liu sinh hc cho ngnh giao thng vn ti c sn xut tng ln . EPA ca HoaKban hnh quy nh cui cng cho RFS2 mrng vo thng Hai nm 2010, thng qu ,n quy nh mt cch php l vic thit lp khi lng cthhng nm , cho tng skhi lng nhin liu ti to , ttt ccc ngun nhin liu ti to [ 35 ] . Nh l mt

nhim vc khnng nh hng n tng lai lu di ca sn xut ethanol tng,nhim vRFS2 chra rng t nc cn thit phi pha trn 36 tgallon nhin liu tito vo lnh vc nhin liu giao thng vn ti nm 2022 , trong 16 tgallon dkin si tqu trnh sn xut khng da vo lng thc (ng) to ra ethanol. EPA Hoa Kcho rng khi thc hin RFS2 lm gim ng klng kh nh knh m Mthi ra do vicvn chuyn. Vo thng Hai nm 2010, Nh Trng di slnh o ca Tng thngBarack Obama ban hnh " Growing Americas Fuel " l mt ltrnh ton din nhin liu tin tin c trin khai [ 36 ].

Nm 2004, cc nh nghin cu ti National Renewable Energy Laboratory phihp vi hai nh cng nghip sn xut enzyme ln ( Genencor International v

Novozymes Biotech ) t c thnh tu gim ng kchi ph sn xut enzymecellulase, l mt trong nhng trngi ln trong thng mi ha ethanol cellulosic .Cellulase thuc mt nhm enzym c gi l hydrolases glycosyl , m cleave (Hydrolyze )lin kt ha trvi mt carbohydrate ca phn tkhc . Cc cng nghmilin quan n mt loi hn hp ca ba loi cellulase : endoglucanases , exoglucanases,v beta- glucosidases . Cc enzym htrcng lm vic vi nhau tn cng chuicellulose , ko chng ra khi cu trc tinh th,ph cc phn tcellobiose ( hai phn tglucose lin kt vi nhau ) , tch chng thnh cc phn tng ring l, v lm chochng sn sng cho vic tip tc xl enzym. Cng vic mang tnh t ph ny lmgim n 20 ln chi ph v ginh c gii thng R & D 100 cho NREL v cc cngtc vin [ 37 ] .

iu ny chc chn l mt ct mc thnh tu trong spht trin ca cng nghsn xut ethanol cellulosic , tuy nhin, Yu cu gim chi ph hn na trong vic sn xutenzyme cellulase , cc con ng mi cn phi c pht trin nng cao hiu quca enzym, pht trin enzyme c khnng chu nhit cao hn v ci thin hot ngmong mun cth, kt hp tt hn giaenzym vi cc polyme to thnh tbo thc vt

cn phi t c, mt lng enzyme rn vi hiu quc nng cao cn c phttrin v nhiu hn na. Hi tho BNng lng ca MBo co tm tt mt cch chitit v khoa hc, nghin cu xc nh nhu cu trong khu vc nhin liu sinh hc BiofuelsJoint Roadmap [26].

Trong nhng nm gn y, nhnhng tin bln trong lnh vc kthut ditruyn v vi sinh hc tin tin c p dng trong vic pht trin qu trnh to hthng


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vi khun c khnng hp tc hiu ququ trnh ln men cho C5 v ng C6 v ckhnng c chskhng thuc i vi cc qu trnh bin i.

Mt hng nghin cu khc sn xut ethanol cellulosis l thng qua sdngxc tc chuyn i cc sn phm kh thng qua cc qu trnh bin i ha hc m khng

cn sdng enzymes. Chc chn c mt ng cn bng gia sdng phng php hahc v enzym bao gm chiu sut, chn lc sn phm,tc phn ng,chi ph gic, mc tiu tn nng lng nguyn liu linh hot v hn na. Mt trong nhng nlcthc hin sdng xc tc cho cc qu trnh ha hc tbiomass c thc hin quym thng mi nm 2007 do Range Fuel thc hin bng ca nm 2011 m khngt c mc tiu ban u.

4.4 Ngun nguyn liu Lignocellulose nng nghip

Cho n nay, mt l do m thgii phthuc qu nhiu vo cc ngun kh thinv du mthu c nng lng v sn xut hu ht cc vt liu hu c l cc chtkh v lng tng i d s dng. Cc ngun vt liu rn nh g gp nhiu kh khntrong vic thu hoch, vn chuyn, v chbin thnh cc sn phm mong mun dng chocung cp nng lng. Do , cc ngun nguyn liu rn vn cn thiu nhiu cc qu trnhchbin lin tc v gii quyt cc kh khn trong vic sdng.

Ni mt cch n gin, lignocellulose nng nghip c gi thnh khng cao v cthti to v chng c thc to ra bng qu trnh quang hp vi ngun nng lng

mt tri. Ngoi ra, s lng cc loi nguyn liu sinh hc vn c chuyn ha thnhnhin liu, ha cht, v cc vt liu khc l khng gii hn. Vic s dng cc ngunbiomass nhiu hn cng c thgip ci thin cc vn lin quan n cht thi rn. Nm2009, 243 triu tn rc thi rn th(MSWs) c thi ra nc M, tng ng vi4.3 pounds rc thi theo u ngi mi ngy. i vi loi cht thi ny, 28.2% l giy v

ba cng, 13.7% l rc thi tcc phn xng, 6.5% l g, v 14.1% l vn thc n.Trong , 50% tng src thi rn thl cellulose v c thbin i thnh cc chtha hc v nhin liu hu ch.

Mc d lignocellulose khng mc tin, nhng n i hi cn phi c bin i

thnh cc loi ng c thln men. Hn thna, nh trong Figure 4.4, lignocelluse ccu trc ha hc phc tp vi 3 thnh phn chnh, v mi thnh phn cn c bini ring vic c thsdng tt nht gn lin vi cc qu trnh sinh hc. 3 thnh phnchnh ca lignocellulose l tinh thcellulose, hemicellulose, v lignin.


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Mt s tng quan vvic chuyn ha lignocellulose thnh ethanol c m ttrong Figure 4.5. Lignocellulose c xl phn tch xylose v lignin ra khi tinh thcellulose. y l bc rt quan trng, v hiu sut ca qu trnh xl nh hng n hiusut ca cc bc sau . Xylose tch ra c thc ln men thnh ethanol, trong khi lignin c thc chbin tip sn xut cc ngun nhin liu lng v ha cht c gitr. Tinh thcellulose, chim nhiu nht (khong 50%) v hu ch nht, c gili di

dng rn sau qu trnh xl v c a n cc qu trnh thy phn c enzyme nhm bgy cellulose thnh glucose. Cc enzyme, nh l xc tc sinh hc, c tnh c hiu cao,do qu trnh thy phn cellulose thnh ng khng lm b gy tip cc phn tng. Cc qu trnh xl c enzyme c tht nng sut ln n 100%. Glucose sau c ln men thnh ethanol v kt hp vi ngun ethanol tqu trnh ln men xylose.


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Hn hp long ny sau c c c thnh ethanol c tnh cht nh nhin liu thngqua chng ct v tinh chsu nh l qu trnh hp php sut cao (PSA).

Phn on hemicellulose, thnh phn chnh thhai, chim khong 25%, chyu l xylan,cht c thddng chuyn ha thnh ng n xylose (hoc pentose). Xylose ng gpkhong 17% cc loi cy thn gv chim thnh phn chnh trong cc loi tho mc htkn. Do , vic ln men hoc chuyn ha xylose l cn thit cho qu trnh thng michuyn ha sinh hc lignocellulose thnh ethanol hoc cc ha cht sinh hc khc.Xylose kh c thbin i hoc ln men thnh ethanol hn so vi glucose, da trn mckhoa hc v cng nghhin ti. ng trn lp trng chbin, sc li hn khi tm

kim v pht trin mt loi vi sinh vt ti u c thln men cglucose v xylose thnhethanol trong cc thit bln men vi nng sut v chn lc cao. Cc phng php c ra nh sdng cc ging mi hoc cc loi men ci c bin cht, vi khun,v chbin kt hp cc enzyme v men ci. Mc d khng qu trnh ln men no hin tic thsdng trong thng mi, nhng c nhng pht trin ng kt c.

Lignin, thnh phn chnh th ba ca lignocellulose (khong 25%), l mt loipolymer gm nhiu vng thm khc nhau. Trong qu trnh chbin lignin, polymer bbgy thnh cc tiu phn c cha mt hoc hai vng thm. Oxy v cc chui phsbloi

bbng cc phng php xc tc; cc gc phenol sc cho phn ng vi methanol tothanh methyl aryl ether. Methyl aryl ethers, hay arylmethylethers, l nhng cht phgiac chsoctan cao c sdng pha trn vi xng.


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4.5. Cng nghethanol tcelluloseCc giai on khc nhau ca cng nghln men cellulose sn xut ethanol (hnh 4.5) sc lm r trong phn ny.

4.5.1. Thuphn acid, thuphn ho hcSthuphn cellulose bng acid c nghin cu v hiu mt cch tng i

t lu. Cc nhn t c trng quan trng trong s thu phn ho hc ny l t s bmt/th tch, nng acid, nhit , v thi gian. T sbmt /th tch c bit quantrng v cn quyt nh hiu sut glucose. V vy, kch cht cng nhcng tt cho thu

phn, xt vmt lng phn ng v tc phn ng [41]. i vi t lcht lng/chtrn, tlcng cao th phn ng cng nhanh. Mt scn bng phi c xem xt gia tlti uv tnh khthi kinh tbi v sgia tngtrong chi ph thit bsong song vi sgia tngvi tlcht lng/cht rn. i vi thy phn ha hc, tlcht lng/cht rn

ph hp nht l 10:1 [41].

Trong mt hthng thuphn ho hc cht thi cellulose tiu biu, cht thi cxay n kch thc ht mn. Vt liu xay c ngm trong acid yu (0,2-10%), nhit ca h huyn ph c nng ln 180 230 C, vi p sut trung bnh. Cui cng,cellulose thy phn c chuyn ha thnh ng. Tuy nhin, phn ng ny khng ctc dng trn lignin. Sn lng ng khc nhau, ty thuc vo bn cht ca cht thith. V d, 84-86% trng lng ca giy gi hng loi dy hoc 38-53% khi lng chtthi mt t c thc thu hi dng ng. Nng sut ng tng theonng axitcng nh nhit . Nng acid (H2SO4) ph hp l khong 0,5% so vi cht thi.

