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journa l homepage: www.e1. Introduction

The textile industry is one of Taiwans main industriescontributing 20 billion US dollars to the economy in 2007. Althoughthe dyeing process is a key step in increasing the value of the textileindustry, it produces large quantities of toxic, low biodegradable,highly colored wastewater. Without suitable treatment, suchwastewater would destroy the natural water environment (Banatet al., 1996; Pierce et al., 2003; Robinson et al., 2003). The azo-dyes,including reactive, acid, and direct dyes, are commonly used in thetextile industry (Vijayaraghavan and Yun, 2007). Among these azodyes, the reactive azo dyes contain one to four azo bonds (N N) andare used to dye cellulose bers, wool and nylon by forming covalentbonds with the bers (Khare and Bose, 2007).

Various types of wastewater treatment processes that can beused to treat the dye containing wastewater, include physical (e.g.,coagulation, activated carbon adsorption, ion exchange, ROmembrane ltration), chemical oxidation (e.g., UV/O3, UV/H2O2,fenton reagent), advanced oxidation processes (e.g., photocatalysis,electrochemical, sonolysis, ionizing radiation) as well as biological

(e.g., activated sludge, SBR) (Hai et al., 2007). Biodegradation by thetraditional aerobic/anaerobic activated sludge or aerobic biolmprocesses are most commonly applied worldwide due to itssimplicity and low cost treatment. However, the low biodegrad-ability under aerobic conditions limits the application of aerobicbiological process for the treatment of dye containing wastewater.Another problem is the longer hydraulic retention time or largeraerobic tank is needed (Khare and Bose, 2007). Although theanaerobic degradation performance of dye containing wastewaterby the anaerobic biological process is quite good, the metabolites,include aromatic amine, is more toxic than the dye itself. Thus, atwo-stage biological process, with both anaerobic and aerobicreactors congured in sequence must be used to treat wastewatercontaining reactive dye (Libra et al., 2004).

The anaerobic activated sludge unit is always the rst stage ofthe two-stage biological process. During the anaerobic stage, theazo bonds of the reactive dye are degraded, resulting in a reductionof the color and the production of toxic colorless aromatic amines.In the following aerobic activated sludge unit, these colorlessaromatic amines are then further degraded/mineralized to themeet of efuent discharge standard criteria (Libra et al., 2004).

In this study, a two-stage biological bioreactor was successfullyutilized to treat Reactive Black 5 (RB5) containing syntheticwastewater tomeet the Taiwan EPA efuent criteria. The anaerobiccolor degrading bacteria were further isolated and compared bytradition culturing method in this study.

Azo dye degradation

Reactive Black 5

Lactococcus lactis

Lactobacillus casei

more than 99% of the RB5 within 5.5 h. Twenty types of medium RB5 degrading isolation were observed

to be different subspecies of Lactobacillus casei, which could degrade more than 99% of the RB5 within

36 h. Finally, the experiments also showed that the RB5 degradation performance of the L. casei was

improved by the suitable addition of carbon and nitrogen source in the medium.

2009 Taiwan Institute of Chemical Engineers. Published by Elsevier B.V. All rights reserved.

* Corresponding author. Tel.: +886 3 2654911; fax: +886 3 2654911.

E-mail addresses: sjyou@cycu.edu.tw (S.-J. You),

nickprometheus@yahoo.com.tw (J.-Y. Teng).1 Tel.: +886 3 2654911; fax: +886 3 2654911.

1876-1070/$ see front matter 2009 Taiwan Institute of Chemical Engineers. Published by Elsevier B.V. All rights reserved.doi:10.1016/j.jtice.2009.01.007Anaerobic decolorization bacteria for thanaerobic and aerobic membrane biorea

Sheng-Jie You a,*, Jun-Yu Teng b,1

aDepartment of Bioenvironmental Engineering and R&D Center for Membrane TechnolobDepartment of Civil Engineering, Chung Yuan Christian University, Chungli 320, Taiwan

A R T I C L E I N F O

Article history:

Received 15 November 2008

Received in revised form 8 January 2009

Accepted 31 January 2009

Keywords:

Decolorizing bacteria

A B S T R A C T

Textile dyeing wastewater

on the treatment of waste

sequencing batch reactor (

addition the anaerobic RB5

tested separately. Nearly 9

achieved using the anaerob

bacteria isolated were sequtreatment of azo dye in a sequentialtor

Chung Yuan Christian University, Chungli 320, Taiwan

harmful to both marine organisms and human beings. This study focused

ater containing an azo dye, Reactive Black 5 (RB5), using an anaerobic

R) combined with an aerobic membrane bioreactor (aerobic MBR). In

egrading bacteria were isolated and their individual performance were

and 5.2% of COD removal and 74.6 and 9.1% of true color removal was

SBR and the aerobic MBR respectively. Five types of high RB5 degrading

ced to be different subspecies of Lactococcus lactis, which could degrade

te of Chemical Engineers

l sev ier .com/ locate / j t i ce

gram

S.-J. You, J.-Y. Teng / Journal of the Taiwan Institute of Chemical Engineers 40 (2009) 500504 5012. Materials and methods

2.1. Process conguration

Fig. 1 shows schematic diagrams of the AOMBR (anaerobicsequencing batch reactor plus Oxic Membrane BioReactor) processwhich includes a 36 L anaerobic SBR and an 18 L aerobic MBR unitoperated under laboratory conditions at 20 8C. The lling, reaction,settling and drawing times in the anaerobic SBR unitwere 0.5, 21.5,0.5 and 1.5 h, respectively, and no anaerobic sludge was discardedas waste during the operating period. The HRT, MLSS, and ORP ofthe anaerobic SBR were 48 h; 2700 mg/L; and 300 mV, respec-tively. In the following aerobic MBR unit, the efuent from themembrane process was drained by a peristaltic pump thatoperated in alternate cycles of 10 min on followed by 5 min off.A at sheet-shaped membrane module made of polytetrauor-oethylene (PTFE) with a pore size of 0.22mm was used in MBRwhich was produced by the R&D Center for Membrane Technologyof Chung Yuan Christian University, Taiwan. The HRT, MLSS, andORP in the aerobic MBR were 24 h, 2100 mg/L, and higher than250 mV, respectively. The seed sludge was taken from the Kuagninindustrial park wastewater treatment plant. 38.2% of the totalwastewater efuent from this plant consists of highly coloredtextile dyeing wastewater.

2.2. Wastewater and analytical methods

After seeding with the activated sludge from the Kuagninindustrial park wastewater treatment plant, synthetic wastewaterwas then fed into the AOMBR reactor. The substrate used for thereactor cultivation contained (per liter): milk powder, 177.1 mg;sucrose, 17.7 mg; acetate, 32.6 mg; (NH4)2SO4, 12.5 mg; urea,39.1 mg; FeCl3, 0.13 mg, KH2PO4, 17.7 mg, and RB5, 6.25 mg. Giventhese constituents, the concentrations of COD, BOD, SS, and true

Fig. 1. Schematic diacolor (unit in ADMI) were 300 mg COD/L, 200 mg BOD/L, 200mg SS/L, and 1000 ADMI, respectively, simulating concentrationsin inuent wastewater from the Kuagnin industrial park waste-water treatment plant. All the processesweremonitored 23 timesperweek. All the samples taken from the reactorswere rst lteredrapidly using Whatman GF/A lter paper, then analyzed to ndtheir true color, COD, BOD, and SS according to the Standardmethods for the examination of water and wastewater (APHA,1989).

2.3. Isolation of the anaerobic color degrading bacteria

The culturing method was used to isolate the anaerobic colordegrading bacteria. Sludge taken from the anaerobic SBR unit wascultured and isolated in a TGC agar medium (Thioglycollatemedium, Difco) at 37 8C for 48 h in an anaerobic oven. Sixtyseparate colonies were transferred from the medium to a TGCbroth medium for culturing at 37 8C for 48 h in an anaerobic oven.Two different experiments were then performed on these sixtyisolated samples.

2.4. Color removal rate testing for all isolates

The sixty isolates were further tested after 36 h to determinethe degradation rate of the anaerobic color in the TGC brothcontaining 50 mg/L of RB5. The degradation rate calculation wasbased on the difference of OD595 at 0 h and after 6/36 hdegradation. Three types of isolates (i.e., high-, medium- andlow-color degrading bacteria)were screened in this test. In order toreduce the interference of OD595 and OD600, 1 mL samples werecentrifuged at 3000 rpm for 3 min. The supernatant werediscarded to another tube to measure the absorbance at595 nm. On the other hand, the pellets were then resuspendedto 1 mL by added ddH2O and repeated centrifuge-resuspend foranother two times. The resuspend samples were then measuredthe absorbance at 600 nm. In addition, each data shown in Section3 were analyzed and averaged by three different batch experi-ments. The DNA of the high/medium anaerobic color degradingbacteria was further extracted, sequenced and compared with theNCBI database.

