Polluticn Preventiun and Waste Minhizatian in the Dairy Industry through Novel Uses of Whey Pe-te

Sbang-Tian Yang

Departnrent of Chemical mgineering The O h i o State University

Columbus, O h i o 43210

Whey is produced during the manufacture of cheese and casein, About 28 billion pounds of liquid whey produced in the U . S . are being durped into nnmicipal sewers, causing serious pollution problems. While whey protein is recovered by ultrafiltration, the renraining whey permeate represents a mjor disposal problem for the dairy industry. The utilization of whey pemreate as a fermentation feedstock for chemical production will generate usable and valuable products while reducing waste pollution problem. However, there is not a single, universal solution in the dairy industry for the whey disposal problems. This is due t o the large variations in quantities and properties of

the liquid whey produced at different plants. This paper identifies several potential fermentation products fran whey permeate and discuss consideratiam in selecting a whey fermentation process.

Prepared for presentation at the AI- Pollution Prevention Conference Washington, D.C., Decder 4-5, 1989.

3

Current Uses of Cheese Whey and Its C” nents

Depending on the cheese-makhg process, there are two principle types of whey: sweet whey and acid whey. Acid whey, from cottage and cream cheeses manufacturing, comprises only about one sixth of the total whey production. Table 1 shms the characteristics and campositions of typical sweet whey and acid whey. Liquid whey can be concentrated, dried, and used as animal feed or food ingredient, or can be converted to chemicals, fuels, and many other valuable products. Figure 3 shuws some processes and products associated with whey utilization/disposal.

Table 1. Characteristics and Compositions of Cheese Whey

Sweet Whey Acid Whey Components (%I Fluid Dried Fluid Dried Total Solids 6.35 96.5 6.5 96.0 Moisture 93.7 3.5 93.5 4.0

4.85 75.0 4.90 67.4 Lactose Protein 0.8 13.4 0.75 12.5

Fat 0.5 0.8 0.04 0.6 Lactic Acid 0.05 0.2 0.4 4.2 Ash 0.5 7.3 0.8 11.8

DH 5.5-6.0 4.0-4.5

Dried Whey m e r Most of whey and modified whey proctucts are made from sweet whey. The

largest use of whey is the dried whey mer as a food ingredient or animal feed (Figure 4). However, the conversion of sweet whey into a food-grade ingredient or m - h l feed by evaporation and drying is energy intensive and is only econdcal for large plants. The market for dry whey powder is also saturated and very competitive. Small to medium-size plants (less than 10 million Ibs annually) cannot justify costs for producing dried whey powder. Also, only 8.2% of the total acid whey generated in the U.S. becomes a marketable product. For these cheese plants, whey is usually disposed of by either landspreading or discharging hto a municipal waste treatment system.

4

3, WHEY PROCESSING DlsPosaI > LanQwead

6000 Ibs 15% T. S.

Cheese

100.000 Ibs Process MILK _j Making >WHEY

90.000 Ibs *

M Y PEFWE-

ATE

84.oca In

V CHEESE 1O.OOO Ibs

> LF

4 Xanthan

* sewers

j w h e y Drirh

3 Pasteuizattm > whey Cream

4 w h e y S Y W

__j Died whey

> Carmtrattm > w P c

_j Lactose

cj Methane

j SCP > Fermentaticn

Figure 3. Fmducts f m Whey Processing.

Production of Whey Products ‘So/id Content in Mi//ion Pounds

Whey Powder 62.7%

Mod. Dry whey Lactose 6.7% 6.1% 7.8%

1 9 8 5

Figure 4. Whey and M d f i e d Whey Prcducts.

5

Whey Proteins Recovery of whey proteins, which make up 15% to 22% of the total milk

proteins, by ultrafiltration has become a common operation for large dairy plants. Whey protein concentrate (WFC) recovered by ultrafiltration contains 68.4% p-lactoglobulin, 21.3% a-lactoglobulin, and 10.3% serum proteins, and is a valuable product because of its excellent functional properties and nutritional values. However, the remaining lactose stream (whey permeate) becames a mjor disposal problem.