Mt qu trnh thuphn acid hai giai on, nhit thp, p sut mi trng, c sdng cc n vhot ng ring bit chuyn i hemicellulose v cellulose ln mencc loi ng c pht trin [42] v thnghim bi Tennessee Valley Authority(TVA) v BNng lng M (DOE). Phng th nghim v nh gi bench-scale chothy thu hi v hiu sut chuyn i ng tthn cy ng hn 90%. Nng sn

phm ng t c hn 10% glucose v 10% xylose. Cc cht c chtrong dung dchng khng bao givt qu 0,02 g/100 ml, xa di mc c chqu trnh ln men.Mt nh my th im thnghim c thit kv xy dng vo nm 1984.Nh my

thy phn axit th im cung cp ln men ng n mt c sln men v chng ct ccng sut 38 L / h c xy dng trong 1980. Cc kt qunghin cu ca hc tmtt nh sau.

Rm ng nghin n 2,5 cm l thch hp cho qu trnh thy phn cahemicellulose.


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Thi gian cn thit cho qu trnh thy phn ti u trong axit 10% 100 C l 2gi.

Hiu sut xylose tng cng l 86% v 93% thu c trong quy m bench-scale tithi gian phn ng l 1 v 3 gi.

Nc thi ti ch, acid long, v cc gii php tin thuphn axit n nh trongthi gian lu trvi ngy. Sy chn khng l thch hp trong qu trnh c c axit. Thuphn cellulose c thc hin thnh cng qu trnh un rm c cha 66-

78% acid trong su gi100 C. Hiu sut 75-99% cellulose chuyn ho thnhglucose thu c trong cc nghin cu trong phng th nghim.

Si nha thy tinh gia cbng nha vinyl ester c sdng chto bn chav ng ng.

4.5.1.1. M tqu trnh

Qu trnh ny sdng thy phn acid sulfuric hai giai on, nhit tng i thp, vcellulose c tin thuphn vi acid m c.

Hnh 4.6 l mt s qu trnh ca TVA. Rm ng c nghin v trn vi axitsulfuric long (khong 10% khi lng). Cc phn hemicellulose ca rm c chuynthnh ng pentose (xylose) bng cch nung nng dung dch n 100 C trong hai gil phn ng thy phn u tin. Rm ng th c cha khong 40% cellulose, 25%hemicellulose,v 25% lignin, da trn nguyn liu kh. Axit sunfuric cho phn ng thy

phn c cung cp bng cch ti ch cc dng sn phm tbc thy phn th hai,trong c axit sunfuric v ng hexose. Cc ng pentose v hexose, m chyu lxylose v glucose, c chit tcc thit bphn ng bng nc m. Nc chit giung sau c trung ha vi vi ( vi nung, CaO hoc dolomite nung, CaO MgO), lc loi bcc vt liu kt ta, v ln men sn xut ethanol [43].


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Hnh 4.6

M hnh thu phn acid nhit thp, p sut thp, hai giai on chuyn i ccnguyn liu khng g thnh ethanol. (Chnh sa tFarina, Barrier, v Forsythe, 1988.Modified from Farina, Barrier, and Forsythe, 1988. Fuel alcohol production fromagricultural lignocellulosic feedstocks, Energy Sources, 10: 231237.)

Cn rm tbc thy phn u tin (chuyn ho hemicellulose) c khncv chun bcho bc thy phn thhai (chuyn ho cellulose) bng cch ngm (bctin thuphn) trong acid sulfuric (nng khong 20-30%) tmt n hai gi. Phncn li c sau lc, khnc c hc, v sy chn khng lm tng nng acidn 75-80% trong pha lng trc khi vo thit bphn ng cellulose. Thit bphn ng

thy phn thhai hot ng 100 C v cn thi gian bn gi. Sn phm thit bphnng c lc loi bcc cht rn (chyu l lignin v cellulose khng phn ng). Vdng sn phm thit bphn ng thy phn thhai cha acid khong 10%, n c sdng trong bc thy phn u tin cung cp cc acid cn thit thy phnhemicellulose. Cn tcc thit bphn ng c ra sch thu hi cc acid sunfuriccn li v ng khng loi bc trong bc lc.


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Lignin l phn khng phn ng ca nguyn liu m c thc sdng tnh nhin liu l hi. N c mt gi trnhit khong 5.270 kcal/kg (hoc 9486 BTU/lb),so snh vi than subbituminous. Cc sn phm khc nh nh cht hot ng bmt, chtho do b tng, v cht kt dnh cng c thc to ra tlignin. B c thc s

dng sn xut mt ssn phm, bao gm ckh metan. Nghin cu s bcho thy, 30lt kh sinh hc c cha 60% metan c sn xut t mt lt b rm ng. Cho mi ltethanol sn xut, 10 lt b c sdng [42].

Tt ccc qu trnh ng ng, bn cha, v cc thit bphn ng tip xc viacid sulfuric n mn c lm bng si nha thy tinh gia cvinyl ester. My sy clm bng thp carbon v lt bng Kynar, mt nhn hiu ca Arkema Inc (trc y lAtofina), bng poly(vinylidene fluoride), hay PVDF. Bng ti cng c lm bng vtliu chng acid. Trc khuy thp mm c phmt lp Kynar hoc Teflon, thnghiu ca DuPont bng polytetrafluoroethylene, hay PTFE. Thit b trao i nhit cch to vi vng CPVC (poly clo(vinyl clorua)) v cun thp khng gCarpenter 20.Carpenter 20, cn c gi l hp kim 20, l mt hp kim Austenit nickel-st-crom c

pht trin cho schng n mn ti a i vi acid, c bit l acd sulfuric. Bm cch to vi hp cht lt Teflon khng kim loi, hoc thp khng gCarpenter 20. Haimy nn lc sdng tm polypropylene (PP) [42].

4.5.2. Thuphn enzymeL mt carbohydrate ln men, cellulose khc carbohydrate khc do thng c

sdng nh mt cht nn cho qu trnh ln men. Cellulose khng tan v c polymer

vi lin kt 1-4 -glucosidic. Mi phn tcellulose l mt polymer khng phn nhnh t15 n 10.000 n vD-glucose. Thy phn ca tinh thcellulose l mt bc kim sottc trong vic chuyn ho sinh khi thnh ethanol, bi v dung dch enzym trong ncgp kh khn trong vic phn ng vi cellulose khng ha tan, khng thm nc, v ccu trc cao. Do , to ra enzyme tan c hot ng trn cellulose khng ha tan lmt trong nhng thch thc chyu trong qu trnh pht trin ethanol tcellulose.

Cellulose cn phi c ha tan mt cch hiu qunh mt ng dn vo conng trao i cht ca tbo. Sha tan c thc hin bi enzyme thy phn xc tc

vi mt h thng cellulase ca vi khun v nm. Cellulase l mt loi enzym c snsut chyu do nm, vi khun, v protozoans, xc tc qu trnh thy phn ca cellulose,hay gi l cellulolysis, nh m tdi y.

4.5.2.1. Henzyme

C nhiu loi khc nhau ca cellulase, v chng khc nhau vc chv cu trc. Minhm vi khun cellulolytic c mt hthng enzyme c trng cho n. Khnng enzyme


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c thha tan dn xut cellulose c thc thy phn cellulose phc tp. Mc d ta bitrng chng l hn hp ca cc hp cht c khnng lm phn r cellulose nh cellulase,chng thc sl thp ca mt senzyme c bit. Da trn loi hnh cthca phnng xc tc, cc cellulase c thc m tthnh nm nhm ln, cthl,

1.

Endocellulase : phn ct lin kt ni ph vcu trc tinh thcellulose v chothy chui cellulose polysaccharide ring l.

2. Exocellulase : tch hai hoc bn n vsaccharide ttn cng cc chui tip xcvi sn xut bi endocellulase, cho ra disaccharides hoc tetrasaccharides, chnghn nh cellobiose. Cellobiose l mt disaccharide vi cng thc[HOCH2CHO(CHOH)3]2O. C hai loi chnh ca exocellulases, hay gi lcellobiohydrolases (CBH): (a) CBH-I hot ng tui khca cellulose v (b)CBH-II hot ng tui khng khca cellulose. Trong m tny, processivityl khnng ca mt loi enzyme tip tc lp i lp li chc nng xc tc ca n

m khng tch ra tn cht nn. Chnhmt enzyme hot ng c gitrn bmt ca mt cht rn nn, c hi phn ng c tng cng ng k.3. Beta-glucosidase : hoc cellobiase thy phn cc sn phm exocellulase,

disaccharides v tetrasaccharides, thnh monosacarit.4.

Oxidative cellulose : depolymerize v ph vcc phn tcellulose bi cc phnng gc t do, nh trong trng hp vi mt dehydrogenase cellobiose (chtnhn), l mt loi men xc tc cho phn ngcellobiose + chp nhn cellobiono-1,5-lacton + cht nhn khm cellobiose c dehydrogenated v cht nhn c kh.

5. Cellulose phosphorylases : depolymerize cellulose s dng phosphates thay chonc.

Trong hu ht cc trng hp, enzyme phc tp phn hy cellulose thnh beta-glucose. y l loi enzyme cellulase c sn xut chyu l do vi khun cng sinh. Vikhun cng sinh l vi khun sng cng sinh (tng tc gn v di hn) vi mt sinh vthoc loi khc. Enzyme thy phn hemicellulose thng gi l hemicellulase v vn cn

phbin xp di sau cellulase. Cc enzyme phn hy lignin l khng c phn loinh cellulase. Cng vi cc loi khc nhau cc enzyme, n phi c chra r rng rngmt thch thc chyu trong thy phn phn r sinh khi thnh ng ln men l lm

thno lm cho cc enzym khc nhau lm vic cng nhau nh mt hthng enzymethng nht. V d, cellulase v hemicellulases c tit ra tmt tbo nh enzyme tdo hoc cellulosomes ngoi bo (phc hp ca cc enzym cellulolytic c to ra bi vikhun). Cc hot ng chung ca cc enzym trong mt hthng l khnng c nhiuhot ng hn hot ng n lca mt loi enzyme bc lp.


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Cc enzym m t trn c thc phn thnh hai loi: lu tin (cn c gi lprocessive) v khng lu tin (hoc nonprocessive). Cellulase lu tin stip tc tngtc vi mt si polysaccharide n, trong khi cellulase khng lu tin stng tc mtln, gii phng, v sau tng tc mt si polysaccharide khc.