2.5. Testing for color degradation ability without the addition of

nitrogen/carbon sources

In order to conrm whether the color degrading bacteria canperform RB5 degrading by the nitrogen/carbon of the dye or not,this study further using nitrogen lacked mineral salt medium(MSM) in broth to culture the isolates anaerobically. This MSMmedium contained (per liter): Na2HPO47H2O, 6.7 mg; KH2PO4,1.0 mg; MgSO47H2O, 0.2 mg; FeCl3, 0.06 mg; CaCl22H2O, 0.1 mg;

of AOMBR process.RB5, 6.25 mg; and trace element solution, 1 mL. The trace elementsolution contained (per liter): H3BO3, 0.3 mg; CoCl2, 0.2 mg;ZnSO47H2O, 0.1 mg; MnCl24H2O, 0.03 mg; Na2MoO4, 0.03 mg;NiCl26H2O, 0.02 mg; and CuSO45H2O, 0.01 mg. The color degra-dation rate was determined by testing the isolates after 8 days ofanaerobic growth in the MSM broth containing 50 mg/L of RB5without the addition of external carbon or nitrogen.

3. Results and discussion

3.1. Performance of the AOMBR process

Fig. 2(a) and (b) shows the results for the COD removal and truecolor removal pattern at each stage respectively of the AOMBRprocess. It was observed in Fig. 2(a) that the average CODs forinuent (total), anaerobic SBR efuent (soluble), and aerobic MBR

al performance for the AOMBR process.

S.-J. You, J.-Y. Teng / Journal of the Taiwan Institute of Chemical Engineers 40 (2009) 500504502efuent (soluble) were 310.6 31.7, 23.8 8.4 and 7.9 2.3 mg/L,respectively, which corresponds to cumulative COD removal ef-ciencies of 92.3 and 97.5% for the anaerobic SBR and aerobic MBR,respectively. In addition, Fig. 2(b) shows results for the true color afterthe AOMBR process. The average true color of the inuent, anaerobicSBR efuent and aerobic MBR efuent are 1039.1 153.4,264.2 49.9, and 169.0 22.4 ADMI, respectively, which corre-sponds to accumulated removal efciencies of 74.6 and 83.7% for theanaerobic SBR and aerobicMBR, respectively. In other words 92.3 and74.6% of the COD and true color were removed in the anaerobic SBR,showed an excellent performance. On the other hand, the COD andtrue color removal efciency of the aerobic MBR was only 5.2 and9.1%, respectively. Isik and Sponza (2008) have operated a sequentialanaerobic/aerobic reactor system to treat azo dyes containing textilewastewater and they observed the COD and color removal efciencieswere between 84 and 97%, which are close to this study. Libra et al.(2004) also studied a two-stage anaerobic/aerobic process to removeReactive Black 5 and they found an overall color removal of about 65%,which was lower than present study.

It was also observed that due to formation of intermediate themaximum absorbance shifted from 595 to 265 nm after anaerobictreatment of Reactive Black 5 containing wastewater, which wasalso observed by Mohanty et al. (2006). The predominantintermediate metabolite was further analyzed as amine com-pounds in Mohantys study. In this study, the OD265 of theanaerobic SBR efuent was 0.850, which was further reduced to0.321 in the aerobic MBR efuent. This indicated that nearly 62.3%of the toxic amine compounds was degraded in the aerobic MBR.Delee et al. (1998) also stated that 6295 and 60% of the color andCOD removal can be achieved by anaerobic treatment, while anadditional 30% of the COD, which are mostly contributed byaromatic amines, can be removed by the subsequent aerobic

Fig. 2. (a) COD and (b) true color removtreatment. Thus, although the COD and ADMI removal efcienciesof the aerobicMBRwere not high, the aerobic stagemust be used inorder tomineralize the amines into non-toxicmetabolites (Isik andSponza, 2008; Libra et al., 2004) and to retain the particulatematterin the reactor.

3.2. Color removal rate testing for all isolates

Three types (i.e. high, medium and low) color degradingbacteria were isolated from the anaerobic SBR by using a TGCmedium. Screening studies identied ve high color degradingisolates, which could degrademore than 99% of the RB5within 6 h,twenty medium color degrading isolates, which could degrademore than 99% of the RB5within 636 h, and twenty-ve low-colordegrading isolates, which could degrade more than 70% of the RB5within 636 h. Also ten isolates were identied, which do notcontribute to the color removal. In this section, we discuss only theexperimental results for the high and medium color degradingisolates.