Lactose The major waste problem in the dairy industry is the disposal of whey

permeate. The challenge is to identify suitable processes to utilize lactose in permeate for maxi" econdc return. Lactose, which amounts for 70%-80% total whey solids, can be readily isolated and purified from permeate by crystallization (Zadow, 1984). However, this process is not attractive because the present world mrket for lactose is limited and very competitive. Furthermore, the lactose recovery yield f m whey permeate is low (only about 60%) and the waste stream (mother liquor) from this process contains high salts (>20%), high lactose (-20%) and high BOD. Because of the high salt content, this mother liquor is unsuitable for any use and requires costly waste treatment. Fi&e 5 shuws a typical dairy plant producing whey protein concentrate ( W X ) and lactose as two major byproducts. The weak marketing potential for lactose and the increasing waste treatment costs have necessitate3 the search for alternative uses of whey permeate.

Modified Whey products Several modified whey products, including partially demineralized and

delactosed whey, are used in human foods and animal feed. But the quantities are small. Whey lactose can be hydrolyzed by an enzymatic process and then used to produce whey syrup or other products. Whey lactose also can be chemically converted to other useful products such as polyurethane and adhesive resins. Several whey drinks, including alcoholic and non-alcoholic beverages, also have been researched. But none of these products were quite successful, cmm-ercially. The major problems in developing these new products f m whey are two-fold: 1) to campete with the existing products in the market is difficult; 2) to develop the market for new products is costly.

6

Pffmt- ate - - - - - -

WHEY > UF > RO 3 > 100.000 Ibs

7% T.S 5% Lactose 1% Rotein EVAPORnTOR CRYSTALIZER

Water DE” WPC

Lactow.

Washing <

TO WASTE

DISPOSAL Mot her - - - -*- Liquor

T- SPRAY

Lactose 3000 Ibs

45% T S 20% Lnctose

Figure 5. A Process for proauctions of WPC and Lactose fram Whey.

Fermentation of Whey Permeate

In addition to enzymatic and chemical modifications of lactose, whey fennentation is the most studied subject in the dairy industry for alternative use/disposal of whey permeate. The utilization of whey lactose as a fermentation feedstock has been of great interest to the dairy industry ( H o h a n , 1984). Table 2 shows that a wide range of products can be obtained from whey fermentation, including single cell protein, methane, ethanol, lactic acid, butanol, citric acid, ax3 biopolyrrers. Many other biochemicals can be added to this list. However, selection of a suitable fennentation process nust take into account technological, market, and econOmic factors.

7

1 Table 2. Sane Fermentation Products from Whey and Whey Permeate.

Product Microorganism Note/Reference

Single Cell Proteins Mold Y e a s t s

A1 coho1 s Ethanol

2,3-But~ediol Butanol Glycerol

Orqanic Acids Lactic Acid

Citric Acid Butyric Acid Propionic Acid

Acetic Acid

Pol Ysaccharides Xanthan Gun

Methylpentose-Glu-Gal L i p i d s ( O i l )

Oleic, Linoleic Acids

Enzvmes 6 -Galactosidase

Bacterial Insecticides Spore-6-endotoxin

F1 avor C m o u n d s

Diacetyl

Vitamin B

Cor r inoi ds

Penici 1 1 im cycl opium Kl uvermyces f ragi I is Saccharanyces cereviciae

Anaerobic digestion

Kl uvermyces f ragi 1 is Zyman0na.s mobilis Bad 1 1 us pol ymyxa CI os t ridim acet obu tyl i cum Yeasts

Lactobacillus bulgaricus Lactobacil lus helveticus Aspergi 1 1 us niger Clostridim bei jerinckii Propionibact e r i m acidi - Acetobacter spp.(ethanol) Streptococcus lactisl cl os t ridim f o m i coacet i c~on

propi oni c i

Xanthunonas canpestris

Propionibacteria

Api o t ri chum curva t um candida curvata

Candida pseudo t ropi cal is

&ci I i us thuringiensis

Heurty, S.A. France Amber Labs. Juneau, WI Corning/Kroger,

Foremost Dairies, Inc, CA

Abcor., MA, Dale (1985) Rajagoplan & Kosikowski S p e c h 6 Collins (1982) Ennis (1986), Park (1989)