Da trn kh nng enzym, cellulase c c trng thnh hai nhm, c th lenzyme C1v enzyme CX[41]. Thnh phn C1c coi l mt "i lc" hay yu ttinthuphn bin i cellulose trt t cao (tinh th), (v d, si bng hoc Avicel) thnhmch thng v chui hydroglucose. Thnh phn C1t c tc dng trn cc dn xut hatan. Bng th gm 91% cellulose tinh khit. Nh vy, n phc vnh mt tin cht cnthit cho hot ng ca cc thnh phn CX. Nhn tCX(thy phn) phn hucc chuimch thng thnh carbohydrate ha tan, thng l cellobiose (disaccharide) v glucose(monosaccharide).

Vi sinh vt giu C1 l hu ch hn trong vic sn xut glucose tcellulose. Hnna, bi v giai on C1tin hnh chm hn so vi bc tip theo, l bc kim sottc . Trong srt nhiu vi khun, Trichoderma reesei vt qua tt ctrong vic shuC1phc tp. Trichoderma reesei l mt loi nm si cellulolytic cng nghip quan trngv c khnng tit ra mt lng ln cellulase v hemicellulases [44]. Tin bgn ytrong nguyn cu enzyme cellulase, cellulose thy phn (cellulolysis), tng cng sccng, nhn bn phn t, qu trnh thit kv k thut a T. reesei cellulase trthnh mt la chn thng mi khthi cho thy phn cellulose [45]. Cc tm hot ngca cellulolytic enzyme rt quan trng trong vic thit kcc hthng thy phn (nhn t

CX). Nu cc enzyme nm trong khi tbo, cc vt cht c phn ng phi khuch tnvo khi tbo. V vy, qu trnh thy phn enzyme cellulose thng din ra ngoi bo,ni m cc enzyme c khuch tn tkhi tbo vo mi trng bn ngoi.

Mt nhn tquan trng trong cc phn ng enzym l cc enzyme kiu thch nghay c bn. Mt enzyme c bn hin din trong tbo mi lc. Enzyme thch ng chc tm thy vi shin din ca mt cht nht nh, v stng hp cc enzyme ckch hot bi mt tc nhn khi mo. Hu ht cc nm cellulase l dng thch ng [15,41].

Cellobiose l mt tc nhn khi mo i vi Trichoderma reesei vi. Trong thct, ty theo hon cnh, cellobiose c thl mt cht c chhoc mt cht khi mo. Nl c chkhi nng vt qu 0,5 n 1,0%. Cellobiose l mt sn phm trung gian vthng c nng thp cho php n hot ng nh l mt cht khi mo lin tc[46].


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Mt ct mc thnh tu (2004) c ghi nhn bi Phng th nghim nng lng tito quc gia phi hp vi Genencor International v Biotech Novozyme l tm quantrng trong vic to ra cc enzym cellulase hiu qu, gim ng kchi ph, nh cptrong phn trc .

4.5.3. Qu trnh enzyme

Tt ccc qu trnh c bn enzym bao gm bn bc chnh c thkt hp trongnhiu cch khc nhau: tin xl, sn xut enzyme, thy phn, v qu trnh ln men, nhthhin trong hnh 4.7.

Hnh 4.7

Qu trnh thy phn enzyme nm. (Modified from Wright, 1988. Ethanol from biomassby enzymatic hydrolysis, Chem. Eng. Prog., 84: 6274.)

4.5.3.1. Tin xl

T lu ngi ta nhn ra rng mt s hnh thc tin x l l cn thit tc tc v nng sut hp l trong qu trnh thy phn enzyme ca sinh khi. Tin xl thng c thc hin gim kt tinh ca cellulose, gim bt mc ca phnng trng hp cellulose v vlignin-hemicellulose bao quanh cellulose, v lm gim btvic thiu din tch bmt c sn cho cc enzyme tn cng. Mt hthng tin xl inhnh bao gm vic gim kch thc, lm kn p sut, un nng, phn ng, gii phng psut, tng din tch bmt, v tch cht thy phn/cht rn [47].

Tin x l c hc nh xay xt nghin bi v nghin cun cng cao c nghincu nh mt cch tng din tch bmt, nhng n yu cu nng lng ln. Hiu qucacc qu trnh ha hc c th c tm hiu bng cch xem xt s tng tc gia ccenzym v bmt. Thy phn cellulose thnh ng v oligomer khc l mt phn ng

pha rn trong cc enzym phi bm vo bmt xc tc phn ng. Enzyme cellulase lprotein loi ln, vi trng lng phn tt30.000 n 60.000 v c cho l dng elip


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vi kch thc ln v nhnm trong khong 30 n 200 A . Din tch bmt bn trongca gl rt ln, tuy nhin, chc khong 20 % khi lng lxp cc phn tc kchthc cellulase c thxm nhp. Bng cch ph vcc ma trn cht chhemicelluloselignin, hemicellulose hoc lignin c thc tch ra v th tch xm nhp c thc

tng ln rt nhiu. Sloi bnguyn liu ny gip tng cng vic hp thenzyme.Vhemicellulose-lignin c thbph vbi xc tc acid hoc base. Cht xc tc

base ng thi loi b lignin v hemicellulose, nhng b tiu th phn ln base do btrung ha bi tro v nhm chc acid trong hemicellulose. Trong nhng nm gn y, sch c tp trung vo cc cht xc tc c tnh acid. Chng c thl acid khonghoc acid hu c to ti chbng cch tng thuphn hemicellulose.

Nhiu loi hnh tin x l c sdng chuyn i sinh khi. Tin x l c nghin cu trong nhng nm gn y l steam explosion autohydrolysis, qu trnh

oxy ha t (wet oxidation), organosolv, v thy phn hi nc nhanh (rapid steamhydrolysis - RASH). Mc tiu chnh ca hu ht cc phng php tin xl l tng nhy ca cellulose v lignocellulose vi acid v phn ng thy phn enzyme. Thy phnenzyme l mt phn ng ch thnhy vi depolymer ho lignin v xm nhp cellulose.H thng enzyme cellulase phn ng rt chm vi cc vt liu khng c x l, tuynhin, nu cc ro cn lignin xung quanh tbo thc vt bph humt phn, th tc thy phn enzyme c tng ln ng k.

Hu ht cc phng php tip cn tin xl khng c nh thy phn cellulose

thnh ng ha tan, m l to ra mt lng cn cellulose xl m ddng thyphn bng enzyme cellulase hn sinh khi tnhin. Qu trnh thy phn acid long hinang c xut cho mt snlc thng mi ha trong ngn hn cho n khi cc ch

phm cellulase thng mi chi ph thp trnn c sn. Qu trnh thy phn axit longnh vy thng dn n khng qu 60% hiu sut ng tcellulose.

4.5.3.1.1 Autohydrolysis Steam Explosion

Mt qu trnh autohydrolysis in hnh [48] s dng nc nng nn nhit khong 200 C di p sut cao hn p sut bo ha, do vic ginc nng trong phalng, thy phn hemicellulose trong vi pht. Thu hi hemicellulose thng cao, v

khng ging nh qu trnh acid xc tc, cht xc tc l khng cn thit. Qu trnh nyc thhin nh trong hnh 4.8. Qu trnh c nhit rt cao c thdn n nhit phnng k, to ra cc hp cht c ch. Tltc thy phn hemicellulose vi phn hung (nhit phn trong tnhin) l ln hn nhit cao. Qu trnh nhit thp cnng sut xylose thp hn v to nhiu sn phm phn huhn qu trnh nhit cao sdng cc ht nh, c kim sot tt.


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Theo mt nghin cu ca Dekker v Wallis [49], tin x l b ma bngautohydrolysis 200 C trong 4 pht v nph cu trc si (explosive defibration) dnn ha tan 90% hemicellulose (heteroxylan) v trong sn xut bt giy c nh gicao dbthy phn bi cellulase tTrichoderma reesei. Sn lng ng ha l 50% sau

24 gi50 C (pH 5,0) trong hp thenzyme c cha 10% (khi lng/thtch) bt bma v 20 n vblc giy cellulase (FPU), v sn lng ng ha c thc tngln n 80% ti 24 gibng vic bsung ngoi sinh -glucosidase tAspergillus niger.

Hnh 4.8

S qu trnh tin xl steam explosion. (Modified from Wright, 1988. Ethanol frombiomass by enzymatic hydrolysis, Chem. Eng. Prog., 84: 6274.)

Nhn chung, hiu sut xylose trong autohydrolysis thp (30-50%). Mt h thngautohydrolysis c sdng nh tin xl trong qu trnh thy phn v ln men ring

bit (SHF). Cc iu kin phn ng l 200C trong 10 pht, vi hiu sut xylose 35%.

Tiu thhi nc trong autohydrolysis phthuc rt nhiu vo m ca nguynliu ban u. Nguyn liu t i hi nng lng ng khn v lng nhit cao canc gi li. Mt li th quan trng ca autohydrolysis l n ph v lignin thnh ccmnh nhc thddng ha tan trong cbase hoc dung mi hu c.

Qu trnh steam explosion [50] c pht trin u tin vo nm 1925 snxut hardboard v gn y c p dng trn gdng trong u nhng nm 1980.


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Trong mt qu trnh steam explosion in hnh, vt liu cellulose c lm nng bnghi nc p sut cao (20 - 50 atm, 210 - 290 C) trong mt thi gian ngn (vi giy nvi pht). Khi p sut tin xl tng ln, cc phn tnc khuch tn vo cc cu trc vilxp (microporous) bn trong ca lignocellulose [47]. Trong qu trnh ny, mt shi

nc ngng tdi p sut cao, do lm t vt liu. Sau vt liu bt c ara khi thit bphn ng (y ra tthit bphn ng) thng qua mt vi phun nhvi psut khc. Do s st gim nhanh chng ca p sut, vt liu c y ra qua van x.Thut ng "explosion" c s dng do c tnh qu trnh gii phng vt liu vi sgim p t ngt ca hi nc.

4.5.3.1.2 Tin thuphn acid long

Hot ng chnhit thp hn vi vic khng t c bng cch thmmt lng nhaxit v c cho qu trnh tin xl. Cc acid lm tng tc phn ng nhit nht nh v tlca tc thy phn trn tc phn hucng tng ln.

