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Appl Microbiol Biotechnol (1995) 43:242-248 Springer-Verlag 1995O R I G I N A L P A P E R

S. Tejayadi M. CheryanLact ic ac id from chee se whey permeate . Product iv i ty and economicsof a cont inuous m em brane b ioreactor

Received: 31 May 1994 / Received last revision: 13 October 1994 / Accepted: 24 October 1994

Abstract The economics of incorporating membranemodules in several steps in the conversion of whey per-meate to lactic acid was studied. Membrane recycle fer-menters operating at a cell concentration of 40 g 1-~re-suited in a productiv ity of 22 .5 g 1-1h ~with a lactateconcentration of 89 g 1-1 and a yield of 0.89. The mem-brane units (reverse osmosis for preconcentrating wheypermeate, hollow-fiber ultrafiltration for clarificationand for cell recycling) contrib ute ab out 28% of the to-tal fixed capital costs and less than 5% of the operatingcost. The two largest costs are whey transportation andyeast extract, contributing about 35% and 38% to thetota l product cost of US $ 0.98/kg 85% lactate . Withoutthese two costs, unpurified lactate could be producedfor $ 0.27/kg.IntroductionCheese whey is a by-product of the cheese manufactur-ing industry with an annual worldwide production ofabout 40.7 x 106 tonnes (40 x 106 tons), half of which isproduced in USA. A large portion of it is treated byultrafiltration to produce whey protein concentrates.However, this process concomitantly produces largequantities of permeate, which contains mostly lactoseand ash. The disposal of the pe rmeate is still a problem.One solution is to convert the lactose by fermentationinto value-added industrial chemicals, such as lacticacid. Lactates are widely used in the food industry asacidulants, preservatives, precursors for stearoyl-2-1ac-tylates and for the production of industrial polymerssuch as polylactic acid and acrylic acid. About half ofthe world's production is made via fermentation. Theremainder is produced via synthetic routes (Vick Roy1985).

S. Tejayadi M. Cheryan (l~)University of Illinois, Agricultural Bioprocess Laboratory,1302 W. PennsylvaniaAvenue, Urbana, IL 61801, USA

Conventional methods of fermentation that use freecells in batch processes have several limitations, such aslow productivity, product inhibition and batch-to-batchvariation in the product, leading to high fermentationcosts (Cheryan 1986; Cheryan and Mehaia 1984; Me-haia and Cheryan 1986, 1987). Continuous fermenta-tion, on the other hand, although overcoming some ofthe problems associated with batch processes, is limitedby cell wash-out. In order to increase the productivitysignificantly, it is necessary to use high cell concentra-tions and to remove the inhibitory product (lactic acid)from the fermentation mixture.Membrane-based cell-recycling bioreactors can sub-stantially improve productivity of fermentation proc-esses, with few of the problems of immobilized cells orcontinuous fermentation systems that use free cells(Cheryan 1986, Mehaia and Cheryan 1986 1987). Amembra ne bioreactor allows us to integrate the fermen-tation and separation steps, thus simultaneously (a)mainta ining high cell density, (b) recycling the cells forfurther use, and (c) continuously removing lactic acidfrom the fermenter.The overall process for the conversion of whey tolactic acid is shown in Fig. 1. This paper focuses on twoaspects: technical factors concerning the membrane re-cycle bioreactor (shown as the fermentation vessel/membrane module loop in Fig. 1) and cost estimates(from the reverse osmosis of the whey permeate to theevaporation step).

Materials and methodsMicroorganismA selected strain of Lactobacillus bulgaricus (a freeze-dried cul-ture from Chr. Hansen's Laboratory, Milwaukee, Wis.) was usedthroughout the study. The bacteria were kept in a frozen form ina dormant state in 0.01 M Na2HPO4 buffer solution at -40 C.They were brought to an active state of growth by transferring thebuffer solution to either of the liquid media described below.

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243Cheese Whey

Y e a s t E x t r a c t

U L T R A F I L T R A T I O Ni

W h e y P e r m e a t e

R E V ER S E O S M O S I S

~ - W h e y P r o t e inC o n c e n t r a t e

W a t e r( f o r r e - u s e )

A l k a l iF= = l

=:1E l I

M E M B R A N ES T E R I L I Z A T I O N R e t e n t a t e( D i s c a r d )&C L A R I F I C A T I O Ni

P e r m e a t eF E R M E N T A T I O N V E S S E L ;~

La c t a t e( P e r m e a t e )

E V A P O R A T I O N I

85% L acta teFig. 1 Scheme of process for convert ing cheese whey into lacticacid. MRB is membrane recycle bioreactor

MediaThe feedstock used for the continuous bioreactor studies waswhey permeate with added yeast extract. Whey permeate powderwas obtai ned from Express Foods Inc. (Lexington, Ky.). This wasthe dried mineral/lactose fraction resulting from the ultrafiltrationof fluid sweet whey. Its composition was 98%-99% total solids,79%-81% lactose, 8%-10% ash and 2.5%-4% protein (N x 6.38).Yeast extract from Difco Laboratories, Detroit, Mich. was usedfor all experimental work reported in this study.The whey permeate powder was suspended in distilled waterto the desired solids concentration, mixed with yeast extract atthe desired concentration and the pH was adjusted with HC1 orNaOH as needed. The medium was cold-sterilized by passing itthrough either a 0.2-1xm cross-flow microfilter (Acroflux capsule,Gelman Sciences, Ann Arbor, Mich.) or an ultrafilter with a100kDa cut-off (obtained from Amicon, Danvers, Mass., or A/GTechnology, Needham, Mass.). The sterile, supplemented wheypermeate was stored in a sterile container at 4C until needed.

