Organic Solvents by Fermentation - ACS Symposium Series (ACS

23 Organic Solvents by Fermentation FRANK WYNN HAYES

Downloaded by GEORGETOWN UNIV on May 6, 2017 | http://pubs.acs.org Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0041.ch023

Roger Williams Technical and Economic Services (U.K.) Inc., London WC1R 4JH, England

The t i t l e s o u n d s s i m p l e e n o u g h , b u t i t r e a l l y i n v o l v e s t a l k i n g about t h e p a s t , t h epresent and t h e f u ture. I n a d d i t i o n , t h eterm " s o l v e n t s " could cover a m u l t i t u d e o f compounds a n d t h i s r e v i e w i s g o i n g t o c o n s i d e r o n l y a few; i n f a c t , t h e f o c u s i s c o n c e r n e d m a i n l y w i t h three - e t h a n o l , butanol and acetone. The o t h e r word i nthe t i t l e i s " f e r m e n t a t i o n " - so t h a t f i x e s the parameters. The d i s c u s s i o n o f t h i s s u b j e c t g o e s b a c k i n t o t h e p a s t b e c a u s e we a r e t a l k i n g o f a n i n d u s t r y t h a t w a s supposed t o have d i e d i n the mid-1950's, b u t never received a burial. I n 1964, J . J . H . H a s t i n g s , i n a n a r t i c l e i nChemistry & Industry s a i d , "...ever since I c a n remember, t h e f e r m e n t a t i o n i n d u s t r y h a s been d y i n g . . . i t i s t h e p h a r m a c i s t who h a s h a l t e d t h e c o f f i n of t h e f e r m e n t a t i o n i n d u s t r y . " By "the pharmacist", o f c o u r s e , H a s t i n g s meant t h e a n t i b i o t i c s i n d u s t r y . These remarks were s i g n i f i c a n t i nremembering the backg r o u n d o f H a s t i n g s , who m o v e d , w i t h D i s t i l l e r s Company, from f e r m e n t a t i o n s o l v e n t s p r o d u c t i o n i n t o a n t i b i o t i c s . F o r 20 y e a r s p r i o r t o t h o s e m i d - 5 0 ' s , t h e r e h a d been an e s t a b l i s h e d , a n d g r o w i n g , i n d u s t r i a l fermentat i o n i n d u s t r y , based m a i n l y on t h eu s e o f b l a c k s t r a p molasses as a s u b s t r a t e . Then, b e g i n n i n g t h e h y d r o c a r b o n a g e , t h e r e came t h e p e t r o c h e m i c a l s , d e r i v e d f r o m 'the e v e r - s o - c h e a p b a r r e l o f c r u d e ' . The b y p r o d u c t s of t h epetroleum i n d u s t r y had u n l i m i t e d promise f o r chemical productions. O l e f i n s and t h e polymers were s t a r t i n g t h e i r boom. E v e r y t h i n g grew b i g g e r , v e r y rapidly. E v e r y o n e t o o k i t t h a t t h e 'cheap b a r r e l o f crude' would, l i k e diamonds, be f o r e v e r . As f o r t h e f e r m e n t a t i o n i n d u s t r y - i t was a c a s e o f " o f f w i t h o l d , a n d o n w i t h t h e new". Hence, t h e statements l i k e t h a t of Hastings. The r e c o r d , h o w e v e r , w o u l d b e n o t q u i t e c o r r e c t i f 313

Hickson; Sucrochemistry ACS Symposium Series; American Chemical Society: Washington, DC, 1977.