Meharia i5 Cheryan (1987) Roy e t a1 (1987) Maddox (1983) Alam et a1 (1988)

Blanc & Gana (1987) Kraft, IL Tang e t a1 (1988)

Charles & Radjai (1977) Schwartz & Bodie (1986) Crow (1988)

Ykema e t a1 (1988) F1 oetenmeyer (1985)

Game2 e t a1 (1983)

Salana et a1 (1983)

Streptococcus diacetylactis Troller (1981)

\ Propionibacteriun shenranii Marwaha et a1 (1983) /

Propi onibact eri m Janicka et a1 (1976)

8

Single cell proteins (SCP) have been produced from whey and whey permeate. The major obstacle for this application is the limited xnarket for the product. SCP is not attractive t o human consumption due t o the inherent esthetic problems and health concerns; it is not cmpetitive in the animal feed market either, due t o the relatively high production costs as compare3 t o p lan t proteins. B a k e r ' s yeast, however, has well-established markets for human food and animal feed. A plant w a s build in 1984 by a j o i n t venture of Kroger and Corning Glass t o produce baker's yeast from hydrolyzed whey permeate. Unfortunately, this program w a s terminated recently due t o economic reasons.

Methane Recent growing concerns about ernriromnental pollution and eneryy crisis

have generated i n t e r e s t i n producing methane from whey and whey permeate through anaerobic digestion. The major advantages of this process are l o w costs, high energy efficiency, and process simplicity a s compared t o other waste treatment m e t h o d s (Yang et a l , 1988). The microbial methanogenic process anaerobically degrades complex organic matter t o the gaseous products, COL and CHI. With a relatively small growth yield of bacteria, about 90% or more of the substrate energy is retained i n the a[. The produced biogas (methane) can be used as a process fuel in cheese manufacturing, or used in a p e r plant to generate electricity (Palmer, 1984).

Currently, approximately 50% of the 57 billion pounds of whey produced annually in the U.S. are not u t i l i zed . Th i s waste product represents an

annual po ten t ia l source of 9 . 5 x tu of energy i f converted t o methane through anaerobic digestion. Saving up t o 70% of natural gas needs i n a cheese p lan t also can be realized by properly converting whey into methane. Figure 6 shows a whey processing plant producing methane f m whey permeate.

Converting whey permeate to methane may pmve t o be an effective solution for the waste and energy problems facing the dairy industry. However, despite the waste reduction and energy potential, anaerobic digestion is not a highly regarded process in the dairy industry, largely due t o the inherent problems associated w i t h current technology. The conventional anaerobic digestion 3

9

1 process suffers from slow startup, slow reaction rate, and unstable reactor performance. As a consequence, this technology is only used at same laqe plank.

The problems with conventional anaerobic digestion arise froan the use of undefined seeding cultures and the cmplicated fermentation kinetics involved in the methanogenic process. Since whey permeate has consistently defined composition, an impruved methanogenic process using defined seeding culture can be developed for producing methane frm whey permeate ( Y a n g et al, 1988). This development wi1l.k important, especially for smaller plants, in order to turn the anaerobic digestion to an ecodcally attractive process.

Another problem with methane production from whey is the low product value: methane at a price of $3.5-5.0. Comparing with other potential fermentation proctucts from whey, anaerobic digestion can be only considered as a waste treatment process with some useful byproduct. However, the major advantage of this process is that the product can be used in the processing plant; there is no marketing problem.

Alcohols Many processes have been developed to utilize whey permeate as a

feedstock for ethanol production. Figure 7 shows a flowsheet for ethanol production from whey permeate. Ethanol fermentation, however, are only used at large dairy plants because the conventional distillation for ethanol recovery requires large scale to justify the costs. New developments in shiltaneous fermentation-separation processes may have great potential to improve the fermentation rate and to cut dum the separation costs, and thus make ethanol fermentation also an attractive process for smaller plants. However, there are still several technical difficulties need to be wercame.