BioreactorThe batch fermen ter was a 2-1 glass vessel equ ipped with t emper-ature control, pH controller and agitation. The me mbrane recycle

bioreactor (MRB) has been described earlier (Mehaia and Che-ryan 1986, 1987). The fermenta tion vessel was coupled in a semi-closed loop configuration to a mem bran e module by a pump. Theproduct stream (containing the lactate and unutilized lactose andnutri ents) was withdrawn from the system whereas the cells wererecycled back to the bioreactor. When necessary, a small portionof the retentate was bled off from the MRB to keep the cell den-sity constant. To obtain the higher cell concentrat ions, several cy-cles of fermentation/ultrafiltration/refermentation were con-ducted until the desired cell concentration was reached. Allpumps were Masterflex peristaltic pumps obta ined from ColePalmer, Chicago, Ill.).The membrane recycle bioreactor system was operated as acontinuous stirred tank reactor (CSTR) as determined by a resi-dence time distribution study (Tejayadi 1990). The total fermen-tation volume was kept const ant by matching the feed flow rate tothe permeate flux. During this phase of study, the independentvariables were dilution rate (h -1) 0-1.84, substrate concen tration(g 1-1) 50, 75, 90, 100, and cell concent rat ion (g 1 ~) 5, 10, 12, 20,40. The following parameters were kept fixed: pH at 5.6+0.1 bythe addition of 8M NH4OH, temperature at 45 C and MRB vol-ume at 300 ml. The volume of the MRB included the contents ofthe fermentation vessel, the tube side (retentate channel) of thehollow fiber and the connect ing tubings and fittings.The measured parameters were the concentrations of residualsugars (lactose, glucose and galactose) and product (lactic acid).Samples (5-10 ml) were collected from the permea te and sub-jected to analyses as described later. Samples from the retentatewere collected to measure cell concentration.

Membrane moduleOur earlier studies (Tejayadi and Cheryan 1988) with a hollowfiber module indicated that satisfactory flux could be maintai nedover a long term with lactic acid fermentation broths and thatfouling of the membrane by the cells and media componentscould be controlled within acceptable limits. Reported here arestudies with polysulfone hollow fiber modules, which were ob-tained from A/G Technology, Needham, Mass., Model UFP-30-E-4 with a molecular weight cut-off of 30,000. It contained 104fibers 26.8 cm in length, 1 mm diamete r and 0.035 m 2 surfacearea.

Calculated parametersProductivity (gl -~) = amount of lactate producedfermentation volume x timeYield (Ye/s) (g g - 1 ) _ lactate producedsubstrate utilizedIn a batch fermentation,Productivity = Lactate concentration (gl -t )fermentation time (h)S u b s t r a t e u t i l i z a t i o n (%)= [/Sini t ial -S f i n a l j \ X 1 0 0\ S in i t i a l / .where S is the substrate concentration.In a continuous fermentation, Productivity=lactate concen-tration (g 1q) x dilution rate (h 1)Dilution rate (D)(h - -1) __ product stream flow rate or flux (lh -1)volume of system (1)

S u b s t ra t e u t il iz a ti o n ( % ) = / \(Sinlet-S-~utlet.~ X 1 00\ Sinle t /

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244Analytical methods

8tLactose, glucose, galactose and lactic acid concentrations weremeasured by HPLC. An Aminex HPX-87H column (BioRad,Richmond, Calif.) was used w ith 0.005 M H2SO4 as the elua nt at aflow rate of 0.8 ml/min at 65 C. A refractive index dete ctor (Wa- q- 6oters Associates) was used with a Fisher recorder.Cell concentra tion was dete rmin ed optically at 525 nm a ndthen calibr ated with dry weight. Cells wer e centrifuged, was hed '~ 40with distilled water twice and dried at 70 C until constan t weightwas obtained.

o20

ResultsM e m b r a n e r e cy c le b i o r e a c to rF i g u r e 2 s h o w s a t y p ic a l l o n g - t e r m s t a b i li t y s t u d y o f t h em e m b r a n e r e c y c l e b i o r e a c t o r o p e r a t e d a t a d i l u t i o nr a t e o f 0. 5 h -1 a n d a n a v e r a g e c e l l c o n c e n t r a t i o n o f 4 0 g1- 1. A g r a d u a l a p p r o a c h t o s t e a d y s t a t e a n d c o m p l e t es u b s t r a t e u t i l i z a t i o n w a s o b s e r v e d . A f t e r 1 3 0 h o f o p e r -a t ion , the l ac ta te concen t ra t ion was 46 g 1 -1 wi th an in i -t i al l a c t o s e c o n c e n t r a t i o n o f 5 0 g 1- l , resu l t ing in a p ro -duc t iv i ty o f 23 g l -ah -1. Increas ing the subs t ra te conc en -t ra t ion to 75 g 1-1 resu l t ed in i t i a lly in a d r am at ic de-c r e a s e i n p e r f o r m a n c e , b u t t h e M R B e v e n t u a l l y s t a b i l -i zed a t a l ac t i c ac id concen t ra t ion o f 70 g 1 -1 and a p ro -duct iv i ty of 35 g 1-~h-1.