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i t was n o t s t a t e d t h a t , j u s t a t t h i s t i m e , t h e r e was a sudden u p s u r g e i n t h e p o p u l a r i t y and use o f m o l a s s e s in stock feeding. T h i s p u t up t h e p r i c e o f b l a c k s t r a p and, c o n c u r r e n t l y , t h e r e were s i g n i f i c a n t r i s e s i n freight rates. A l l o f t h i s t e n d e d t o make t h e i n d u s t r i e s , b a s e d on m o l a s s e s f e r m e n t a t i o n , v e r y u n c e r t a i n about the f u t u r e . B u t , t h e r e s u l t was e q u i v a l e n t t o a n i n e f f i c i e n t j o b o f s t e r i l i z i n g a medium. You k i l l e v e r y t h i n g , o r t h e r e i s a focus of i n f e c t i o n from which growth can spread. T h e r e was a t l e a s t one c e n t r e o f i n d u s t r i a l f e r m e n t a t i o n a c t i v i t y t h a t r e f u s e d t o l i e down, e v e n t h o u g h i t h a d b e e n t o l d i t was d e a d . I t d i d not l i e down f o r t h e v e r y g o o d r e a s o n t h a t i t was m a k i n g p r o fits. What b e t t e r c a u s e c a n y o u h a v e f o r r e f u s i n g that coffin? S o , H a s t i n g s was n o t a b s o l u t e l y c o r r e c t in h i s statement. I t m u s t be i n t e r e s t i n g , a n d c o u l d be i n s t r u c t i v e , t o t a k e a c l o s e r l o o k a t t h a t one o p e r a t i o n t h a t l a s t e d , and a s k o u r s e l v e s "why?". I t was, and i s , a S o u t h A f r i c a n e n t e r p r i s e and t h e r e a s o n t h a t I c a n t a l k a b o u t i t i s t h a t I was p a r t a n d p a r c e l o f i t i n i t s most f o r m a t i v e and e x c i t i n g y e a r s . This undertaking, N a t i o n a l Chemical Products,Ltd., ( N C P ) , a t G e r m i s t o n i n t h e T r a n s v a a l , n o t o n l y was b u c k i n g t h e g e n e r a l s u r r e n d e r t o t h e t i d a l wave o f p e t r o c h e m i c a l s , i t was o f f e n d i n g i n a n o t h e r , a n d e v e n m o r e r e b e l l i o u s manner. I t was n o t f o l l o w i n g t h e w o r s h i p a t t h e a l t a r o f t h e g o d o f LARGE S C A L E . Its substit u t e r e l i g i o n was s i m p l y t h a t o f F U L L U T I L I S A T I O N . By t h i s we mean f u l l u t i l i s a t i o n o f a l l t h e p r o p e r t i e s and c o m p o n e n t s o f t h e f e e d s t o c k and t h e s i d e - p r o ducts that arose i n processing. T h e r e c o u l d be NO EFFLUENT. The p r i n c i p l e s i n v o l v e d w e r e : C l o s e i n t e g r a t i o n o f a l l t h e p r o c e s s e s i n t h e complex; Greatest p o s s i b l e increase of product value; S h a r e d c o s t s f o r l a b o u r and u t i l i t i e s and an umbrella of overheads; The c l o s e s t p o s s i b l e e n e r g y b a l a n c e , w i t h f u l l u t i l i s a t i o n of heat-drop f o r production of power and p r o c e s s steam; and S c a l i n g t h e p r o d u c t i o n t o meet r e q u i r e m e n t s of known a n d p r o f i t a b l e m a r k e t s . B e f o r e d e t a i l i n g w h a t was d o n e , a n d why i t was done, l e t us r e s t a t e o u r c a s e t h a t , n o t o n l y i s t h e r e n o t h i n g new u n d e r t h e s u n , b u t t h a t we s h o u l d be u n w i s e t o t u r n o u r b a c k s on t h e l e s s o n s o f p r a c t i c a l e x p e r i e n c e o f t h e p a s t , e v e n t h o u g h t h o s e d a y s may h a v e lacked today's t e c h n o l o g i c a l f i n e s s e .