C mt stng quan gia nhit phn ng v thi gian phn ng tn ti chocc phn ng xc tc acid. i vi autohydrolysis, khong iu kin kho st tvi gi100C n 10 giy 200C vi nng acid sulfuric 0,5 n 4,0%. Cht xc tc acidcng c sdng trong cc hthng steam explosion vi kt qutng t. Sn lngxylose thng khong 70-95 %. Tuy nhin, quy trnh acid sulfuric sn xut lignin thngc c hn (52% lignin chit c trong dung dch long NaOH) so vi sn xut bi mththng autohydrolysis. Sulfur dioxide cng c kho st nh l mt cht xc tc nng cao hiu quca tin xl. Sdng lng d nc lm tng tiu thnng lng v

gim nng ca xylose trong thy phn, do lm gim nng ethanol c thcsn xut trong bc qu trnh ln men xylose. Trong mt nghin cu ca Ojumu vOgunkunle [51], sn xut ng t c trong thit bphn ng gin on bng thy

phn lignocellulose vi axit nng rt thp (ELA) v iu kin nhit cao bi tin xl mn ca bi autohydrolysis ngay tu. Hiu sut ng ti a thu c c boco l 70% i vi mn ca xl trc 210 C pht mi tm ca th nghim. Gi trny l khong 1,4 ln so vi mc ng ti a thu c tmn ca khng c xltrong cng iu kin trn [51].

Qu trnh thy phn acid c mt lch slu di hn 100 nm. Nh mt sthay ththy phn acid long, qu trnh thy phn acid nng cao da trn cng c quan tmv c sn. Tuy nhin, cc loi quy trnh ny thng t tin hn hot ng v gpnhng kh khn trong kim sot [52]. Acid sulfuric l sla chn phbin nht ca chtxc tc, tuy nhin, cc axit v c khc nh hydrochloric, nitric v acid trifluoroacetic(CF3COOH) cng c sdng.


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4.5.3.1.3 Tin xl dung mi hu c (Organosolv Pretreatment)

Organosolv process l mt kthut nghin nho sdng dung mi hu c hatan lignin v hemicellulose. Qu trnh ny ln u tin c pht trin nh mt sthaythkhng c hi vi mi trng cho kraft pulping. u im chnh ca n bao gm vic

sn xut ca lignin cht lng cao tng gi tr, ddng phc hi v ti chdung mic sdng trong qu trnh ny, do lm gim p lc mi trng trn dng nc.

Trong loi tin xl lignocellulose ny, dung mi hu c (ethanol, butanol, hocmethanol) c thm vo phn ng x l s bha tan v loi bcc phn lignin.Trong thit bphn ng tin xl, cc lin kt ni ca lignin v hemicellulose (xem hnh4.1) bph vv chai phn u c thha tan, trong khi cellulose vn l mt cht rn.Sau khi ri khi thit b phn ng, cc phn hu c c loi b bng cch bay hi(chng ct) trong pha lng. Cc lignin sau kt ta v c thc ly ra bng cch lchoc ly tm. Nh vy, qu trnh ny phn tch sch nguyn liu thnh mt cn rn

cellulose, lignin rn qua ngng t, v mt dng c cha xylon lng, nh thhin tronghnh 4.9.

Qu trnh organosolv thng c thc hin nhit cao 140-230C di psut. Nhit cao c quyt nh bi cc phn ng ct t lin kt lin quan n vicgii phng lignin, v p sut cao l cn thit gicho qu trnh hot ng ca dung mitrong giai on lng. Ethanol c coi nh mt dung mi thun li nht organosolv dogi thnh thp, tnh sn c v ddng thu hi dung mi. Butanol, cng kh ha hn vkhnng vt tri cho hiu sut lignin cao v khng tan trong nc, do vic thu hi

dung mi n gin v khng cn tn nng lng chng ct. Mc d hiu quca butanoll kh hp dn, nhng chi ph kh t. Nh gii thch, mi quan tm chnh trong ccqu trnh ny l thu hi hon ton dung mi, vic ny nh hng n chi ph tng th;nh vy, quy trnh kthut v ti u ha trthnh yu tquan trng ca qu trnh kinh tca organosolv.

Kt qucho thy mt sphn ng xy ra trong qu trnh organosolv nh hng mnhn tc enzyme ho [53]. Nhng phn ng ny c thdo nhng thay i l ho tronglignin hoc cellulose.


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Hnh 4.9

Qu trnh tin xl Organosolv. (Modified from Wright, 1988. Ethanol from biomass byenzymatic hydrolysis, Chem. Eng. Prog., 84: 6274.)

Nhn chung, qu trnh organosolv cho nng sut cao hn so vi mt squ trnhkhc do nh hng ca dung mi hu c trn ng hc thy phn. Trong mt nghin cugn y, Pan et al. [54] p dng tin xl organosolv vi ethanol vi nhng cy thngLodgepole cht do bcnh cng ni v qu trnh ny t c 97% chuyn ho glucose.Hthu hi 79% lignin trong iu kin 170C, 1.1% khi lng H2SO4, v 65% thtchethanol trong thi gian 60 pht.

4.5.3.1.4 Kt hp tin xl RASH v Organosolv

Thnghim c tin hnh nng cao hiu sut tng thbng cch kt hp haiqu trnh tin xl c lp bao gm thy phn nhanh hi nc v organosolv. Rughaniv McGinnis [53] nghin cu nh hng ca vic kt hp RASH - Organosolv datrn tlthy phn enzyme v hiu sut ca lignin v hemicellulose ha tan. S qutrnh ny thhin trong hnh 4.10. Khi tin xl organosolv, my to hi nc c ngtv cc van ngng tng. Phn cn li vic thit lp thit bphn ng tng tnh quytrnh RASH.


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Hnh 4.10

S kt hp RASH v tin xl organosolv. (Modified from Rughani and McGinnis,

1989. Combined rapid steam hydrolysis and organosolv pretreatment of mixed southernhardwoods, Biotechnol. Bioeng, 33: 681686,)

Qu trnh organosolv nhit thp thng khng hiu qu trong vic loi b lignin,nh gii thch trc ; tuy nhin, kt hp hai qu trnh dn n tng sha tan ligninv hemicellulose. Nhit RASH l yu t chnh trong vic ti a ha t l cellulosetrong sn phm cui cng. Nng sut ti a ca lignin ho tan t c ti nhit 240 C cho RASH v 160 C cho qu trnh organosolv.

4.5.3.1.5 Tin xl cht lng ion

Cht lng ion l mt loi dung mi mi m gn y c sdng phbin nhmt la chn thay ththn thin mi trng cho dung mi hu c. Mt cht lng ion lmui bao gm cc anion v cation km tng tc v im nng chy thng di 100C.Cht lng ion hay cn gi l cht lng in ly, ion nng chy, mui lng ion, thutinhion....C hng ngn cht thuc nhm ny. Cht lng ion c chng minh l dung mi


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rt hiu qutrong cc lnh vc hydro ha, este ha, tng hp vt liu nano, xc tc sinhhc, v trch ly c chn lc cc cht thm[55, 56].

Spht trin ca cng ngh tin x l sinh khi sdng cht lng ion chmic nghin cu. Cng trnh u tin chng minh cht lng ion nh mt dung mi

cellulose trong iu kin x l m du c bo co trong nm 2002 ca Swatloski[56]. Trong cc th nghim s dng mt lot cc anion v cation 1-butyl-3-methylimidazolium, mt scht lng ion c thha tan hon ton vi tinh thcellulose,v cellulose c thu hi thng qua vic b sung mt s cht k dung mi(antisolvent) nh nc hoc ethanol. Hn na, sn phm thu hi c th c ti sinhthnh nhng hnh dng khc nhau. Dung mi cellulose hiu qunht l cht lng ion ccha cc anion chloride. Pht hin quan trng ny kt hp vi phng php tin x lmi mang li kt qu l cc enzyme c th thuphn hiu quhn to thnh glucose,cellulose v nh hnh c to ra bi cht lng ion nhiu hn vi tinh thcellulose ctm thy trong lignocellulose tnhin [55, 57].

Cht lng ion l mt hng nghin cu th vca nn khoa hc v shu nhiuthnh tu trong vic tin x l lignocellulose. Nhiu cng vic R & D chuyn su cnc thc hin trc khi qu trnh thng mi ho c pht trin v khai thc y .

4.5.3.2Sn xutvc chenzymeEnzyme quan tm l cellulase, cn thit cho qu trnh thy phn ca cellulose cn

gi l cellulolysis. Cellulase l mt hthng enzyme a thnhphn bao gm endo--1,4-

glycanases, exo--1,4-glucan glucohydrolases, v exo--1, 4 - glucan cellobiohydrolase.Cellobiose l sn phm cho ca hthng ny nhng li c chcao i vi enzym vkhng th s dng bi hu ht cc sinh vt. Cellobiase thy phn cellobiose thnhglucose t c chv ln men cao. Nhiu loi nm sn xut ra cellobiase ny v hu htcc nghin cu m hin nay ang c thc hin l trn Trichoderma reesei (viride). Cccellulase c sn xut bi T. reesei l t c chhn cellulase khc, v vy c li thlncho cc mc chcng nghip [58].

Cc loi c chbi cellulase l chca nhiu cuc tranh lun trong nghin cu.Mc d hu ht cc nh nghin cu ng hc chcnh tranh (competitive) [59-64] , mts cellulase l khng cnh tranh (noncompetitive) [46, 62, 65, 66] hoc khng c chcnh tranh (uncompetitive) [60]. c chuncompetitive xy ra khi cht c chenzyme chlin kt vi phc hp hnh thnh gia cc enzyme v c cht, trong khi c chnoncompetitive xy ra khi cht c chenzyme v c cht u lin kt vi enzyme btkthi im no. Trn cht nn nh Solka Floc (cellulose tinh khit), rm la m, vbma (sinh khi cn li sau khi thn cy ma bnghin nt trch xut nc tri cy), vic


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Trichoderma reesei to enzyme bc chcnh tranh bi glucose v cellobiose. Mt khc,mt senzyme l c chnoncompetitive bi cellobiose khi s dng c cht khc nhrm rv Avicel. Avicel l mt tn thng mi c ng k cho cellulose vi tinh th c thy phn mt phn bng acid v nghin thnh bt mn; n c sdng nh

mt cht thay thcht bo. Trichoderma viride c c chuncompetitively bi glucosetrong cht nn b bng [60].

Nhiu t bin c to ra da trn Trichoderma reesei . Ni bt nht trong sny l Rut C -30 [67], t bin u tin to ra -glucosidase [43]. Li thkhc ca st bin bao gm kh nng siu sn xut (hyperproducing) v khnng chng c chcarbon (carbolite-repression resistant). Thut nghyperproduction c ngha l sn xutqu mc.

Cellulase t vi khun a nhit cng c nh gi rng ri. Trong s ,

Clostridium thermocellum c coi l sinh vt c trng. C. thermocellum l mt vikhun k kh, a nhit, phn hu cellulose (cellulolytic) v sn sinh ethanol(ethanogenic), ngha l c khnng chuyn i trc tip cht nn cellulose thnh ethanol.Cc enzyme phn tch tvi khun a nhit c tnh bn nhit cao v do chng c thsng st thm na thi gian sng khi nhit cao. Mc d y khng phi l trnghp phbin, cellulase tch ra tClostridium thermocellum c hot ring bit cao[68], c bit l i vi cc dng tinh thca cellulose chng tc khnng chngshnh thnh cellulase.