F i g u r e 3 s h o w s a n o t h e r l o n g - t e r m s t a b i l i t y s t u d yc o n d u c t e d w i t h d i f f e r e n t v a r i a b l e s . T h e i n i t i a l s u b s t r a t econ cen t ra t ion was 100 g 1-1 and the d i lu t ion r a te w asf i r s t s e t a t 0 .5 h -1. Th i s com bin a t io n o f conc en t r a t ion sa n d d i l u t i o n r a t e w a s t o o m u c h f o r t h e M R B , r e s u l t i n gin fa i r ly h igh l eve l s o f unu t i l i zed l ac to se and ga lac tosei n th e b r o t h e v e n a f t e r 1 5 0 h o f o p e r a t i o n . L o w e r i n gthe d i lu t ion ra te to 0 .25 h -1 resu l t ed in 99% subs t ra teu t i l i z a t i o n a n d c o r r e s p o n d i n g l y h i g h e r l a c t i c a c i d c o n -cen t ra t ion o f 89 g 1 -1 , wi th a p rod uc t iv i ty o f 22 g1-1h-1.

L-1 h-1MRB, X=4 0g , D = 0 .5-- So = 50gC 1 -~.-[,t -- So= 75 gC 1~

O #0

. ,oo,oso I f25 50 75 1 O0 125 150 175 200 225

Time (Hours)Fig. 2 Perform ance of MRB with whey permeate. Cell concentra-tion (X) w as 40 g 1-1, and dilution rate (D) was ke pt at 0.5 h -1

.-It.-o.#,ot-ot,.)

100E

8 0

6 0

MRB, X= 40 gI 1, $o= 100 g l21

4 0 ~

2 0

0 0

4 D=0 .5 h-1 ~l " D=0 "25 h-1 ~"

"" ,~c~ Lac tose

4 0 8 0 1 2 0 1 6 0 2 0 0 2 4 0 2 8 0Time (hours)

Fig. 3 Stability of MR B a t a cell conce ntration of 40 g 1 t and in-let lactose co ncentr ation of 100 g 1-1. The dilution rate was variedas shown in the figureP r o c e s s d e s i g nT h e s i n g l e m o s t i m p o r t a n t f a c t o r c o n t r o l l i n g p r o d u c -t i o n o r o p e r a t i n g c o s t i s t h e l a c t a t e c o n c e n t r a t i o n ( P )f r o m t h e M R B , b e c a u s e i t d e t e r m i n e s s e v e r a l d e s i g np a r a m e t e r s . T h e o t h e r p a r a m e t e r s c a n b e c a l c u l a t e d a sfo l lows :

1 . S u b s t r a t e c o n c e n t r a t i o n t o u s e i n t h e f e e d t o t h er e a c t o r ( S ) , w h e r e S = P/Ye/sT h i s i s a l s o t h e s u b s t r a t e c o n c e n t r a t i o n f r o m t h e r e -v e r s e o s m o s i s u n i t . T h e d e g r e e o f c o n c e n t r a t i o n n e c e s -s a r y i n t h e r e v e r s e o s m o s i s s y s t e m i s t h e c o n c e n t r a t i o nf a c t o r ( X ) , w h e r e X = S / S 0 , So b e i n g t h e s u b s t r a t e c o n -c e n t r a t i o n i n t h e f e e d ( i n t h i s c a s e , t h e l a c t o s e c o n c e n -t r a t i o n i n t h e w h e y p e r m e a t e , 4 5 g 1 1). T h e r e f o r e , i f t h ew h e y p e r m e a t e t o b e p r o c e s s e d o n a n h o u r l y b a s is is W ,t h e n t h e f l o w r a t e o f t h e r e v e r s e o s m o s i s r e t e n t a t e( F a o ) i s g i v e n b y F R o = W/X.

2 . T h e m e m b r a n e a r e a f o r t h e R O s y s t e m w i l l i n -

c r e a s e w i t h a n i n c r e a s e i n P : m e m b r a n e a r e a =(W-Fno)/Jnow h e r e J n o i s t h e f l u x o f t h e r e v e r s e o s m o s i s s y s t e m .F l u x w a s e s t i m a t e d f r o m t h e d a t a o f S c h l i c h e r a n d C h e -r y a n ( 1 9 90 ), f r o m w h i c h m e m b r a n e p e r m e a b i l i t y c o e ff i -c i e n t s a n d o s m o t i c p r e s s u r e d a t a f o r a t h i n - f i l m c o m -p o s i t e m e m b r a n e w e r e o b t a i n e d . T h i s m e m b r a n e i sa v a i l a b l e i n a s p i r a l - w o u n d c o n f i g u r a t i o n , w h i c h t o d a yc o s ts a b o u t U . S . $ 3 0 0/ m 2 f o r t h e c o m p l e t e p l a n t , i n -c l u d i n g t h e f i r s t s e t o f m e m b r a n e s [ p e r s o n a l c o m m u n i -c a t i o n ( 1 9 9 3 ) , F i l t r a t i o n E n g i n e e r i n g , N e w H o p e ,M i n n . ; N i r o F i l t r a t i o n H u d s o n , W i s . ; O s m o n i c s I n c . ,M i n n e t o n k a , M i n n . [ .