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We s h o u l d d i v e r t h e r e , t o a p a r t i c u l a r o u t l e t f o r t h e p h o t o s y n t h e t i c a c t i v i t i e s o f w h i c h we a r e t a l k i n g . P u t t i n g t h e c l o c k b a c k , s t i l l i n t h e e a r l y 1950's i n S o u t h A f r i c a , we w e r e d e b a t i n g s e r i o u s l y t h e r e l a t i v e m e r i t s o f Reppe c h e m i s t r y a n d t h e p o t e n t i a l stemming from a nucleus o f f e r m e n t a t i o n e t h a n o l . Remember t h a t we h a d s e v e r a l t h i n g s g o i n g f o r u s - we h a d t h e f o s s i l r e s e r v e s , i n t h e f o r m o f c h e a p , e a s i l y m i n e d c o a l : we had t h e s u n s h i n e , t h e s o i l , t h e r a i n f a l l t o p r o d u c e good y i e l d s o f s u g a r c a n e , hence e t h a n o l b y f e r m e n t a tion. We w e r e t u r n i n g o u r s i g h t s t o w a r d s t h e new-age things l i k e ethylene and polymers. We a s k e d a d v i c e f r o m t h o s e i n t h e w o r l d ' s c h e m i c a l c e n t r e s - who k n e w . We g o t i t . We w e r e p r o d u c i n g e t h a n o l , b y f e r m e n t a t i o n a t w e l l u n d e r £30/ton ( t h e n , s a y , $ 9 0 / t o n ) . We w e r e t o l d - "So l o n g a s y o u c a n d o t h i s , e t h a n o l m u s t r e m a i n your best source o f ethylene". There were hot debates about the pros and cons o f acetylene v s . e t h a n o l f o r many p u r p o s e s . We h a d a w e l l - b a s e d , e f f i c i e n t c a r b i d e i n d u s t r y , a n d we t h e r e f o r e , c o u l d p r o d u c e i n t e r m e d i a t e s l i k e acetaldehyde and crotonaldehyde by e i t h e r r o u t e . In N a t a l , t h es i t e and centre o f t h esugar indust r y , t h e r e w a s a n o t h e r a c t i v i t y w h i c h we m u s t d e s c r i b e i n some d e t a i l b e c a u s e , n o t o n l y i s i t r e l e v a n t t o t h e subject o f t h i s t a l k but, i t i s very apposite t o t h e b u r n i n g q u e s t i o n s o f today r e g a r d i n g energy sources and l i q u i d f u e l s , p a r t i c u l a r l y f u e l s f o r t h e i n t e r n a l combustion engine. I n , o r a r o u n d , 1 9 3 6 , C.G. S m i t h & C o . , a l e a d i n g s u g a r p r o d u c e r w i t h i t s own e s t a t e s g r o w i n g cane s o u t h o f Durban, went i n t o f e r m e n t a t i o n a l c o h o l p r o d u c t i o n a n d m a r k e t e d a m o t o r s p i r i t t h a t was c a l l e d "Natalité". T h i s c o n t a i n e d some 6 0 % e t h a n o l (Say, 96.5% s t r e n g t h ) a n d 4 0 % b e n z e n e . There were problems. The w a t e r i n t h e i n d u s t r i a l a l c o h o l u s e d i n t h e m i x t u r e c o u l d come o u t o f s o l u t i o n a n d c a u s e p r o b l e m s i n c a r b u r e t i o n and the engine f u e l l i n e s . But, i ns p i t e o f t h i s , i t w o r k e d , i t s o l d , a n d was q u i t e e x t e n s i v e l y u s e d i n f a r m t r a c t o r s , a s w e l l a's h e a v y d u t y t r u c k s a n d ordinary automobiles. The F o r d s o n s a n d the F o r d s o f t h o s e d a y s seemed t o t h r i v e o n i t . Natalité s o l d a t a p r e m i u m o f 3-4 p e n c e a g a l l o n c o m p a r e d w i t h i m p o r t ed p e t r o l ( g a s o l i n e ) , m a i n l y b e c a u s e o f s a v e d d u t y . However, even on t h e s m a l l s c a l e o f i t s p r o d u c t i o n , by the f e r m e n t a t i o n o f b l a c k s t r a p , p l u s benzene from t h e N a t a l c o a l c a r b o n i z a t i o n p l a n t s , i t was c o m p e t i t i t i v e . T h e n , a f t e r W o r l d War I I , t e c h n o l o g y a d v a n c e d . Usines de M e l l e , o f F r a n c e , i n t r o d u c e d t h e i r a z e o t r o p i c d i s t i l l a t i o n p r o c e s s , u s i n g a benzene e n t r a i n e r , and so absol u t e a l c o h o l was a n i n d u s t r i a l p r a c t i c a l i t y . I n 1942, Natalité w a s r e p l a c e d b y " U n i o n S p i r i t " , w h i c h s e l l s