Sn xut enzyme vi Trichoderma reesei l kh khn v s sn sinh cellulase lgin on trong shin din ca cc cht nn dchuyn ho. V vy, hu ht cc nghincu sn xut c tin hnh trn ngun carbon khng ha tan nh sinh khi steam-exploded hoc Solka-Floc [69]. Solka-Floc cha beta-1,4-glucan, c mu trng, khngmi v khng thm, v c kch thc ht a dng [70]. Trong hthng nh vy, tc tng trng v sn sinh cellulase gii hn bi v cc loi nm phi tit ra cellulase vthc hin thy phn enzyme chm phn rn c c carbon cn thit. Nng sut trung

bnh t c khong l00 IU/L/gi. [Hot ng thy phn ca cellulose thng sdngn vlc quc t(international filter unit - IU). y l mt n vxc nh lng ng

sn xut trong mt n vthi gian tmt di giy lc Whatman]. Cc n vgiy lc lmt thc oskt hp hot ng ca ba loi enzyme trn cht nn. Nng sut cao c bo co vi Trichoderma reesei t bin trong mt h thng fed-batch s dnglactose nhmt ngun carbon v gdng steam-exploded nh mt cht cm ng. Mcd lactose khng c s lng cung cp mt ngnh cng nghip sn xut ethanolquy m ln, nhng iu ny gi cho vic c thto ra nhng ging bin i c thsnxut cellulase vi ngun carbon ha tan nh xylose v glucose.


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Nng sut tng lm gim ng kkch thc v chi ph ca men c sdng sn xut cc enzyme. Cng nghln men nhanh hn cng slm gim nguy c nhimv c thcho php xy dng t tn km hn. Ngoi ra, sdng mt cht nn ha tan cthcho php n gin ha thit kquy trnh ln men hoc cho php cc thit kca mt

hthng sn xut enzyme lin tc. Enzyme chi ph thp nhng hiu qucho cng nghsn xut ethanol tlignocellulose phi c pht trin lm gim chi ph hot ng vnng cao nng sut ca qu trnh.

4.5.3.3 Thy phn cellulose

4.5.3.3.1 Hp phenzyme cellulase

Qu trnh thy phn enzyme ca cellulose tin hnh bng vic hp ph enzymecellulase trn cn lignacious cng nh cc phn cellulose. Hp ph trn cn lignaciouscng rt th vnhn trn quan im thu hi enzyme sau khi phn ng v ti sdng n

trn cht nn mi. R rng, hiu quthu hi bgim bi shp thca enzyme trn cnlignacious, bi v mt phn ln trong tng chi ph hot ng l do vic sn xut ccenzyme. Khnng ca cn lignacious hp thcc enzyme chu nh hng ca cc iukin tin xl, do tin xl cn c nh gi, hn na bao nhiu enzyme hp phtrn cn lignacious vo cui qu trnh thy phn cng nh hng n tc v mc

phn ng thy phn.

Shp thca cellulase trn cn cellulose v lignacious c nghin cu biOoshima, Burns v Converse [71] sdng cellulase tTrichoderma reesei v gcng xl trc bng acid sulfuric long vi phn hy explosive. Cellulase c thy l hp thtrn cn lignacious cng nh trn cellulose trong qu trnh thy phn ca tin xl g.Sst gim trong mc thu hi enzyme trong giai on lng cng vi stng nng cht nn c bo co l do hp phtrn cn lignacious. Khnng hp phenzymeca cn lignacious gim khi nhit tin xl c tng ln, trong khi khnng cacellulose tng khi nhit cao hn. Gim lng enzyme hp ph trn cn lignaciouscng nh tng nhit tin xl l iu cn thit ci thin qu trnh thu hi cui cngca enzyme cng nh tng cng tc v mc thy phn enzyme. Lu et al. (2002) tin hnh thnghim hp phcellulase v nh gi ti sinh enzyme trong qu trnhthy phn steam-exploded cy linh sam Douglas vi xc tc SO

2 v hu x l steam-

exploded cht nn linh sam Douglas [72]. Sau khi hu xl kim peroxide nng, tc v hiu sut thy phn t c tcc cy linh sam Douglas hu xl cao hn ng k,ngay c lng enzyme t hn, so vi nhng cng trnh thu c vi steam-explodedtng ng sdng cy linh sam Douglas. Cng trnh ny cho thy sthu hi v ti sdng enzyme trong qu trnh thy phn cht gmm hu xl a ra kt qut cn thitvic bsung cc enzyme mi trong qu trnh chuyn ho sinh hc gmm [72].


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Mt qu trnh thy phn enzyme lin quan n vt liu lignocellulose rn c thc thit k theo nhiu cch. Mu schung l cc cht nn v enzyme c a voqu trnh ny, v dng sn phm (dung dch ng), cng vi mt d lng rn, ri khiquy trnh ti cc im khc nhau. Cn c cha cc enzyme bhp thbmt khi cn c

loi bkhi hthng.m bo rng qu trnh thy phn enzyme t hiu qukinh t, mt mc

thu hi enzyme nht nh l cn thit. Enzyme ho tan v enzyme hp phtrn cn chtnn phi c tn dng li. Ngi ta cho rng smt mt ca enzyme bnh hng bivic la chn cc giai on m ti cc enzyme trong dung dch v cc enzyme hp phti tun hon v im m cn c ly ra khi hthng. Vallander v Erikkson [46] nhngha mt hm mt mt enzyme L, giskhng c tn tht xy ra thng qua lc:

H pht trin mt s m hnh l thuyt kt lun rng s tng hp phenzyme dn n stng mt mt enzyme. Lng enzyme mt mt gim nu cn rnc loi bvo cui qu trnh. Enzyme hp thv ha tan nn c ti bsung ti im

bt u ca qu trnh. iu ny c bit quan trng i vi enzyme ho tan. Ra ton bcn dn n khnng thu hi thp hn cc enzyme hp thhn l nu phn ln (60%hoc nhiu hn) cn vi enzyme hp thc ti tun hon. Qu trnh thy phn khnggin on trong mt khong thi gian nht nh dn n mc ng ha thp hn hn

l khi thy phn c thc hin nhiu ln. ng ha cng l u tin nu cn c ly ragiai on cui. Nghin cu thc nghim cc m hnh thy phn l thuyt thu hihn 70% enzyme [46].

4.5.3.3.2 C chthy phn

Qu trnh thy phn tng th da trn cc hnh ng tng hp ca ba enzymecellulose ring bit v phthuc vo tlnng v tlhp phca cc enzyme thnh

phn: endo--glucanase, exo--glucanase, v -glucosidases. Endo--glucanase tn cngcu trc trong ca cellulose polymer mt cch ngu nhin [43], to u chui mi. Doenzyme ny xc tc phn ng pha rn, n hp ph mnh nhng thun nghch vi

cellulose vi tinh th (cn gi l Avicel). Cng hp th ln hn nhit thp.Enzyme ny cn thit thy phn cht nn tinh th. Thy phn cellulose c kt quchora s tch ly ng k ca ng kh, ch yu l cellobiose, bi v phc hp cellulasengoi bo khng c hot ng ca cellobiose. ng c cha nhm aldehyde c oxyha thnh axit cacboxylic c phn loi l ng kh.


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Exo--glucanase loi bcc n vcellobiose (trong c disaccharides vi cngthc ([HOCH2CHO(CHOH)3]2O) t phn kt thc khng kh ca chui cellulose. ycng l mt phn ng pha rn, v exo--glucanase hp thmnh trn ccht nn tinh thv v nh hnh. C chca phn ng l phc tp bi v c hai hnh thc khc bit ca

endo- v exo-enzyme, mi loi c mt kiu tng hp khc nhau vi cc thnh phnkhc ca phc hp. Nu cc enzyme tip tc phn tch cc n vcellobiose, nng cellobiose trong dung dch tng ln. Hot ng ca exo--glucanase c th b c chnghim trng hoc thm ch ngng li do stch ly cellobiose trong dung dch.

Cellobiose c thy phn thnh glucose do tc ng ca -glucosidase.Glucosidase l bt k enzyme no xc tc thy phn glucoside. -glucosidase xc tcthy phn cn cui, khng khbeta-Dglucose v gii phng beta-D-glucose. nh hngca -glucosidase ln kh nng ca phc hp cellulase phn gii Avicel cnghin cu bi Kadam v Demain [73]. H xc nh cc c trng cht nn ca -glucosidase v chng minh rng vic b sung chng vo phc hp cellulase s tngcng qu trnh thy phn Avicel, cthbng cch loi bcc cellobiose tch ly. Mtdng bn nhit ca -glucosidase, Clostridium thermocellum, c th hin trongEscherichia coli, c sdng xc nh cc c trng cht nn ca enzyme. Thy

phn cellobiose thnh glucose l mt phn ng pha lng v -glucosidase hp phhocrt nhanh hoc khng hp thtrn cht nn cellulose. Tc ng ca -glucosidase c th

bchm hoc dng li bi sc chca glucose tch ly trong dung dch. Stch tnycng c thlm ton bqu trnh thy phn ngng li do sc ch-glucosidase bngstch tca cellobiose, m ln lt c chhot ng ca exo-glucanase. Qu trnh thy

phn ca vt liu cellulose ph thuc vo shin din ca cba loi enzim vi lngthch hp. Nu c mt trong nhng enzyme c mt t hn so vi lng yu cu, nhngenzyme khc sbc chhoc thiu cht nn cn thit hot ng.

Tc thy phn thng tng khi tng nhit . Tuy nhin, do hot xc tc caenzyme lin quan n hnh dng ca chng, sbin dng ca enzyme nhit cao cthlm bt hot hoc ph hy cc enzyme. cn bng gia gia tng hot v tng xuhng bt hot, vic thy phn nm men thc hin thch hp khong 40-50C.

Mc d thy phn enzyme c thc hin tt nhit thp 40-50C, thy phnacid long c thc hin ti nhit cao hn. Cc nh nghin cu ti Phng th nghimNng lng ti to Quc gia (NREL) bo co kt qucho mt qu trnh thy phn acidlong gmm trong cc iu kin ca cc l phn ng nhsau [74].

1. Giai on 1: acid sulfuric 0,7%, 190C, thi gian lu 3 pht


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2. Giai on 2: acid sulfuric 0,4%, 215C, thi gian lu 3 pht

Kim tra quy m bench-scale khng nh tim nng t c hiu sut 89% chomannose, 82% cho galactose, v 50% i vi glucose. Ln men vi Saccharomycescerevisiae t c chuyn ho ethanol n 90% hiu sut l thuyt [75].