3 . T h e m e m b r a n e a r e a f o r t h e m e m b r a n e e l a r i f i e r /s t e r i li z e r s y s t e m w il l d e c r e a s e a s P i n c r e a s e s. A s s u m i n ga 5 % l o s s o f t h e r e v e r s e - o s m o s i s - c o n c e n t r a t e d w h e yp e r m e a t e i n t h i s s y s t e m : m e m b r a n e c l a r i f i e r / s t e r i l i z e ra re a = 0 .95 (Ftao)/JsTEn.

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14 012 0

E 100vE 8 0o 60>

402o&" 1200E 1000

800 0 ~ 1 2v 8

I I I 1

I F4 40 60 810 100 120L a c t a t e C o n c e n t r a t i o n ( g k-1 )

Fig. 5 Effect of lactate concentration in the MRB o n productivity(at maximum yield of product and substrate utilization) and onthe amount of water to be evaporated to produce 85% lactate

4 . T h e m em b ran e a r ea fo r t h e u l t r a f i l t r a t i o n u n i t i nthe MRB wi l l decrease as P increases . Assuming a losso f 1 % o f t h e f l o w i n t o t h e M RB as ce l l b l eed : M RBul t raf i l t ra t ion area = (0.99) (0 .95) (FRo)/JMRB.The val -ues o f f lux for the above two cases (J sTeR and JMRB )w ere o b t a i n ed i n o u r l ab o ra t o ry (T e j ay ad i an d Ch ery an1988; Tejayadi 1990).

5 . The d i lu t ion ra te (D) wi l l decrease wi th an in -crease in P . This can be ob ta ined f rom Fig . 5 , s inceD = p ro d u c t i v i t y / P .

6 . T h e v o l u m e o f t h e M RB w i ll in c reas e w i t h P : v o l-ume = (0.99) (0.95) FRO/DThese fac tors are shown in Fig . 4 as a funct ion ofp ro d u c t co n cen t r a t i o n (P ) . T h e n e t e f f ec t o f t h e v a r i o u sfactors on the product ion cos t i s shown in Fig . 5 (bo t -t o m ) . T h e am o u n t o f y eas t ex t r ac t n eed ed i s a fu n c t i o no f t h e f l o w r a t e o f t h e s u b s t r a t e i n t o t h e M RB ( i . e . , afunct ion of FRO, which decreases as P increases ) . Thus ,t h e am o u n t o f y eas t ex t r ac t n eed ed w i l l d ec reas e a s Pincreases . Yeas t ex t rac t i s the l arges t s ing le opera t ingcos t in the analys i s . Figure 4 a l so shows the opera t ingcos t minus the yeas t ex t rac t cos t as a funct ion of p rod-uct concent ra t ion . In th i s case , the product ion cos t be-co m es m u ch l e s s d ep en d en t o n t h e l ac t a t e co n cen t r a -t i o n f r o m t h e M R B .

E co n o m i c an a l y s i sCo s t e s t i m a t e s a r e b as ed o n t h e a s s u m p t i o n t h a t300 x 1061 of whey permeate (conta in ing 4 .5% lac tose)i s avai lab le per year (300 opera t ing days /year) . Theeco n o m i c an a l y s i s h as b een d o n e f ro m t h e r ev e r s e o s -mos i s s t ep to the evaporat ion s tep shown in Fig . 1 . An-n u a l p r o d u c t i o n w o u l d b e a b o u t 1 2 x l 0 6 k g ( a b o u t26x1061b) 85% lact i c ac id , assuming a YP/s of 0.89.Bas ed o n t h e p ro ces s d es i g n o u t l i n ed ea r l i e r , t h e d a i l yproduct ion of 85% lacta te i s 44712 kg . Standard cos t sa r e t ak en f ro m s ev e ra l s o u rces i n d i ca t ed i n t h e t ab l e s ,a s w e l l a s f ro m A x t e l l an d Ro b er t s o n (1 9 8 6 ) , G ar r e t t(1989) , Rei sman (1988) and Remer and Chai (1990) .Co s t s g i v en i n t h o s e s o u rces w ere av e rag ed an d ad -j u s t ed b y u s i n g t h e Co n s u m er P r i ce In d ex p u b l i s h ed i ncurren t i s sues o f Chemical Engineering (M cG raw -H i l l ,N ew Y o rk ) . T h e co s t o f co n v e r t i n g t o t h e ac i d fo rm o flac t ic ac id i s no t inc lude d in th i s analys i s .

Table 1 shows the to ta l f ixed cap i ta l inves tment re-q u i r ed fo r t h e ch ees e w h ey p e rm ea t e - t o - l ac t a t e p l an t .T h e m em b ran e u n i t s ( r ev e r s e o s m o s i s an d u l t r a f i l t r a -t i o n ) co n t r i b u t e ab o u t 2 8 % o f t h e t o t a l f i x ed cap i t a lcosts .