3.3. High color degrading isolates

The RB5 degradation performance (OD595, the characteristicwavelength of RB5) and cell growth (OD600) of the ve high colordegrading bacteria (numbered AN-13, AN-20, AN-23, AN-27 andAN-51) are illustrated in Fig. 3. It was observed that thedegradation performance and cell growth pattern of all veisolates was similar. The RB5 was degraded rapidly without cellgrowth in the rst 2 h.

It was also observed that on average, more than 70% of the RB5was degraded during the rst 2.5 h, and over 95 and 99%was degraded during the rst 4.5 and 5.5 h, respectively. Inaddition, the RB5 degradation rate was higher in the rst 2.5 h(0.48 OD595/h = 14.55 mg dye/L h), than the following 3 h (0.10OD595/h = 3.21 mgdye/L h). On the other hand, no cell growthwasobserved in the rst 2 h. The average cell growth rate was 0.508OD600/h from2 to 3.5 h and 0.042OD600/h in the following 2 h. Theaverage specic RB5 degradation rate for the rst 2 h wasobserved to be much higher (553.35 mg dye/OD600 L h) than thatfor the following 3.5 h (6.68 mg dye/OD600 L h). This signicantdifference was due to no cell growth observed during the rst 2 h.This suggests that the high RB5 degrading bacteria could cleavethe azo bondswith a very short lag phase. On the other hand, therewas a signicant decrease in the average pH of the medium (from7.0 to 4.25) during experimental period (5.5 h), which indicatesformation of some acidic compounds during degradation.

The ve high RB5 degrading bacteria were further sequencedusing the 16S rRNA gene and the results compared with the NCBIFig. 3. Color removal performance by the 5 high degradation performance isolates.Item D indicates the RB5 degradation curve and G indicates the bacterial growth

curve.

Table 1Phylogenetic relationship of the high/medium RB5 degrading isolates.

Isolates no. Phylogenetic relationship

Species Source

High RB5 degrading isolates

AN-13 Lactococcus lactis subsp. lactis DQ171

AN-20 Lactococcus lactis subsp. lactis AB2851

AN-23 Lactococcus lactis subsp. lactis AB2851

AN-27 Lactococcus lactis AY6752

AN-51 Lactococcus lactis subsp. lactis DQ171

Medium RB5 degrading isolates

AN2 Lactobacillus casei DQ462

AN3 Lactobacillus casei DQ462

AN4 Lactobacillus sp. B5406 AB0706

AN26 Lactobacillus casei DQ462

AN32 Lactobacillus casei DQ462

AN37 Lactobacillus casei DQ462

462

S.-J. You, J.-Y. Teng / Journal of the Taiwan Institute of Chemical Engineers 40 (2009) 500504 503database (see Table 1). All the high RB5 degrading bacteria weresubspecies of Lactococcus lactis, a kind of non-moving Grampositive coccus without spores or agellum. The L. lactis bacteriaproduce lactic acid by the fermentation of lactose, which leads to adecrease in the pH. It is also reported that the cell growth for L.lactis will not occur at pH below 4.4 (Kim et al., 1999). A similarresult was also observed in this study. None of the 5 high dye-degrading bacteria grew after 3.5 hwhen the pH decreased to 4.25;see Fig. 3. A comparison of the 16S rRNA sequences of these veisolates showed 9698% of similarities between them, thereforethey can be considered to be the same species. In only one study ondye degradation by L. lactis (Learoyd et al., 1992) have found thatthe dye reduction of L. lactiswas enhanced by sugar rather than byorganic acids.

3.4. Medium color degrading isolates

Nearly twenty medium color degrading bacteria, which coulddegrade more than 99% of the RB5 with 636 h, was isolated.However, only seven of these isolateswere sequenced successfully.Fig. 4 shows the color removal performance of these sevenmediumcolor degrading isolates. It was observed that 44.1% of the RB5 wasdegraded during the rst 3 h, and on an average of 58.75, 71.54 and96.5% removal efciency during the rst 6, 12 and 36 h,respectively. The average RB5 degradation rates during the 3, 6,12 and 36 hwere 6.64, 4.49, 2,84 and 1.25 mg dye/L h, respectively.There was no cell growth observed during the rst 4 h. The averagecell growth rate was 0.052 OD /h from 4 to 20 h and 0.003