4.5.3.4 Ln men

4.5.3.4.1 Thy phn v ln men ring bit (SHF)

Thy phn Cellulose v ln men c ththc hin tqu trnh khc nhau, ty thucvo giai on m qu trnh ln men c thc sthc hin theo trnh tquy trnh: (l)thy phn v ln men ring bit, SHF, hoc (2) ng ha vln men ng thi, SSF.Cc tvit tt "SHF" v "SSF" c sdng rt thng dng trong lnh vc ny.

Trong SHF, qu trnh thy phn c thc hin trong mt bnh cha v dchthy

phn sau c ln men trong mt thit bphn ng thhai. Cc mt t tin nhttrong ton bchi ph qu trnh l chi ph nguyn liu, sn xut enzyme, thy phn, v cctin ch. Chi ph nguyn liu v tin ch cao v chc khong 73% cellulose c chuynthnh ethanol trong 48 gi, v phn cn li ca cellulose, hemicellulose v lignin btchy hoc kh ha. Sn xut enzyme l mt bc tn km do slng ln cc enzymec sdng vt qua sc chsn phm cui cng cng nh do tc phn ngchm.

Bc thy phn cng tn km do ngun vn ln v chi ph hot ng ln (do bn

cha v thng khuy c kch thc ln). Cc thng squan trng nht l nng sut thyphn, cht lng sn phm, v lng enzyme cn thit, tt cu lin quan n nhau.Nng sut thng cao hn tronghthng long ni m vic c chcc enzym caglucose v cellobiose c gim thiu. Tng lng enzyme c thgip khc phc scchv tng nng sut v nng , mc d vic ny chc chn lm tng chi ph tng th.Tng thi gian phn ng cng lm cho sn lng v nng cao hn.

Enzyme cellulase tsinh vt khc nhau c thdn n tc ng khc nhau r rt.Hnh 4.11 cho thy nh hng ca hiu sut lin tc 1 lngcht rn v enzyme cnhv tc ng khi lng enzyme khc nhau. Tng lng enzyme vt qu mt im cth

lm cho n khng cn c tc dng. Sl kinh tkhi hot ng lng enzyme ti thiu.Hoc, cc enzyme c thc ti chbng cc phng php thch hp. Nh cellulosec thy phn, thnh phn endo-v exoglucanase c a trli vo dung dch. V ilc i vi cellulose, cc enzyme c thc phc hi v ti sdng bng cch cho dchthy phn tip xc vi ngun nguyn liu u vo sch.


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Lng thu hi l hn chv -glucosidase, khng hp thvo nguyn liu uvo. Mt scc enzyme vn cn gn lin vi lignin v cellulose khng phn ng, ngoira, enzyme bbin tnh nhit trong qu trnh thy phn. Mt kh khn ln trong qu trnhny l qu trnh c duy tr tnh v trng, nu khng, hthng qu trnh sb nhim.

Nng lng tiu thtrong vic khuy cng quan trng v nh hng n kinh tca qutrnh ny [43]. Mc d nh hng ca sn lng trn gi bn ca ethanol trong hnh danhiu hnvoquy trnh sn xut ethanol cin, n gii thch tm quan trng ca nngsut trn chi ph sn phm cui cng.

Um v Hanley [69] tin hnh mt nghin cu thc nghim vqu trnh thy phn v lnmen enzyme rn ca Solka floc thnh ethanol. gim chi phchng ct ethanol ca dchln men th snng glucose ban u cao. Tuy nhin, sgia tng nng glucose

thng lm gim nng sut ethanol do gim khi lng v tc truyn nhit.khc phc skhng tng thch nhit gia cc qu trnh thy phn enzyme

(50C) v ln men (30C), ng ha, tip theo l qu trnh ln men (SFF), c sdng vi nng rn tng i cao (10% n 20%) sdng phng php phn khnglng . Glucose v ethanol c sn xut tSolka floc, u tin c phn hy bi ccenzyme 50 C trong 48 gi, tip theo l qu trnh ln men.


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Trong qu trnh ny, cc enzyme thng mi c sdng kt hp vi mt chngti thp ca Zymomonas Mobilis. Sn lng ethanol cao nht 83,6%, 73,4%, v 21,8%,da trn lng l thuyt ca gluxose, thu c vi nng cht nn tng ng l10%, 15% v 20%. Nhng gi trny l 80,5%, 68,6%, v 19,1% khi da trn slng

l thuyt ca sinh khi tbo v glucose ha tanhin din sau 48 giSFF. Ngoi nhngnh hng nng cht nn, hcng iu tra nhng nh hng ca cu hnh thit bphn ng [69].

Nh mt nghin cu cin c chca qu trnh thy phn enzyme cellulose,Fan, Lee, v Beardmore iu tra nhng nh hng ca c im cu trc chnh cacellulose trn thy phn enzym. Hpht hin ra rng tc thy phn l chyu phthuc votrt tcu trc ca cellulose c thc i din tt nht bng kt tinh hnl din tch bmt [76].

4.5.3.4.2 ng ha v ln men ng thi (SSF)Chi ph hot ng ca qu trnh SSF ni chung l thp hn so vi SHF min l qu

trnh c hip ng thc hin. Nh tn ca qu trnh, chai qu trnh thy phn v lnmen c thc hin trong cng 1 thit b. Trong qu trnh ny, men ln men glucosethnh ethanol ngay sau khi glucose c sn xut, do ngn nga cc loi ng ttchly v gy ra sc chsn phm cui cng. Sdng men, Candida brassicae, v enzymeGenencor (bi Genencor International), nng sut tng ln 79% vnng ethanol snxut l 3,7% [43, 77].

Ngay ctrong SSF, cellobiose (ng disaccharide ha tan) sc chxy ra mc ng k. Lng enzyme cho SSF l chc 7 IU / g cellulose, so vi 33 IU / gtrong SHF. Chi ph nng lng v nguyn liu c phn gim v nng sut c ci thin,v nng ethanol tng lm gim ng kchi ph chng ct v tin ch sdng

Chi ph ca qu trnh SSF l hi t hn so vi chi ph kt hp thy phn v lnmen trong qu trnh SHF. Cc yu tgim ca thtch l phn ng do nng ethanolcao hn b p cc yu ttng kch thc l phn ng do thi gian phn ng di hn (7ngy i vi SSF vs 2 ngy i vi thy phn v 2 ngy cho ln men). Nghin cu trc cho thy qu trnh ln men l bc quyt nh tc cn qu trnh thy phn enzyme

th khng. Vi nhng tin bv pht trin gn y trong chng nm men ti thp ckhnng ln men hiu qucglucose v xylose, sxem xt cu hnh cho khai thcthng mi, cng nh vic xc nhtcgii hn cho quy trnh cng nghtng th, cthphi thay i cho ph hp.

Qu trnh thy phn c thc hin 37 C v tng nhit lm tng tc phnng, tuy nhin, nhit trn thng bhn chbi khnng tn ti tbo nm men.


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Nng ethanol cng l mt yu thn ch. (iu ny c thnghim bng cchkt ni mt n vphn tch vi thit bphn ng SSF v loi bcc ethanol theo nhk. Kthut ny cho thy nng sut ln n cao hn 44%. )

Hon lu cc cht rn cn li cng c thlm tng nng sut qu trnh . Tuy nhin

, hn chquan trng nht trong ti chenzyme n tshin din ca lignin , l trvi enzyme . Tlhi lu cao tng lignin rong l phn ng v gy ra kh khn trong xl.

Hai loi chnh ca qu trnh ti chenzyme c xut: mt l cc enzymec thu hi trong pha lng v hai l enzyme c thu hi bng cchhon lu cc chtrn khng phn ng [ 43 ] . Hthng ca loi u tin c xut cho qu trnh SHFhot ng 50 C. Cc hthng ny c a chung nhit cao nh vy bi v nhittng lm tng tlenzyme trong phalng. Ngc li, khi nhit gim, lng

enzyme hp phtrn cht rn tng. Do , nhit thpnh trong qu trnh SSF, tichli cht rn trthnh mt la chn hiu quhn.

4.5.3.4.3 So snh gia 2 qu trnh SSF v SHF

Hthng SSF cung cp li thln hn SHF xl nhgim sc chtrong snphm cui cng ca phc hp enzyme cellulase. Qu trnh SSF cho nng sut cao hn sovi SHF (88% so vi 73% trong mt v dtrc ) v lm tng ng knng sn

phm (nng glucose tng ng 10%, so vi 4,4%). Li thquan trng nht ca qutrnh SSF l lng enzyme sdng, c thc gim t33 xung 7 IU / g xenlulo, iuny ct gim chi ph ca ethanol ng k. Vi spht trin lin tc ca cc enzym chi phthp, cc phn tch so snh ca hai qu trnh chc chn sthay i. Mt nghin cu sosnh cc chi ph tng i ca hai quy trnh c cng btrong bi bo ca Wrightnm 1988 [43].

Kt qucho thy, trn c sgi bn c tnh tethanol cng sut 25.000.000gallon / nm, SSF l hiu quvmt chi ph hn SHF theo hs1:1.49, l $ SHF / $SSF = 1.49. Cn lu r rng rng sliu trch dn y l tlca hai gi, khngphitrc tip l gi tin trn gi bn ethanol. Hn na, nghin cu ny cng c da trn ccenzym v cng nghchuyn ha sinh hc c sn trong gia nhng nm 1980, l khc

nhau ng kso vi cng nghtin tin nht hin nay ca thkXXI. Tuy nhin, vic sosnh chi ph sn xut ethanol gia hai cu hnh qu trnh khc nhau cung cp mt tngvsmi tng quan phc tp ca cc yu tchi ph nh tc phn ng, nhit , thigian xl, hp phenzyme, lng enzyme v khnng thu hi, c chsn phm vnhiu hn na.


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Vi nhng l do kinh tging nhau ca qu trnh, ngi ta don rng lai ghpthy phn v ln men cu hnh qu trnh (HHF) sc chp nhn rng ri nh l mtqu trnh c la chn cho sn xut ca nhin liu ethanol lignocellulose, bt u bngmt bc tin thy phn ring bit v kt thc l qu trnh ng ha ng thi (thy

phn) v bc ln men. Trong giai on u tin ca qu trnh thy phn, nhit caong hacellular enzyme din ra, trong khi giai on thhai ca SSF, thy phnenzyme mesophilic (nhit trung bnh) v ln men enzyme ng sinh khi din racng mt lc. Vic ti u ha cu hnh qu trnh sphi thay i nu mt enzyme cth,chng minh l c hiu qucao v chi ph-hiu qu, c tm thy l khng chu c vithuc c chnht nh c lin quan n bt kcc bc xl.