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24 6Table 1 Fixed capital investment o f whey permeate-to-lactate plant Basis: produc t ( lactate) concentration from m em brane recyclebiorea ctor (M RB) = 89 g 1-Item Size Unit cost Cost ($) R eferenc ea($/m 2)Direct costs1. Installed equipment

UltrafiltrationSterilization 350 m 2MRB 560 m 2Rev erse osmosis 350 m 2Ferm entatio n vessel ( including agitator) 72000 1Holding tank for whey perm eate i x 1061Holding tank for yeast extract 4700 1Mixing tank 25 0001Seed culture tank 4001Six-stage multiple-effect evap oratorTotal installed equipment2. P iping, wiring, instrumentation (30% of 1)3. B uildings (10% of 1)4. Land improvements (5% of 1)5. Total direct costs

Indirect costsContingencies, engineering, contracting fees (27.5% of 5)Fixed capital investmentWorking capital (15% of fixed capital)Tota l capital investment

900 315000 1900 504000 1300 105000 2100000 3,4150000 511000 555000 53000 5700000 61943000582900 7194300 797200 72817400775600

3593000538950

4131950a I Personal comm unication (1993) A/G Technology, Needham,Mass.; Koch/Romicon, W ilmington, Mass.; CeraMem Corp., Wal-tham, Mass.; U.S. Filter, Warrendale, Pa, 2 Personal communica-tion (1993) Filtration Engineering, New Hope, Minn.; Niro Filtra-

tion, Hudson, W is.; Osmonics Inc., Minnetonka, Minn . 3 Reisman(1988). 4 Pace and Goldstein (1975). 5 Naser and F ournie r (1988).6 Personal communication (1993) Swenson Process Equipm entInc., Harvey, I ll. 7 Peters and T immerhaus (1988)

T a b l e 2 s h o w s t h e o p e r a t i n g c o s t s a n d p r o d u c t i o nc o s t , a s s u m i n g ( a ) t h e w h e y p e r m e a t e w a s o b t a i n e df r o m a c h e e s e f a c t o r y s i t u a t e d 1 6 0 k m ( 1 0 0 m i l e s ) f r o mt h e l a c t i c a c i d p l a n t a n d w a s t r a n s p o r t e d b y r o a d , a n d( b ) t h e r e w a s n o c o s t o f t h e w h e y p e r m e a t e . I n t h i sc a s e , t h e t w o l a r g e s t c o s t s a r e w h e y t r a n s p o r t a t i o n a n dy e a s t e x t r a c t , c o n t r i b u t i n g a b o u t 3 5 % a n d 3 8 % t o t h et o t a l p r o d u c t c o s t .

Discussion

T h e g o a ls i n a n y i n d u s tr i a l f e r m e n t a t i o n p r o c e s s s h o u l db e :1 . M a x i m u m p r o d u c t i v i t y , t o m i n i m i z e c a p i t a l a n d o p e r -a t i n g c o s t s2 . M a x i m u m p r o d u c t c o n c e n t r a t i o n , t o m i n i m i z e d o w n -s t r e a m ( c o n c e n t r a t i o n ) c o s t s3 . M a x i m u m s u b s t r a t e u t i l i z a t i o n , t o m i n i m i z e f e e d -s t o c k c o s t s4 , M a x i m u m y i e l d ( Y P / s ) , t o m i n i m i z e b y - p r o d u c t f o r -m a t i o n a n d c o n s e q u e n t d o w n s t r e a m ( s e p a r a t i o n )co s ts .H o w e v e r , i t is w e l l -k n o w n i n h i g h -r a t e f e r m e n t a t i o np r o c e s s e s t h a t , u n d e r c o n d i t i o n s o f h i g h e s t s u b s t r a t eu t i l i z a t i o n a n d y i e l d , h i g h p r o d u c t c o n c e n t r a t i o n a n d

h i g h p r o d u c t i v i t y a r e m u t u a l l y e x c l u s i v e . F i g u r e 5 ( t o p )s h o w s s u c h a r e l a t i o n s h i p f o r o u r p r o c e s s . T h e l i t e r a -t u r e i n d i c a t e s t h a t p r o d u c t i v i t i e s i n b a t c h f e r m e n t o r sr an g e f ro m i g 1 -1 h -1 to 7 .5 g 1 -1 h 1 ( th i s d o e s n o t in -c l u d e t h e c y c l e t i m e o f t h e f e r m e n t o r s ) . I n o u r l a b o r a -t o r y , p r o d u c t i v i t i e s r a n g e d f r o m 4 . 5 g l - l h -1 a t 1 1 7 g 1-1l a c t a t e ( M e h a i a a n d C h e r y a n 1 9 8 7 ) t o 7 .5 g 1- 1h 1 a t4 3 g 1-1 ( T e j a y d i 1 9 9 0 ) . I n c o n t r a s t , t h e M R B c o u l da c h i e v e m u c h h i g h e r p r o d u c t i v i t i e s , b u t a t l o w e r p r o d -u c t c o n c e n t r a t i o n . A s a r e s ul t , h i g h e r a m o u n t s o f w a t e rh a v e t o b e r e m o v e d a t h i g h e r p r o d u c t i v i t i e s . T h i s i ss h o w n i n t h e b o t t o m p o r t i o n o f F i g . 5 . T h e r e i s a s t e e pi n c r e a se i n th e a m o u n t o f w a t e r r e m o v a l r e q u i r e d b e -l o w 8 0 g 1-1 l a c t a t e , w i t h n o t m u c h c h a n g e a b o v e 1 0 0 g1-1"