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i n and a r o u n d D u r b a n , N a t a l , t o t h i s day. "Union" i s v e r y i n t e r e s t i n g a n d , i n o u r o p i n i o n , s h o u l d be examined c l o s e l y on a w o r l d - w i d e b a s i s . It is a s t r a i g h t b l e n d o f b e t w e e n 50% t o 59% a b s o l u t e a l c o h o l w i t h a low-octane g a s o l i n e . I n g e t t i n g i t on t h e m a r k e t , t h e C.G. S m i t h G r o u p a d o p t e d a v e r y p r o g r e s s i v e sales policy. They e d u c a t e d t h e m o t o r i n g p u b l i c t o t h e f a c t t h a t t h i s was a n a l c o h o l f u e l a n d i t h a d a d v a n t a g e s , b u t was d i f f e r e n t . I t could a f f e c t the r u b b e r o f t h e f u e l pump d i a p h r a g m a n d s o , f r e e o f charge, a Union S p i r i t mechanic would change the d i a p h r a g m f o r one f a b r i c a t e d f r o m a s y n t h e t i c m a t e r i a l , resistant to alcohol. B e c a u s e o f t h e atom o f oxygen i n the a l c o h o l molecule, the "Union" r e q u i r e d a lower a i r / f u e l r a t i o to give a correct carburetor mixture. T h e r e f o r e , t h e c a r b u r e t o r w o u l d be a d j u s t e d b y f i t t i n g a l a r g e r j e t o r a s m a l l e r choke tube. I n t h i s way e x c e l l e n t f u e l consumption f i g u r e s were o b t a i n e d . U n i o n S p i r i t was n o t t h e o n l y a l c o h o l - c o n t a i n i n g motor f u e l marketed i n South A f r i c a . I n 1934, the S a t m a r Company s t a r t e d m i n i n g t o r b a n i t e o i l s h a l e i n t h e T r a n s v a a l and r e f i n i n g t h e o i l o b t a i n e d f r o m t h e retorting. A t f i r s t t h i s was s i m p l y m i x e d w i t h g a s o l i n e and s o l d i n t h e T r a n s v a a l as Satmar p e t r o l , a g a i n a t a p r i c e premium. I n the mid-40's the c o m p o s i t i o n was c h a n g e d t o a p p r o x i m a t e l y 50% i m p o r t e d c r a c k e d c r u d e s , 25% s p i r i t s f r o m t o r b a n i t e o i l , 25% a b s o l u t e alcohol. The s u p p l i e r o f t h e a l c o h o l , made b y f e r m e n t a t i o n , was N.C.P., a l s o i n t h e T r a n s v a a l , w h o s e o p e r a t i o n s w i l l be d e s c r i b e d i n d e t a i l l a t e r , b u t w e r e centred around the fermentation of b l a c k s t r a p molasses. Satmar enjoyed expanding s a l e s u n t i l the opening o f S a s o l i n 1955. S a s o l , i n t h e Orange F r e e S t a t e , whose a c t i v i t i e s would r e q u i r e a separate paper t o g i v e even a broad o u t l i n e , entered the market w i t h i t s hydrocarbon f u e l s o b t a i n e d by t h e p r e s s u r e g a s i f i c a t i o n o f c o a l , w i t h a F i s c h e r ^ T r o p s c h s y n t h e s i s p a r t l y by A r g e and p a r t l y by K e l l o g g - f l u i d i z e d b e d . Sasol Marketing C o . , was f o r m e d . I t amalgamated the i n t e r e s t s o f the o t h e r s u p p l i e r s a n d s e t up i t s pumps, m a i n l y i n t h e Transvaal, to supply motor s p i r i t c o n t a i n i n g the synt h e s i s products from c o a l , p l u s the d i s t i l l a t e s from i m p o r t e d c r u d e s and n a p h t h a s . The S a s o l m o t o r f u e l , s o l d i n t h e n o r t h e r n F r e e S t a t e and south-western T r a n s v a a l b y S a s o l M a r k e t i n g Co. r e p r e s e n t s o n l y 8% of the t o t a l motor f u e l p r o d u c t i o n of S a s o l , the b a l ance going t o the o i l companies f o r admixture w i t h t h e i r p r o d u c t s a n d d i s t r i b u t i o n t h r o u g h t h e i r own pumps. The d e t a i l s o f t h e S a s o l a c t i v i t i e s h a v e b e e n g i v -



