20 Chemicals by Fermentation—An Overview
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ROGER WILLIAMS, JR. Roger Wiliams Technical and Economic Services Inc., Princeton, N.J. 08540
Fermentation c e r t a i n l y i s the oldest unit process i n organic chemistry. When f e r m e n t a t i o n b e c a m e comm e r c i a l i s l o s t i n t h e m i s t s o f t i m e , b u t many o f u s t h i n k o f t h e heyday o f f e r m e n t a t i o n as o c c u r r i n g d u r i n g W o r l d War I I , when e t h a n o l was made f o r b u t a d i e n e manufacture. T h e r e a f t e r f e r m e n t a t i o n was r e p l a c e d b y petrochemical sources. T h a t was t r u e o f e t h a n o l , ' i n d u s t r i a l a l c o h o l ' , a s t h e f i r s t c h a r t ( F i g u r e 1) s h o w s . Note t h a t t h i s i s i n d o l l a r s , n o t pounds; and t h a t a l l t h e d a t a have been c o n v e r t e d t o 1975 d o l l a r s t o w i p e o u t t h e e f f e c t s o f inflation. One t h i n g t h a t may s u r p r i s e some, i s t h a t the e t h a n o l b u s i n e s s , i n r e a l d o l l a r terms, r e a l l y has n o t g r o w n i n t h e 50 y e a r s f r o m 1 9 2 5 t o 1 9 7 5 . 1
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Hickson; Sucrochemistry ACS Symposium Series; American Chemical Society: Washington, DC, 1977.
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Of c o u r s e t h e o t h e r p a r t o f t h e e t h a n o l b u s i n e s s , a l c o h o l i c b e v e r a g e s , s u p p o s e d l y was a z e r o b u s i n e s s i n 1925. I t was n o t , b u t t h e r e a r e n o s t a t i s t i c s a v a i l able on moonshine. T o d a y t h e l i q u o r b u s i n e s s i s $1.9 b i l l i o n , a n d b e e r i s a h e f t y $4.8 b i l l i o n . In t o t a l , a l c o h o l i c b e v e r a g e s c o n s t i t u t e a $7.8 b i l l i o n b u s i n e s s based e n t i r e l y on fermentation. Production of butanol-acetone-ethanol j o i n t l y by fermentation i s another o l d process which f e l l by the wayside t o petrochemistry. I t may b e c o m i n g b a c k , a s w i l l b e d i s c u s s e d b y D r . F r a n k Wynn H a y e s , l a t e r . At i t s peak, i n t h e U n i t e d S t a t e s , the output probably h i t $100 m i l l i o n p e r y e a r , i n 1 9 7 5 d o l l a r s . The w h o l e a n t i b i o t i c s b u s i n e s s h a s come i n t o b e i n g s i n c e 1925. F i g u r e 2 shows t h i s b u s i n e s s s i n c e 1 9 5 0 , a g a i n i n 1975 d o l l a r s . The c r a s h i n p r i c e s i n 1965 i s very evident. T h e f i g u r e s shown i n c l u d e a l l t h e a n t i biotics, A l t h o u g h some a r e s y n t h e t i c , t h e y a r e i n a minority. Thus, a n t i b i o t i c s comprise another t h r e e q u a r t e r s o f a b i l l i o n d o l l a r business based on ferment a t i o n , t h a t d i d n o t e x i s t 50 y e a r s a g o . 2000|
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L e t u s c o n s i d e r c i t r i c a c i d , and f u m a r i c , l a c t i c , i t a c o n i c , a n d t h e o t h e r a c i d s t h a t a r e made b y f e r m e n tation. T o d a y , p e r h a p s , t h e y a r e a $100 m i l l i o n b u s i n e s s t h a t was n o n - e x i s t e n t 50 y e a r s a g o . To t h i s one can add amino a c i d s , a l t h o u g h U n i t e d S t a t e s p r o d u c t i o n i s n o t dominated b y f e r m e n t a t i o n , and v i t a m i n s , and other similar products. In addition, there are other
Hickson; Sucrochemistry ACS Symposium Series; American Chemical Society: Washington, DC, 1977.