4.5.3.5 Sln men xylose

Trong trng hp xylose chim 30-60% ca cc loi ng ln men trong sinhkhi gcng v thn tho, qu trnh ln men ca xylose thnh ethanol trthnh mt vn

quan trng. Hiu ququ trnh ln men xylose v cc thnh phn hemicellulose khcl cn thit cho spht trin ca mt qu trnh hiu qukinh tsn xut ethanol tsinh khi lignocellulose. Khng cn phi ni, ng ln men ca cglucose v xylose chiu qucao l iu mong mun nht. Nh tho lun trc , ln men xylose

Nh tho lun trc , ln men xylose sdng men pentose c chngminh l kh khn do mt syu tbao gm cc yu cu vO2 trong sn xut ethanol,c tnh acetate, v to thnh sn phm phnh xylitol. Xylitol (hoc, xyletol) l mthp cht tnhin t ng c tnh anticariogenic (ngn nga su rng).

Phng php tip cn khc ln men xylose bao gm vic chuyn ha xylosethnh xylulose (mt ng pentose, mt phn ca qu trnh chuyn ha carbohydrate,c tm thy trong nc tiu ca cc c thvi iu kin pentosuria [78]) sdngxylose isomerase trc khi ln men bng nm men Saccharomyces cerevisiae, v phttrin cc chng bin i gen [79].

Mt phng php tch hp ln men xylose vo ton bqu trnh c minh hatrong hnh 4.12. Trong v dny, thy phn axit long c xem nh l mt bc tin xl. Dng cht lng c trung ha loi bbt kacid khong hoc acid hu c gii

phng trong qu trnh tin xl, v sau n giai on ln men xylose. Nc thm votrc khi ln men, nu cn thit, c thsdng y cc cht nn m nng sut khng

bgii hn bi sc chsn phm cui cng. Dng ethanol long tqu trnh ln menxylose sau c sdng cung cp nc pha long cho hn hp cellulose lignin voSSF. Nh vy, nc vo trong qu trnh tin xl c sdng trong chai qu trnhln men xylose v qu trnh SSF.


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Vic chuyn ha xylose thnh ethanol bng ti thp E. coli c nghin cutrong bln men iu khin pH [80]. Nng tng i cao ca ethanol (56 g / L) csn xut txylose vi hiu qutt.

Ngoi xylose, tt ccc thnh phn ng khc ca sinh khi, bao gm glucose,mannose, arabinose v galactose, c thc chuyn ha hiu quthnh ethanol bng E.coli ti thp. Khng oxy cng khng duy tr nghim ngt cc iu kin ym kh l cnthit cho sn xut ethanol ca E. coli. Tuy nhin, vic bsung c sngn chn qutrnh axit ha qu mc l iu cn thit. Mc d t c sl cn thit duy tr iu kin

pH thp, hiu sut ethanol thp v qu trnh ln men chm hn c quan st dipH=6. Ngoi ra vic bsung cc ion kim loi, chng hn nh canxi, magi, v cc ion

kim loi mu, kch thch sn xut ethanol [80].Nhn chung, qu trnh ln men xylose khng yu cu kim sot nhit chnh xc,

min l nhit c duy tr t25 n 40 C. Nng xylose cao nh 140 g / L c thnghim mt cch tch cc nh gi mc m ng ny c chstngtrng v qu trnh ln men. Nng cao hn lm chm stng trng v qu trnh lnmen ng k. Ingram v ng nghip [80-83] chng minh rng Escherichia coli ti t


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hp thhin plasmid-borne Zymomonas Mobilis gen pyruvate decarboxylase (PDC) valcohol dehydrogenase II (ADHII; adhB) c thchuyn hahiu quchexose v ng

pentose sn xut ethanol. Ethanologenic E. coli i hi iu kin ln men n ginhn, to ra nng cao hn ca ethanol, v hiu quhn cc loi men pentose-ln men

sn xut ethanol txylose v arabinose [84].Mt nghin cu ca Sedlak, Edenberg, v Ho [28] pht trin thnh cng kthut

di truyn men Saccharomyces c thln men ng thi glucose v xylose thnh ethanol.Theo kt quth nghim ca h, sau khi tiu thnhanh chng glucose trong vng chay 10 gi, xylose c chuyn ha chm hn v t hon ton. Mc d vic chuyn ixylose l kh ng kbi chng men ny, xylose vn khng c tiu thhon tonthm ch sau 30 gi. L tng nht, xylose nn c tiu thng thi [26] vi glucoseti mt hiu sut v tc tng ng, tuy nhin, ng len men ca cglucose vxylose em ha hn dn n t ph cng nghmi trong cng nghsn xut ethanollignocellulose.

Hcng pht hin ra rng ethanol l sn phm nhiu nht tvic chuyn haglucose &xylose, nhng mt lng nhcc sn phm phtqu trnh chuyn ha nhglycerol v xylitol cng c tm thy [28]. Chc chn, cc nghin cu sau ny sctp trung vo vic pht trin hoc ci tin cc chng hiu quhn, sn xut ethanol vichn lc v tc cao hn, v ti u qu trnh kthut.

4.5.3.6 Trch ly Ethanol trong qu trnh ln men

Mc d nhng nlc ng kdnh cho vic ln men ru, cc ng dng cngnghip btr hon do chi ph sn xut cao, m phthuc chyu vo nng lng uvo tinh chsn phm long cui cng, nng sut thp ca trng trt, v chi ph snxut enzyme cao. Nhng vn c lin quan trc tip n hin tng c ch.

Cng vi cc cng nghtruyn thng, trch ly lng-lng vi dung mi hu cthch ng sinh hc, chng ct chn khng, v hp thc chn lc trn cc cht rn chng minh tnh khthi kthut ca khi nim qu trnh ln men trch ly. Gn y, qutrnh tch bng mng lm gim skim chtnh thch ng sinh hc c xut. N

bao gm lc [85] v thm thu ngc [65]. Gn y, khi nim vmng cht lng htr

c bo co. Phng php ny gim thiu lng dung mi hu c tham gia v chophp thc hin ng thi cc giai on chit xut v phc hipha.

Nng cao nng sut v hiu sut chuyn ha c bo co [86] thng qua vicsdng mt tTeflon xp (ngm vi isotridecanol) htrcho vic chit tch ethanoltrong qu trnh ln men bn lin tc ca Saccharomyces bayanus. Qu trnh chn lc nydn n tinh chethanol v kt hp ba hot ng: ln men, chit tch, v ti chit tch


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nh biu thhnh 4.13. tng quy trnh mi c thtnghiu qusn xutru, titkim nng lng, v gim chi ph trong sn xut.

4.5.4 Chuyn ha ligninLignin c sn xut vi slng ln, khong 250 tpound mi nm ti Hoa K,

nh mt sn phm phca ngnh cng nghip giy v bt giy. Lignin l cc polymephc tp gc phenol v nh hnh m khng c ngun gc tng, do , hkhng thln men thnh ethanol. Lignin l mt polymer ngu nhin to thnh tcc gc propan

phenyl, ni gc phenol c thl mt guaiacyl hoc syringyl (Hnh 4.14).


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Cc gc ny lin kt vi nhau bng nhiu cch, phbin nht trong s l mi lin kt

ether hoc . Cc lin kt C-C cng hin din, nhng t gp hn (Hnh 4.15).


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Vic phn phi cc lin kt trong lignin l ngu nhin v qu trnh hnh thnh lignin lmt phn ng gc tdo m khng phi di skim sot enzym. Lignin cc kchngha cht, enzym, v thy phn vi sinh do lin kt ngang rng. V vy, lignin c thngc loi btip cn vi cellulose.

n vmonomer lignin tng tnh xng du, c chsoctan cao, do , bgycc phn tlignin thnh monome v loi boxy lm cho chng hu ch nh nhin liulng. Qu trnh chuyn ha lignin l xl bng hydro to ra hn hp phenolic vhydrocarbon, tip theo l phn ng vi methanol sn xut methyl aryl ether. Bc utin thng bao gm hai phn chnh: hydrodeoxygenation (loi oxy v nhm c cha xitcc vng phenol) v dealkylation (loi bcc nhm ethyl hoc chui ln trn ccvng). Vai tr chyu ca giai on ny l thc hin cc phn ng loi bccchui khng mong mundo khng cn thchin phn ng qu xa;iu ny sdn ntiu thqu mc ca hydro v to ra cc hydrocarbon bo ha, nhng HC ny khngtng chsoctane hiu qunh l cc hp cht thm. Hn na, tiu thqu nhiu hydrostng chi ph cho qu trnh chuyn ha. Cht xc tc thc hin cc phn ng c chc


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nng kp. Cc kim loi nh molypden v molypden / niken xc tc khoxy, v cht nnnhm axit thc y bgylin kt carbon-carbon.

Mc d ha cht lignin c ng dng trong bn khoan, nh cht kt dnh thc nchn nui, v nh l c scho vani nhn to, h khng c sdng trc nh b

mt dng thu hi du. Theo Naee [87], ha cht lignin c thc sdng theo haicchtrong ha cht tng cng thu hi du. Trong phng php mt, lignosulfonatesc pha trn vi cc amin mng vt v sulfonate du truyn thng to thnh mthn hp duy nht m chi ph t hn khong 40% khi sdng hacht chtdu mhocsn phm tdu m. Trong phng php thhai, lignin c phn ng vi hydro hoccarbon monoxide to thnh mt ha cht mi gi l phenol lignin. Bi v n c thho tan trong cc dung mi hu c, nhng khng phi trong nc, cc phenol ny l ngvin tt cho vic tng cng chuyn ha hn na sn xut ha cht c thhu chtrong tng cng thu hi du (EOR).

4.5.5 Cc sn phm khc trong cng nghEthanol Cellulosicgim chi ph sn xut ethanol tnguyn liu lignocellulose, cn thit phi m

rng hoc pht trin thtrng cho cc ng sn phm, cc sn phm ph, hoc cc dnxut. Coproducts tim nng bao gm hemicellulose thy phn (xylose), cellulose thy

phn (glucose ca cc hn hp ng), enzyme, lignin ha tan v khng ha tan, ligninc ngun gc tha cht v nhin liu, phthi rn... Sn phm c gi trkhc bao gmxylitol, m l mt cht lm ngt v c sn xut bng cch hydro ha xylose (mtaldehyde) thnh ru bc 1.