T h e w h e y t r a n s p o r t a t i o n c o s t c o u l d b e r e d u c e d b yi n s t a l l i n g t h e l a c t i c a c i d p l a n t i n t h e s a m e l o c a t i o n a st h e c h e e s e p l a n t . I t w o u l d e l i m i n a t e t h i s c o s t f r o m T a -b l e 2 a n d r e d u c e t h e c o s t f r o m $ 0 . 9 8 / k g t o $ 0 . 6 4 / k g . I fi t i s n o t f e a s i b l e t o l o c a t e t h e l a c t i c a c i d p l a n t i n t h es a m e v i c i n i t y a s t h e w h e y p l a n t , t h e n a t l e a s t t h e w h e yp e r m e a t e s h o u l d b e c o n c e n t r a t e d 2 . 2 t i m e s b e f o r et r a n s p o r t a t i o n , i . e . , t h e r e v e r s e o s m o s i s s h o u l d b e d o n ea t t h e w h e y p l a n t. T h i s w o u l d r e d u c e t h e t r a n s p o r t a t i o nc o s t i n T a b l e 2 t o l e s s t h a n h a l f t h e a m o u n t , r e d u c i n gt h e p r o d u c t i o n c o s t f r o m $ 0. 9 8 /k g t o $ 0 . 7 9/ k g o f 8 5 %l a c t a t e .

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24 7T a b l e 2 O p e r a t i n g c o s t s f o r l a c t a t e p la n t . S a m e b a s i s a s T a b l e 1 . W h e y p e r m e a t e i s a v a i la b l e fr o m a c h e e s e o r w h e y p r o c e s s i n g p l a n ts i t u a t e d 1 6 0 k m ( 10 0 m i l e s ) f r o m t h e l a c t i c a c i d p l a n t (UF u l t r a f i l t r a t ion , RO r e v e r s e o s m o s i s )I t e m U n i t Q u a n t i t y C o s t P e r c e n ta g e o f R e f e r e n c e ac o s t p e r d a y ( S / d a y ) t o t a l c o s tO p e r a t i n g c o s t s1 . R a w m a t e r i a l s

W h e y p e r m e a t e $ 1 . 5 0 /1 0 0 1 1 06 1( t r a n s p o r t a t i o n c o s t )Yea s t ex t rac t $ 3 .85 /kg 4 320 kgA m m o n i u m h y d r o x i d e $ 1 .1 0 /1 1 90 1Sulfu ric acid $ 0 .88/kg 955 kg2 . U t i l i t i e s ( e x c l u d in g e v a p o r a t i o n )W ate r $ 0 .26 /1000 1E l e c t r i c i t y $ 0 . 0 6 /k W h3 . E n e r g y c o s t s f o r e v a p o r a t i o nSte am (50 lb/in2; 3 .5 kg/cm 2) $11 /100 0 kg 82000 kg4 . L a b o r $ 1 5 / h 5 0 h5 . M e m b r a n e sR e p l a c e m e n t $ 6 0 0/ m 2 ( U F )C l e a n i ng $ 1 0 0 / m 2 ( R O )6 . M a i n t e n a n c e a n d r e p a i r s ( 6 % o f f ix e d c a p i t a l i n v e s t m e n t / y e a r )7 . O p e r a t i n g s u p p l i e s ( 2 % o f f i x e d c a p i t a l i n v e s t m e n t / y e a r )8 . P lan t ove rhead (70% of 4 , 6 , 7 )F i x e d c h a r g e s1 . D e p r e c i a t i o n ( 2 0 % p e r y e a r o f f i x e d c a p i t a l i n v e s t m e n t )2 . I n s u r a n c e ( 1 % p e r y e a r o f f i x e d c a p i t a l i n v e s t m e n t )G e n e r a l a n d a d m i n i s t r a t i v e e x p e n s e s ( 5 % o f m a n u f a c t u r i n g c o s t )

15000 34.6

T o t a l p r o d u c t i o n c o s t / d a yCos t o f 85% lac ta te = $ 43383 /day fo r 44712 kg /day = $ 0 .98 /kg

16632 38.3210 0.5840 1.977000 1 20 0.1 31 4 00 k W h 8 4 0 .2 3

900 2.1 3-7750 1.71937 4.5 8 , 950 0 .1 8 ,9826 1.9 10275 0.6 10

876 2.0 l02754 6.3 10138 0.4 102090 4.8 10

43383 100

a 1 L e n z a n d Mo r e i r a ( 1 9 8 0 ) . 2 P e r s o n a l c o m m u n i c a t i o n ( 1 9 9 2 )U n i v e r s a l F o o d s R e d S t a r D i v i s i o n , Mi l w a u k e e , Wi s . ; S h e f f i e l dP r o d u c t s ( Q u e s t I n t e r n a t i o n a l ) , S a r a s o t a , F l a . ; 3 P e r s o n a l c o m -m u n i c a t i o n ( 19 9 3) f r o m l o c a l u t i l i ty c o m p a n i e s . 4 A x t e l l a n d R o -be r t son (1986) . 5 Gar re t t (1989) . 6 Pe r sona l communica t ion ,S w e n s o n P r o c e s s E q u i p m e n t I n c ., H a r v e y , I ll . 7 G i e n g e r a n d R a y