AN49 Lactobacillus casei DQ600

OD600/h in the following 10 h. The average specic RB5 degrada-tion rate for the rst 4 hwas observed to bemuch higher (26.58 mg

Fig. 4. Color removal performance of the sevenmediumdegradation isolates. ItemDindicates the RB5 degradation curve and G indicates the bacterial growth curve.dye/OD600 L h) than that for the following 16 h (0.096 mg dye/OD600 L h). This signicant difference was due to no cell growthduring the rst 4 h, similar to the cell growth trend shown by thehigh RB5 degrading bacteria. This also suggests that the mediumRB5 degrading bacteria could cleave the azo bonds with a veryshort lag phase. There was also a signicantly decrease in theaverage pH (from 7.0 to 4.38) within the rst 20 h of theexperimental period, which indicates that these 7 isolatesproduced acidic compounds during dye/medium degradation.

The 16S rRNA genes of the seven medium RB5 degradingbacteria were further sequenced and the results compared withthe NCBI database, as shown in Table 1. All the medium RB5degrading bacteria were identied to be genus of Lactobacillus;most were the species of Lactobacillus casei. The L. casei is also akind of Gram positive bacteria, producing lactic acid by thefermentation of lactose (Axelsson, 1998), which in turn leads toa decrease in the pH, just like the L. lactis of the high RB5degrading bacteria. A comparison of the 16S rRNA sequences ofthese seven isolates also shows that they share 9799% ofsimilarities of between them. Therefore they can be consideredto be the same species. The L. casei have also shown good dyedegradation performance for non-azo dyes (Seesuriyachan et al.,2007).

Two lacto bacteria (i.e., L. lactis and L. casei) with high andmedium RB5 degradation performance, were identied as thepredominant dye-degrading anaerobic bacteria. However, in otherstudies, Bacillus subtilis, Pseudomonas spp., Geobacillus strarother-mophilus, Rhodobacter sphearoides and Enterococcus faecalis

in NCBI Percentage of similarity Match bps.

718.1 97% 1149/1181

24.1 81% 334/409

24.1 97% 1154/1184

42.1 98% 1179/1201

718.1 97% 1156/1190

440 97% 1159/1185

440 98% 1160/1178

09 98% 1132/1148

440 98% 945/959

440 99% 1155/1175

440 98% 1145/1164

440 98% 1137/1154showed high azo dye reduction ability, which was not the casein our study (Chang et al., 2001).

3.5. Effect of nitrogen/carbon on color degradation performance of

bacteria

In the above experiments, screening showed the two majorcolor degrading lacto bacteria having high or medium RB5degrading performance. However, it was not clear whether thesetwo isolates could degrade RB5 with simply the nitrogen/carboncontained in the RB5 itself. Thus, further experiments wereperformed using an MSM medium that lacked nitrogen instead ofthe TGC medium; see Fig. 5. Two isolates (i.e., AN13 for high- andAN37 formedium-RB5 degrading bacteria) were used in this study.As already described above, with TGC medium, both AN13 andAN37 showed rapid degradation performance within 1 day. Incontrast, degradation of RB5 was very slow (for both AN13 (0.112OD595/h) and AN37 (0.129 OD595/h)) when the nitrogen-lackingMSM medium was used. However, after the addition of the TGC

medium on 3rd day, therewas a rapid decrease in RB5 observed forAN37 from day 3 to day 5. The degradation rate for AN13 and AN37from day 3 to day 5 was 0.154 OD595/h and 0.360 OD595/hrespectively. This indicates that the external carbon or nitrogenaddition had a signicant effect on the degradation performance of

Acknowledgements

This study was supported by a grant received from the NationalScience Council (No. NSC 96-2621-Z-033-002-MY3) and theCenter-of-Excellence Program on Membrane Technology/Ministryof Education, Taiwan, Republic of China.

References

APHA. Standard Methods for the Examination of Water and Wastewater, 17th Ed.,American Public Health Association, Washington, DC, USA (1989).

Axelsson, L., Lactic Acid Bacteria: Classication and Physiology, Salminen, S. & A. VonWright (Eds.), Marcel Dekker, Inc., New York, USA (1998).

Banat, I. M., P. Nigam, D. Singh, and R. Marchant, Microbial Decolorization of TextileDye Containing Efuents: A Review, Bioresour. Technol., 58, 217 (1996).