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f o o d p r o d u c t s made b y f e r m e n t a t i o n s u c h a s v i n e g a r , s o y s a u c e and y o g u r t w h i c h a l o n e has grown t o a p p r o x i m a t e l y a $250 m i l l i o n b u s i n e s s . A l s o , t h e r e i s t h e enzyme b u s i n e s s , w h i c h has g r o w n t o $50 m i l l i o n o r s o . I t may h a v e p e a k e d h i g h e r t h a n t h a t i n t h e enzyme d e t e r g e n t d a y s , b u t i t i s s t e a d i l y growing. The e n z y m e s f o r w e t c o r n m i l l i n g and h i g h f r u c t o s e c o r n s y r u p p r o d u c t i o n p r o b a b l y h a v e the highest c u r r e n t growth r a t e . In t o t a l , t h e n , t h e r e i s a f e r m e n t a t i o n b u s i n e s s i n t h e U n i t e d S t a t e s t o d a y g r o s s i n g some $8.5 - 9 b i l l i o n . T h a t i s a v e r y s i z a b l e b u s i n e s s and i t i s g r o w i n g . One c o u l d a d d t o t h e c u r r e n t f e r m e n t a t i o n b u s i n e s s , i n t h e U n i t e d S t a t e s , a l l t h e s e c o n d a r y sewage and w a s t e treatment p l a n t s . A l t h o u g h one c a n n o t p u t a v a l u e o n t h e p r o d u c t , a s one c a n f o r t h e o t h e r c o m m e r c i a l f e r m e n t a t i o n s , t h e r e i s a v a l u e , and a h i g h one. B e t w e e n now a n d 1 9 8 5 , some 4,000 o r m o r e c o m m u n i t i e s i n t h e U n i t e d S t a t e s w i l l be b u i l d i n g new s e w a g e d i s p o s a l p l a n t s w i t h secondary b i o l o g i c a l treatment, i n c l u d i n g t h o s e who w i l l h a v e t o u p - g r a d e p r i m a r y plants to secondary p l a n t s . To t h i s t h e r e i s a d d e d i n d u s t r i a l waste treatment business. No a t t e m p t h a s b e e n made t o p u t a d o l l a r v a l u e on j u s t the c o n s t r u c t i o n i n v o l v e d . The s l u d g e p r o d u c e d w i l l be t r e m e n d o u s a n d , a t l e a s t , h a s a f u e l v a l u e , e v e n though the whole o p e r a t i o n i s a net expense t o the t a x payer. The v a l u e i n human h e a l t h t e r m s o f t h i s f e r mentation i s i n c a l c u l a b l e . There does e x i s t a h e a l t h y , t h r i v i n g f e r m e n t a t i o n business i n the United States today. Can one g u e s s where i t i s g o i n g ? A t l e a s t t h e r e c a n be o u t l i n e d some o f t h e p r o s p e c t s , o t h e r t h a n g r o w t h o f a l l t h e above. P r o d u c t i o n o f methane f r o m f e e d l o t w a s t e s by anaerobic fermentation i s just beginning. T h i s i s one waste m a t e r i a l which a l r e a d y i s concentrated geographically. The f i r s t d e m o n s t r a t i o n p l a n t f o r m a k i n g m e t h a n e f r o m u r b a n r e f u s e , a t Pompano B e a c h , F l o r i d a , i s due t o s t a r t up t h i s y e a r . How s u c c e s s f u l t h e s e p r o j e c t s w i l l be i s s t i l l a n o p e n q u e s t i o n . The m a i n factor i n t h e i r favor b a s i c a l l y i s a negative substrate cost. A n o t h e r p r o j e c t f o r b i o p r o d u c t i o n o f methane i n v o l v e s g r o w i n g o f k e l p i n huge b e d s o f f t h e C a l i f o r n i a coast. T h a t one w o u l d seem a b i t f u r t h e r o f f i n t i m e . A g a i n , on t h e e n e r g y s c e n e one i s b e g i n n i n g t o s e e e t h a n o l as a g a s o l i n e a d d i t i v e o r s u p p l e m e n t . I n Nebraska g a s o l i n e i s being promoted, but i t i s i n Braz i l t h a t the p r o d u c t i o n of a l c o h o l f o r motor v e h i c l e
Hickson; Sucrochemistry ACS Symposium Series; American Chemical Society: Washington, DC, 1977.