Fuel alcohol at current market prices of $1.2-1.5/gal is no longer an attractive fermentation product from whey permeate. Butanol is another potential product from whey fermentation. But this one have similar, or even more severe, problems for small to medium-size plants, as to those with ethanol fennentation. E!utanol production frm whey is not yet anywhere close to cmmercialization.

,)

10

3 WHEY UF 100.000 Ibs

7% T S

r - I I -

WPC n

-

950 Ibs PERMATE 93aoo Bs 60 crcoon.

5% Lactose 1% Rotein

WFfY M Y PROTEIN

I \

Anaerobic Digestion

EFFLUENT

PCrmC- 16% are Lactotw

WHEY > UF 3 RO > 100,OOO Ibs

7% T.S. 5% Lactose 1% Rotein

Waste Stream (0.4 OcoD/U Methane Production from W h e y Permeate TO WICIPAL SEWERS

8% ' Ethanol -

Ethanol Fetmenrarim

Figure 6. M e t h a n e production f m Whey Permeate.

3 Figure 7. Mhanol production f m Whey Fermeate.

11

O r s a n i c A c i d s Lactic acid (2-hyroxypropanoic acid) is an important chemical w i t h an

annual production of more than 10,000 tomes. It is currently used as both a food addi t ive and an indus t r ia l chemical. Current market prices are about $2.0 per kg lactic acid. Lactic acid can be produced either biologically or s y n t h e t i c a l l y . Homofermentative l ac t ic bac te r i a from the genera of Lactobacillus and Stre~ococcus are usually used i n the fermentation process for l a c t i c acid production fram whey. Organic nitrogen soun=es such as malt extract, corn-steep liquor, yeast extract or undenatured milk must be added in most cases t o provide rapid, dense microbial growth. Iactic acid yields of 92-94% based on the in i t i a l sugar content of the media a r e common i n batch processes. However, the fermentation-produced lact ic acid cannot annpete w i t h l ac t ic acid fmm chemical synthesis a t present t i m e , due t o t h e high cos ts associated w i t h product recovery fram the fermentation broth.

Other organic acids such as propionic, butyric, and citric acids also can be produced from whey fermentation. Among them, citric acid is the only organic acid currently being cammercially produced by fermentation; b u t the market f o r ci tr ic acid is already saturated and very wmpetitive. Unless significant developments in the fermentation technology are achieved, such a s simultaneous extra&ion of organic acids during fermentation to avoid product inhibition and t o reduce cos ts associated w i t h fermentation and recovery processes, organic acids production f m whey permeate w i l l not be econamical. Nevertheless, oryanic acid mixtUre containing acet ic , propionic and butyric acids produced from anaerobic fermentation probably w i l l be more attractive than methane for small t o medium-size plants.

~ -

.

Calcium Maqnesium A c e t a t e Calcium magnesium acetate (CMA) is a mixture of calcium acetate and

magnesium acetate. CMA has a ccrmparable deicing abil i ty t o salt (NaC1) and has been identified as one of the most promisit alternative road deicers by the Federal Highway Adtministration. CMA is noncormsive t o vehicles, is not harmful t o highway conc re t e and vege ta t ion , and has no i d e n t i f i e d environmental concerns. CMA, currently produced by reacting glacial acetic acid w i t h dolomitic l i m e or limestone, is too expensive t o use as a road

\ i

12 t

deicer at current prices; it costs $500/tonne as campared to $20-40/tonne for salt.

~

However, several studies have indicated that low-cost CMA could be readily produced from low-grade biomass, including whey permeate, via anaerobic fermentation. Our prior studies have shcrwn that acetate could be producd fmm whey permeate by an anaerobic fermentation using mixed cultures of homolactic (StreDtococcus lactis) and homoacetic (Clostridium fo~coaoeticum) bacteria (Tang et al, 1988). U n l i k e the conventional vhs~ar (acetic acid) fermentation, this anaerobic process does not aeration and has a close to 100% yield from sugar (compare to <60% yield from the aerobic vinegar fermentation). This process is also superior to other anaerobic processes using either pure culture of homoacetogens (Clostridium thennoaceticum) or mixed cultures of anaerobic bacteria (i.e. anaerobic digestion). Pure culture of anaerobic hamoacetcgen cannot efficiently convert lactose to acetate; while anaerobic digestion produces mixed acids, including acetic, propionic and butyric, with a loa acetate yield (<30%).