4.6 Cn bng nng lng cho sn xut ethanol tsinh khi (Biomass)Qu trnh pht trin sinh khi phthuc vo kinh tca qu trnh chuyn i, c

thl ha cht, enzyme, hoc kt hp ha cht v enzyme .Mt sc tnh c tnhton da trn cscng nghhin ti hoc tim nng.Mt yu tr rng l, bt kqutrnh no i na, svn chuyn ca vt liu sinh khi tngun ca n n v tr chuynha phi c gimc ti thiu.Khong 35% nng lng dkin sc tiu thbngcch vn chuyn cc cht khong 15 miles [68]. Chiph ng kca nng lng vn

chuyn nguyn liu ban u chra rng bt knh my chuyn i c phi c quy mtrung bnh v gn vi ngun sn xut nguyn liu ban u.

C mt ssphn i vi vic sn xut v sdng ethanol lm nhin liu.Quantrng nht l nhng li chtrch rng sn xut ethanol c thtiu thnhiu nng lnghn so vi ethanol cha ng. Cc nc Chu u phn tch rng vi vic sdng la mlm nguyn liu v bao gm c tnh nng lng lin quan n pht trin la m, vn


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chuyn n n nh my chng ct, lm ru, v vn chuyn n vo mt nh my lc dupha trn vi xng.Cc nc ny cho thy c li khi sdng cc sn phm chng hnkhi dng la m lm thc n cho gia sc stng ng vi sdng 5% ru thay thcho xng v tng ng vi nng lng thu c tvic chsoctane tng 1.25 im.

Nh gii thch y trong Chng 3, mt nh gi gn y v rt rng ritrn gi trnng lng rng (NEV) ca cng nghethanol tng [88] sdng cng nghxl tin tin cng nh dliu cng nghip thc thn [89,90] cho thy qu trnh snxut ethanol ng hin hnh Mto ra mt gi trnng lng rng tch cc ng k.ivi cellulose ethanol, mt syu tv cc vn bao gm sa dng nguyn liu vtnh sn sng, vic sdng cc loi cy trng khng phi thc phm, ti thiu hockhng sdng phn bn, khng sdng t canh tc, cng nghv qu trnh chuyn i

phc tp hn nhng vn ang pht trin a ra nh gi vn kh khn v cha c nhiu ngha thc tin.Tuy nhin nu chgii hn sdng nng lng sinh hc da vo quytrnh nng lng l sai lm. Da vo gi trca nhin liu sinh hc tcellulose v thmnh ca n , mt snh my nhin liu sinh hc tcellulose da trn cng nghxla dng ang hot ng hoc ang c xy dng trn ton thgii [91].

Nhu cu nng lng sn xut ethanol tcy trng khc nhau c nh gi biDa Silva v cng s. [92]. Giai on cng nghip lun lun c nhiu tn km nnglng, tiu tht60 n 75% tng nng lng. Nng lng chi tiu trong sn xut nngnghip bao gm tt ccc dng nng lng c sdng trong chbin nng sn vcng nghip, ngoi trnng lng mt tri m thc vt sdng cho stng trng. Giai

on cng nghip, bao gm ckhai thc v thy phn, qu trnh ln men ru, v chngct, cn khong 6,5 kg hi mi lt ru. N c thcung cp tng nhu cu nng lngcng nghip tsn phm phca mt sloi cy trng.V d, n cng l thng tin xem xt mt scn bng nng lng n gin ha, trong ch c nng lng nngnghip c thc hin nh l u vo v chc ethanol c ly lm u ra, b ma cungcp nng lng cho giai on cng nghip.

Hn na, dliu cng nghthng rt kh hoc gn nh khng thso snh giacc la chn khc nhau, do nhiu loi cy trng nguyn liu nh bt u t

lignocellulose. Do , BNng lng dn ti trca M chn thn cy ng l mhnh nguyn liu [93]. Sla chn ny da trn thc tl thn cy ng l ngun tinguyn sinh khi di do nht v tp trung Hoa Kv c thtn dng c shtngethanol ng , bao gm cthu hoch ng v sn xut ethanol [93].

Khng ging nh cc cng nghsn xut ethanol tcellulose, cng nghethanoltma l n gin hn v nh vy vic nh gi cn bng nng lng l tng i n


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gin. Kt qucn bng nng lng sn xut ethanol tcy ma Zimbabwe chrarng tlnng lng l 1,52 nu tt ccc u ra xem xt v 1.15 nu ethanol c coil u ra. Gi trbo co vtlnng lng thun sn xut ethanol tcy ma Brazil[92] l 2,41 v Louisiana, Hoa K[94], n l 1,85.Tlthp Zimbabwe l do (a) u

vo ln nng lng trong giai on nng nghip, pht sinh tnhu cu phn bn ln, v(b) tiu thnhin liu ha thch ln trong qu trnh chbin ma. Nh trong v dsosnh ny, kt qucn bng nng lng l phthuc vo mt slng ln cc yu tbaogm cng nghqu trnh chuyn i, cng nghnng nghip, kh hu v cht lng t,v nhiu hn na. NEV ca cellulose ethanol tcc phn tch bi Schmeretal. [95].Trong nghin cu ny, cy thn tho lu nm nh cswitchgrass c nh gi l loicy trng nng lng sinh hc tcellulose. Hai mi quan tm chnh ca cuc iu tra cahhiu qunng lng thc v tnh khthi kinh tca cv cc loi cy trng tngt.y l mt nghin cu c bn i din cho cc vt liu di truyn v cng nghnng

hc c sn sn xut chuyn i ctrong nm 2000 v 2001.Nghin cu ca hnhbo co sau.(a) . Sn lng sinh khi hng nm ca cc n vc bn trung bnh 5,2-11,1 Mg .vi trung bnh kt quc tnh sn lng nng lng rng (Ney) 60 GJ . .(b) Csn xut chuyn c 540% nng lng ti to so vi nng lng khng thtito c tiu th.(c). Qun l c canh ccho nng sut cao sn xut nng sut sinh khi hn 93% v ctnh tng n ca Ney cao hn c tnh trc y t cnhn to do u vo nngnghip thp.

(d) c tnh pht thi kh nh knh trung bnh tethanol cellulosic c ngun gc tcthp hn so vi c tnh lng pht thi kh nh knh txng 94%.

Ni chung, chi ph sn xut ethanol gim vi sgia tng nng lc ca cc c ssn xut,l im chung trong hu ht cc ngnh cng nghip ha du. Tuy nhin, tng chi ph tithiu tng ng vi mt im un, lc ny sgia tng trong chi ph sn xut cho mi giatng cng sut nh my c xem xt [42].Khnng ca stn ti ca mt mi quan hthc nghim gia quy m nh my hoc u ra v chi ph sn xut cng c kim tra

bng cch sdng chc nng sn xut khc nhau v cc gi trF tnh ton mc 5% c ngha [96]. N cng l tng tng rng nu khong cch trung bnh vn chuyn

nguyn liu v mua li trnn qu di do cng sut nh my tng ln, th chi ph sn xutc thbnh hng bi quy m nh my.

Ln men xylose c thc hin bi vi khun, nm, men bia, cc hthng menenzyme, hoc bin i gen vi sinh vt. Cng nghln men tin tin sgim chi ph 25%hoc nhiu hn trong trng hp ca cc vt liu loi thn tho, nh trong nghin cu


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ca Schmer et al. [95]. Nhng nlc ang c thc hin t c nng sut 100%v nng ethanol tng ln.Lignin l mt thnh phn chnh ca sinh khi, v chim hm lng nng lng ln can bi v n c mt nng lng cao hn nhiu so vi carbohydrate trn mi pound. Bi

v n l mt polymer phenolic n khng thc ln men ng, v thay v chuyn isang cc vt liu nh ete aryl metyl, cht tng thchvi xng v c sdng nh mtcht tng cng chsoctan cao. Skt hp ca cc qu trnh trn c tim nng snxut nhin liu vn ti mt mc gi cnh tranh.

4.7 Quy trnh Kinh tv hng chinlcMcAloon et al. [97] nghin cu chi ph sn xut ethanol tnguyn liu lignocellulose

so vi ttinh bt ng.Nh chra trong nghin cu ca h, so snh chi ph cthc hin gia cc ngnh cng nghip ethanol ng v cc ngnh cng nghip

lignocellulose-ethanol ang ni ln.Da trn gi cnh nm 2000, chi ph sn xutethanol nhin liu tcc qu trnh lignocellulose c xc nh l $ 1.50/gal, trong khi tqu trnh ng l $ 0.88/gal [97]. Khng cn phi ni, cc gi trchi ph xc nhnm 2000 khng thc coi l quy chun cho nm nay, do sthay i ng ktrongkhong thi gian ny dn n chi ph nguyn liu v c shtng liu cng nh chi phvn hnh khc nhau. pht trin thnh cng mt quy trnh cng nghlclignocellulosic cn phi gii quyt cc vn sau:

1. Ngun cung cp nguyn liu v phn phi hthng lignocellulose phi c thnhlp trn c skinh t. Chun bnguyn liu cng trthnh mt vn .

2.

Tng bc ca quy trnh cng nghcn c nghin cu ring cho cc ty chnkhc nhau v stng tc v kt ni gia cc bc phi c nh gi hon ton.Hiu ng tng tc gia cc giai on trnn rt quan trng, bi v sn phm camt giai on v cc sn phm c thhot ng nh cc cht c chgiai on tiptheo.

3. Mt c sdliu ton din cho mt lot cc nguyn liu khc nhau phi cthit lp. Mt nguyn liu khc nhau c thc chn lm nguyn liu m hnhcho cc quc gia v khu vc khc nhau , ty thuc vo ssn c ca a phng,hn chhu cn, v li ch c shtng. Hn na, cng nghchuyn i nn ddng thch nghi vi nguyn liu v nng nghip d lignocellulose khc [93].

4. Quy m ln l ht sc quan trng i vi hot ng thng mi cng nh gim thiu ri ro lin quan trong nlc mrng sn xut. Ngoi ra, mt hot ngtrn quy m ln sgip chng minh phn tch vng i mi trng m kt qulc ngha hn.


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5. Chi ph thp nhng hiu qucao cho cc enzyme cng nghphi c pht tringim chi ph hot ng v nng cao nng sut. Nhng nlc hin ti ca Phngth nghim quc gia nng lng ti to, Genencor quc t, v Novozymes Cngnghsinh hc l rt quan trng v ng ch trong vn ny. Tin bhn na

slm cho vic thng mi ha fullscale ethanol cellulosic gn hn v nhiu hnna khthi vmt kinh t.

ethanol từ lignocellulose

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