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use i s a major u n d e r t a k i n g . By t h e m i d - 1 9 8 0 s t h e y h o p e t o g e t p r o d u c t i o n u p t o some 2 b i l l i o n g a l l o n s p e r y e a r , o r a l m o s t 150,000 b a r r e l s p e r day. They a r e p r o j e c t i n g f e r m e n t a t i o n u n i t s o f u p t o 2,000 b b l s / d a y capacity. W h i l e some o f t h i s w i l l b e b a s e d o n t r a d i t i o n a l by-product sources such as molasses, B r a z i l w i l l a l s o u s e whole cane j u i c e s , and i s p l a n n i n g s u b s t a n t i a l c u l t i v a t i o n o f casava, purely f o r ethanol production. S i n g l e c e l l p r o t e i n p r o d u c t i o n (see W e l l s , Chapt e r 22) c o u l d b e b i g , b u t m o r e p r o b a b l y o v e r s e a s r a t h e r than i nthe United S t a t e s . There i s one p o i n t about SCP t h a t m i g h t b e m e n t i o n e d h e r e . F o r e v e r y 100,000 t o n p e r y e a r SCP p l a n t t h a t g o e s i n o v e r s e a s , t h e U.S. l o s e s a p o t e n t i a l f o r soybean o r soybean meal e x p o r t . W i t h o u t a g r i c u l t u r a l e x p o r t s t h e U.S. w o u l d b e h a r d p u t to import almost h a l f i t s crude o i l p l u s r e f i n e d prod u c t s needs. The b a l a n c e o f payments w o u l d d e t e r i o r a t e rapidly. E a c h 1 0 0 , 0 0 0 t o n SCP p l a n t c o s t s t h e U.S. r o u g h l y 1,000,000 b a r r e l s o f c r u d e i n f o r e i g n e x c h a n g e balance. On t h e o t h e r h a n d , SCP p l a n t s c o n v e r s e l y a i d the f o r e i g n n a t i o n s ' balance o f payments. A " s l e e p e r " w o u l d be t h e p r o d u c t i o n o f " s y n t h e t i c " f a t s a n d o i l s f r o m t h e same s o r t o f s u b s t r a t e s u s e d f o r SCP. T h e r e i s much d i s c u s s i o n a b o u t a w o r l d p r o t e i n shortage. A c t u a l l y , the major problem i s a c a l o r i e shortage. I n many n a t i o n s , p r o t e i n s a r e b e i n g u s e d b y t h e human b o d y f o r t h e i r c a l o r i c c o n t e n t , s i m p l y b e c a u s e t h e human i s c a l o r i e s h o r t . The n e t r e s u l t p h y s i c a l l y may seem l i k e a p r o t e i n s h o r t a g e . F i g u r e 3 shows a r e c e n t O r g a n i z a t i o n f o r E c o n o m i c C o o p e r a t i o n a n d D e v e l o p m e n t (OECD) c h a r t o f c a l o r i e availability. T h e FAO s a y s t h e " a v e r a g e " human n e e d s 2,400 c a l o r i e s p e r d a y . Keep i n mind t h a t , i f a n a t i o n , o r c o n t i n e n t , a v e r a g e s 2,400, t h e n h a l f o f t h e population i s starving. D r . M.G. K r i s h n a , o f I n d i a ' s p e t r o p r o t e i n research,estimates t h a t t h eaverage f i g u r e s h o u l d be a t l e a s t 10% above t h e minimum r e q u i r e m e n t t o have 80-90% o f t h e p e o p l e a c h i e v e t h e b a r e minimum. T h a t i s t h e d a s h e d l i n e we h a v e a d d e d a c r o s s t h e OECD chart. The b i g p o p u l a t i o n a r e a s o f t h e w o r l d a r e t h o s e t h a t are c a l o r i e s h o r t . To d a t e t h e s u b s t r a t e s f o r SCP sind f o r f a t s a n d o i l s b y b a c t e r i a l a c t i o n have been p a r a f f i n s , a l c o h o l s , c a r b o h y d r a t e s and methane, p r i m a r i l y . One m i g h t s u g g e s t t h a t s y n t h e s i s g a s , CO p l u s h y d r o g e n , may b e a d d e d i n t h ef u t u r e .
Hickson; Sucrochemistry ACS Symposium Series; American Chemical Society: Washington, DC, 1977.
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