A fermentation process for CMA production frm whey penneate is shown in Figure 8 . The advantages of this process include high yield, low costs, simple product recovery method used, and large potential market awaited for the product. About 1.2 lb CMA can be produced from each lb of lactose fermented. It is conceivable that CMA production frm whey permeate will provide a viable solution to whey disposal problem. Moreover, about 1.7 billion lb6 of low-cost CMA can be produced for highway deicing f m the currently unused whey.

mthan Gum

Xanthan gum is a hetero-polysaccharide produced industrially by fermentation of glucose using the bacterium X a n t h m n a s tames tris. h e to its excellent rheological properties, xanthan gum has wide application as a suspending, stabilizing, or thickening agent in the food industry. It is also used as an ennilsifier, lubricant, thickening agent, or mbilitylx>ntrol agent in enhanced oil recovery. Cumenttly, the total U.S. consumption of xanthan is approximately 36 million pounds per year, with an estimated annual gruwth rate of 5% to 10%.

Ca/MgO WPC Dried CMA

Grarules

CMA Production from Whey Permeate 6000 Ibs

Figure 8 . CMA P"uction fram Whey Permeate.

WHEY 100.000

5o/s Lactose 1% Rotern

7% T.S Fermentaticn

LACTOSE m y y s WPC

7 To Alcohol Recovery f .____________ Waste Treatment

Alcohol Precipitation

XANTHAN GUM

3500 Ibs

Centr i fu- Drying gation

F i v 9. Xanthan Gum Proauction f m Whey Permeate.

.

14 4

Whey permeate can be used as a substrate for xanthan gum fermentation, thus lowering the BOD on sewer systems, reducing disposal costs, and generating a high-value marketable product. A study is undertaken to determine the economical feasibility of xanthan gum production fmmwhey penneate (Maldonaldo et al, 1989). As shown in Figure 9, the xanthan gum production process includes i"0bilized enzyme (p-galactosidase) m c t o r s to hydrolyze whey lactose to a mixture of glucose and galactose before fermentation. This lactose hydrolysis step could be eliminated by using

reccanbht XanthamOnas strains that can directly utilize whey lactose as a carbon source. Currently, recombinant strains containing the p-galactosidase gene fmm _E. a i can gruw on lactose, but xanthan gum production from such strains is low. Experiments using hydrolyzed whey lactose have indicated that high yields and high qualities of xanthan gum can be obtained on such media using a variant strain derived from Xanthomonas camDestris NRFU, B-1459. preliminary econdc evaluation of this process appears very promising, even for medium-size plants.

I The major disadvantages of using this prccess are the high costs involved in product recovery and the waste stream fran fermentation requiring further treatnmt before disposal. However, at current prices of -$5.0/lb for food- grade, xanthan gum is'a very attractive potential product f m whey permeate.

Other Fermentation Products As already shown in Table 2, there are many other products can be made

from whey fermentation. Chdcals such as color, flavor and arcma compounds, biodegradable polymers, bioinsecticides, organic acids and alcohols, many food ingredients such as amino acids and vitamins, and many protein products including food enzymes also can be made fmm whey fermentations. Although many of these products have been investigated previously, recent advances in recombinant DNA technologies and bioreactor engineering have revolutionized the production methods and thus w o r t h reevaluating the fermentation processes for their production fram whey permeate. However, perhaps only a few of them will have "ercial significance.

There are many factors need to be considered selecting a fermentation ?his is discussed in the next section. process for whey permeate utilization. 1

15

Factors Affecth Process Selection

There are two driving forces to determine how whey is going to be utilized or disposed; these are needs and incentives. The needs include to remove the waste stream with minimum costs and no pollution to the environment. The dairy industry is compelled by regulations to meet these needs. The incentives include to turn the waste stream into a profitable or usable product and to gain good public image by doing good waste management. Nevertheless, econanics and the available technologies determine the final selection of the process that is most appropriate to each plant.