( 19 8 8) . 8 P e r s o n a l c o m m u n i c a t i o n ( 1 9 93 ) A / G T e c h n o l o g y , N e e d -h a m , Ma s s . ; K o c h / R o m i c o n , Wi l m i n g t o n , Ma s s . ; C e r a Me m C o r p . ,Wa l t h a m , Ma s s . ; U . S . F i l t e r , Wa r r e n d a l e , P a . 9 P e r s o n a l c o m m u -n i c a t i o n ( 1 9 9 3 ) F i l t r a t i o n E n g i n e e r i n g , N e w H o p e , Mi n n . ; N i r oF i l t r a t i o n , H u d s o n , Wi s . ; O s m o n i c s I n c . , Mi n n e t o n k a , Mi n n . 10P e t e r s a n d T i m m e r h a u s ( 1 9 8 8 )

T h e cu r r en t m ar k e t p r i ce o f l ac t i c ac i d i s $ 1 .6 0 - $2 .2 0 / k g , d ep en d i n g o n t h e f o r m o f t h e l ac t a t e ( ac i d o rs a l t ) , t h e s t r e n g t h ( 6 0 % - 8 5 % ) a n d p u r i t y ( p e r s o n a lc o m m u n i c a t i o n 1 9 9 3 : A D M , D e c a t u r , I l l . ; P u r a c I n c . ,A r l i n g t o n H e i g h t s , I l l . ; S t e r l i n g C h em i ca l s , H o u s t o n ,T ex . ; E co - C h em , A d e l l , Wi s . ) . I f t h e l ac t i c ac i d w er e t ob e u s e d f o r t h e m a n u f a c t u r e o f b i o d e g r a d a b l e p o l y m -e r s , i t w o u l d h a v e t o b e c o n s i d e r a b l y p u r e r t h a n t h a tp r o d u c e d b y a f e r m e n t a t i o n p r o c e s s . T h u s , t h e p r o d u c -t i o n co s t m u s t b e l o w er ed ev en f u r t h e r , e s p ec i a l l y i f t h ew h e y p e r m e a t e i s t o b e p u r c h a s e d ( o u r a n a l y s i s a s -s u m e d t h e w h e y p e r m e a t e i s a v a i l a b l e a t n o c o s t ) .T h e m e m b r a n e - r e l a t e d c o s t s a c c o u n t f o r l e s s t h a n5 % o f t h e o p e r a t i n g co s t . Po l y m er i c u l t r a f i l t r a t i o n h o l -l o w - f ib e r m e m b r a n e s w e r e u s e d f o r t h e p r o c e s s d e si g n.C o n t i n u i n g i m p r o v e m e n t s i n m e m b r a n e t e c h n o l o g yco u l d l o w er t h i s co s t f u r t h e r i n t h e n ea r f u t u r e . Fo r ex -a m p l e , a l t h o u g h c e r a m i c / i n o r g a n i c m e m b r a n e s a r em o r e e x p e n s i v e , t h e y h a v e m u c h l o n g e r o p e r a t i n g l i f e -t i m es an d g en e r a l l y m u ch h i g h e r f l u x f o r t h i s ap p l i ca -t i o n . T h u s t h e y m a y p r o v e t o b e m o r e e c o n o m i c a l t h a np o l y m e r i c m e m b r a n e s i n t h e l o n g t e r m . E l e c t r o d i a l y s i sc o u l d a l s o b e u s e d t o r e d u c e t h e d o w n s t r e a m c o s t s( Y en an d C h e r y an 1 9 9 1 , 1 9 9 3 ) .

T h e r em a i n i n g l a r g e co s t i s t h e n u t r i en t co s t . T h en u t r i en t ( y eas t ex t r ac t ) l ev e l s u s ed i n o u r ex p e r i m en t s( 1 0 g 1- 1) w er e b as e d o n p r ev i o u s w o r k i n o u r l a b o r a t o -r y t h a t i n d i ca t ed t h i s f e r m en t a t i o n w as c r i t i c a l l y d e -p en d en t o n ce r t a i n n u t r i en t s av a i l ab l e f r o m t h e y eas tex t r ac t . F i n d i n g a ch eap e r n u t r i en t an d ad ap t i n g t h e s e -l ec t ed l ac t i c cu l t u r e t o t h a t n u t r i en t w i ll b e a k ey f ac t o ri n t h e co m m er c i a l s u cces s o f t h i s p r o ces s .Acknowledgements T h i s p r o j e c t w a s s u p p o r t e d i n p a r t w i t hf u n d s f r o m t h e I l l in o i s A g r i c u l t u r a l E x p e r i m e n t S t a t i o n , t h e S t a t eo f I l l i n o i s V a l u e - A d d e d P r o g r a m a n d c o n t r i b u t i o n s o f m e m -b r a n e s f r o m A / G T e c h n o l o g y , N e e d h a m , M a s s . , a n d R o m i c o n ,W o b u r n , M a s s.