Chang, J. S., C. Chou, Y. C. Lin, P. J. Lin, J. Y. Ho, and T. L. Hu, Kinetic Characteristics ofBacterial Azo-Dye Decolorization by Pseudomonas luteola, Water Res., 35, 2841(2001).

Delee, W., C. ONeill, F. R. Hawkes, and H. M. Pinheiro, Anaerobic Treatment of TextileEfuents: A Review, J. Chem. Technol. Biotechnol., 73, 323 (1998).

Hai, F. I., K. Yamamoto, and K. Fukushi, Hybrid Treatment Systems for DyeWastewater, Crit. Rev. Environ. Sci. Technol., 37, 315 (2007).

Isik, M. and D. T. Sponza, Anaerobic/Aerobic Treatment of a Simulated TextileWastewater, Sep. Purif. Technol., 60, 64 (2008).

Khare, U. K., P. Bose, and P. S. Vankar, Impact of Ozonation on Subsequent Treatmentof Azo Dye Solution, J. Chem. Technol. Biotechnol., 82, 1012 (2007).

Kim, W. S., J. N. Ren, and W. Dunn, Differentiation of Lactococcus lactis SubspeciesLactis and Subspecies Cremoris Strains by Their Adaptive Response to Stresses,FEMS Microbiol. Lett., 171, 57 (1999).

Fig. 5. RB5 degradation with/without additional carbon/nitrogen.

S.-J. You, J.-Y. Teng / Journal of the Taiwan Institute of Chemical Engineers 40 (2009) 500504504AN37 (L. casei), but not AN13 (L. lactis).

4. Conclusion

In this study wastewater containing the azo dye-RB5 wastreated effectively using combination of an anaerobic SBR followedby an aerobic membrane bioreactor. The process showed excellentCOD and true color removal performance in the anaerobic SBR. Thebacteria screening studies showed nearly 5 types of high, 20 typesof medium and 25 types of low RB5 degrading bacteria werepresent in anaerobic SBR reactor. All the high RB5 degradingisolates were further sequenced and found to be differentsubspecies of L. lactis, where as all the medium RB5 degradingisolateswere found to be different subspecies of L. casei. Finally, theRB5 degrading performance of L. casei was improved with theaddition of suitable amounts of carbon and nitrogen.Learoyd, S. A., R. G. Kroll, and C. F. Thurston, An Investigation of Dye Reduction byFood-Borne Bacteria, J. Appl. Bacteriol., 72, 479 (1992).

Libra, J. A., M. Borchert, L. Vigelahn, and T. Storm, Two Stage Biological Treatment of aDiazo Reactive Textile Dye and the Fate of the Dye Metabolites, Chemosphere, 56,167 (2004).

Mohanty, S., N. Dafale, and N. N. Rao, Microbial Decolorization of Reactive Black-5 in aTwo-Stage Anaerobic-Aerobic Reactor Using Acclimatized Activated TextileSludge, Biodegradation, 17, 403 (2006).

Pierce, C. I., J. R. Lloyd, and J. T. Guthrie, The Removal of Colour from TextileWastewater UsingWhole Bacterial Cells: A Review, Dyes Pigments, 58, 179 (2003).

Robinson, T., G. Mcmullan, R. Marchant, and P. Nigam, Remediation of Dyes in TextileEfuent: A Critical Review on Current Treatment Technologies with a ProposedAlternative, Bioresour. Technol., 77, 247 (2003).

Seesuriyachan, P., S. Takenaka, A. Kuntiya, S. Klayraung, S. Murakmi, and K. Aoki,Metabolism of Azo Dyes by Lactobacillus casei TISTR 1500 and Effects of VariousFactors on Decolorization, Water. Res., 41, 985 (2007).

Vijayaraghavan, K. and Y. S. Yun, Utilization of FermentationWaste (Corynebacteriumglutamicum) for Biosorption of Reactive Black 5 from Aqueous Solution, J. Hazard.Mater., 141, 45 (2007).

Anaerobic decolorization bacteria for the treatment of azo dye in a sequential anaerobic and aerobic membrane bioreactorIntroductionMaterials and methodsProcess configurationWastewater and analytical methodsIsolation of the anaerobic color degrading bacteriaColor removal rate testing for all isolatesTesting for color degradation ability without the addition of nitrogen/carbon sources

Results and discussionPerformance of the AOMBR processColor removal rate testing for all isolatesHigh color degrading isolatesMedium color degrading isolatesEffect of nitrogen/carbon on color degradation performance of bacteria

ConclusionAcknowledgementsReferences