Table 3 shows the comparison of product values from several whey fermentations with lactose. The product with the highest market value may not be the most desirable fermentation product f m whey permeate. There are m y other factors need to be considered in selecting a fermentation process. Table 4 lists several important factors and compares several fermentation products. The final selection will be depemlent on the plant size and each individual plant situations. Perhaps there is no universal solution for whey utilization and disposal in the dairy industry. An expert system is needed in dealing with the larye knwledge base existing for whey fermentation. The development of an expert system for selection of a most suitable product and process for whey fermentation is underway. An ideal expert system will also include the features of designing and synthesis of an optimal fermentation process.

?

.

Whey presents a major waste disposal problem to the dairy industry. However, with proper uses of whey, this waste product can be a valuable resource for the production of usable and profitable products. Whey fermentation will provide good means for whey utilization and disposal. F'urther developments in whey fermentation will prove to be a profitable effort for the dairy industry.

16

Table 3. product: V a l u e s fmn Several Whey Fermentations.

~

(production fm 100,000 Ibs whey kxessed) product Ouantitv Unit Price Total Value Lactose 3000 Ibs $O.lZ/lb $360

Methane 25,000 cu Et $5/1000 cu Et $125 Ethan01 320 gal $1 9 5/@ $480

CMA 6000 Ibs $0.20/lb $1200 xanthan Gum 3500 Ibs $5. o/lb $17500

Table 4. Caparison of Lactose, Methane, Ethanol, CMA

and xanthan proctuction from whey -te.

Lactose M e t h a n e Ethanol CMA mthan Gum

m-oduct

1. value laW

2. use food

3. market saturate

m-ocesS 1. fermentation no

2. purification easy

3. production costs mcderate

4. waste generation yes

very lm

energy

m u s e

simple

noneed

3Tm

no

medium high very hi*

fuel/foOa deicer thickner

O h Y good campetitive

moderate r"te difficult

moderate simple difficult

moderate low . .

r " a l n 0 Y=

17

References

1. P.H. Boening and V.F. Larsen, Anaerobic fluidized bed whey trea.tment, Biotechnol. Bioeng., 24, 2539 (1982).

2. J.P. Barford, R.G. Cail, I.J. Callander, and E.J. Floyd, Anaerobic digestion of high-strength cheese whey utilizing semiconthous digesters and chemical flocculant addition, Biotechnol. Bioeng., 28, 1601, (1986)

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I.C. Tang, S.T. Yang, and M.R. Okos, Acetic acid production from whey lactose by the co-culture of streptococcus lactis and Clostridium formicoaceticum, Appl. Microbiol. Biotechnol., 28, 138 (1988).

9. USDA Econdc Resear& Service, Dairy situation and outlook report (1989).

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11. S.T. Yang, I.C. Tang, and M.R. Okos, Defined bacterial culture developent for methane generation frcnn lactose, Biotechnol. Bioeng., 32, 28 (1988).

3.

4.

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7.

8. 3

12. S.T . Yang, I.C. Tang, and M.R. Okos, Kinetics of homoacetic fermentation of lactate by Clostridium formicoaceticum, Appl. Environ. Microbiol., 53, 823 (1987).

13. S.T. Yang, M.R. Okos, and J.C. we, Kinetics of methane fermentation of

14. J.G. Zadm-, Lactose, properties and uses. 3. Dairy Sci., 67, 2654 (1984).

15. R.R. Zall, Trends in whey fractionation and utilization, a global Perspective, J. Dairy Sci., 67, 2621 (1984).

16. G. Zellner, P. Vogel, H. Kneifel, and J. Winter, Anaerobic digestion of whey and whey permeate with suspended and immobilized camplex and defined

Whey, Meet. Am. Soc. Agric. Eng., paper No. 82-3592 (1982).

consortia, Appl. Microbiol. Biotechnol., 27, 306 (1987). 1 1