References

Axte I1 O , Rober t son JM (1986) Economic evaluation in the chem-ical process industries. W i l e y , N e w Y o r kC h e r y a n M (1986)Ultrafiltrafion handbook. T e c h n o m i c , L a n c a s -t e r , P e n nC h e r y a n M, Me h a i a MA ( 1 9 8 4 ) E t h a n o l p r o d u c t i o n i n a m e m -b r a n e r e c y c l e b i o r e a c t o r : c o n v e r s i o n o f g l u c o s e u s i n g Saccha-romyces cerevisiae. P r o c e s s B i o c h e m 1 9 : 2 0 4 - 2 0 8

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24 8G a r r e t t D E ( 1 9 8 9 ) C h e m i c a l e n g i n e e r i n g e c o n o m i c s . V o n N o s -t r a n d R e i n h o l d , N e w Y o r kG i e n g e r J K , R a y R J ( 1 9 8 8 ) M e m b r a n e b a s e d h y b r i d p r o c e s s e s .A I C h E S y r u p S e r [ 2 6 ] 8 4 : 1 6 8 - 1 7 7L e n z T G , M o r e i r a A R ( 1 9 8 0 ) E c o n o m i c e v a l u a t i o n o f t h e a c e -t o n e - b u t a n o l f e r m e n t a t i o n . I n d E n g C h e m P r o d R e s D e v19:478-483M e h a i a M A , C h e r y a n M ( 1 9 8 6 ) L a c t i c a c i d f r o m a c i d w h e y p e r -

m e a t e i n a m e m b r a n e r e c y c l e b i o r e a c t o r . E n z y m e M i c r o b i a lT e c h n o l 8 : 2 8 9 - 29 2M e h a i a M A , C h e r y a n M ( 1 9 8 7 ) P r o d u c t i o n o f l a c t i c a c i d f r o ms w e e t w h e y p e r m e a t e c o n c e n t r a t e s . P r o c e s s B i o c h e m2 2 : 1 8 5 - 1 8 8N a s e r S F , F o u r n i e r R L ( 19 8 8) A n u m e r i c a l e v a l u a t i o n o f a h o l l o wf i b e r e x t r a c t i v e f e r m e n t o r p r o c e s s f o r t h e p r o d u c t i o n o f e t h a -n o l . B i o t e c h n o l B i o e n g 3 2 : 6 2 8 - 6 3 8P a c e G W , G o l d s t e i n D J ( 1 9 7 5 ) E c o n o m i c a n a l y s i s o f u l t r a f i l t r a -t i o n - f e r m e n t a t i o n p l a n t s p r o d u c i n g w h e y p r o t e i n a n d S C Pf r o m c h e e se w h e y . In : T a n n e n b a u m S R , W a n g D I C ( e d s. ) S i n -g le Ce l l Pro te in I I . M I T P r e s s , C a m b r i d g e , M a s s , p p . 3 3 0 - 3 4 3P e t e r s M S , T i m m e r h a u s K D ( 1 9 8 0 ) P l a n t d e s i g n a n d e c o n o m i c sfor chemica l eng ineers . M c G r a w - H i l l , N e w Y o r k

R e i s m a n H B ( 1 9 8 8 ) E c o n o m i c a n a ly s is o f f e r m e n t a t i o n p r oc e ss .C R C , B o c a R a t o n , F 1 aR e m e r D S , C h a i L H ( 19 9 0) D e s i g n c o s t fa c t o r s f o r s c al i n g - u p e n -g i n e e r i n g e q u i p m e n t , C h e m E n g r P r o g r 8 6 ( 8 ) : 7 7 - 8 2S c h l i c h e r L R , C h e r y a n M ( 1 9 9 0 ) R e v e r s e o s m o s i s o f l a c t i c a c i df e r m e n t a t i o n b r o t h s . J . C h e m . T e c h n o l . B i o t e c h n o l .4 9 : 1 2 9 - 1 4 0Tejayad i S (1990) F e r m e n t a t i o n o f w h e y p e r m e a t e t o l a ct ic a c i d i nh igh ce l l dens i ty b ioreac tors . P h D t h e s is , U n i v e r s i t y o f I l l in o i s ,U r b a n aT e j a y a d i S , C h e r y a n M ( 1 9 8 8 ) D o w n s t r e a m p r o c e s s i n g o f l a c t i ca c i d - w h e y p e r m e a t e f e r m e n t a t i o n b r o t h s b y h o l l o w f i b e r u l -t r a f i l t r a t i o n . A p p l B i o c h e m B i o t e c h n o l 1 9 : 6 1 - 7 0V i c k R o y T B ( 1 9 8 5 ) L a c t i c a c i d . I n : M o o - Y o u n g M ( e d ) , C o m -p r e h e n s i v e b i o t e c h n o lo g y , 1 s t ed n , v o l 3 . P e r g a m o n P r e s s , N e wY o r k , p p 7 6 1 - 7 8 9Y e n Y H , C h e r y a n M ( 1 9 9 1 ) S e p a r a t i o n o f l a c t i c a c i d f r o m w h e yp e r m e a t e f e r m e n t a t i o n b r o t h b y e l e c t r o d i a ly s i s . T r a n s I n s tC h e m E n g ( U K ) . 6 9 : 2 0 0 - 2 0 5Y e n Y H , C h e r y a n M ( 19 9 3) E l e c t r o d i a l y s i s o f m o d e l l a c ti c ac i ds o l u t i o n s . J F o o d E n g 2 0 : 2 6 7 - 2 8 2