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e n o n l y t o i l l u s t r a t e t h e p o i n t t h a t , u n d e r some c i r cumstances, t h e r e i s ample scope and o p p o r t u n i t y f o r a product/market, such as ethanol/motor s p i r i t where t h e e t h a n o l i s made b y f e r m e n t a t i o n , t o h a v e a n e a s y c o - e x i s t e n c e w i t h motor f u e l s from other indigenous sources. In t h ecase o f Union S p i r i t , s t i l l s o l d today, s t i l l c o n t a i n i n g over 50% f e r m e n t a t i o n e t h a n o l , i t has been c a r r i e d on b y a n o r d i n a r y t r a d i n g company, i n c o m p e t i t i o n w i t h the o t h e r a v a i l a b l e motor s p i r i t s , without any other motive than t h a t o f making p r o f i t s for the shareholders. So o f t e n , when p e o p l e t a l k o f s u b s t i t u t e f u e l s , t h e o n l y c o n c e p t seems t o b e o n e o f COMPLETE r e p l a c e ment; y e t , i f one were c o n s i d e r i n g c r i s e s , s u r e l y i t i s a case o f "every l i t t l e h e l p s " and even 10% h a s some s i g n i f i c a n c e . So now l e t u s r e t u r n t o t h e e x a m p l e o f a d i v e r s i f i e d , i n t e g r a t e d fermentation complex, w i t h a mainstream production o f s o l v e n t s , that has proved a commercial p r o p o s i t i o n i n s p i t e o f t h e coming o f t h e "camel t r a i n , c a r r y i n g i t s b a r r e l s o f b l a c k g o l d ! " At South A f r i c a ' s N a t i o n a l Chemical Products, t h e p r o d u c t i o n f l o w s h e e t showed t h e f o l l o w i n g m a i n pathways : Intermediates

Products

Blackstrap molasses Coal Water Cornsteep l i q u o r Ammonia Lime

Ethanol Butanol Acetone Carbon d i o x i d e Hydrogen Acetaldehyde

Sulphuric

Acetic

Absolute alcohol Industrial spirit Potable s p i r i t Acetone Butanol Fusel oils (amyl a l c o h o l ) S p i r i t vinegar (10%) Liquid C0

Raw

Materials

acid

Miscellaneous Chemicals

acid

Crotonaldehyde

2

Dry i c e Acetic acid Ethyl & Butyl acetates Cellulose paint thinners Animal feed supplements Froth flotation reagents The

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o n l y a s b e i n g t y p i c a l , i s t h e c o - e x i s t e n c e a n d comp l e t e interdependence o f a l l these productions. There were two main f e r m e n t a t i o n s ( s e e F i g u r e 1) - a n e t h a n o l f e r m e n t a t i o n u s i n g t h e u s u a l S. c e r e v i s i a e ; NOT r u n continuously but with the large batch fermenters being "set" i n t h r e e separate stages so as t o even o u t t h e CO2 e v o l u t i o n f o r t h e b e n e f i t o f t h e D r y I c e P l a n t . I n p r a c t i c e , i t proved a good system. The o t h e r f e r m e n t a t i o n , using C I . acetobutylicum, produced butanol, a c e t o n e a n d e t h a n o l i n t h e p r o p o r t i o n s o f 6:3:1, w i t h CO2 a n d H 2 a s t h e g a s e o u s p r o d u c t s . The m i x e d g a s e s went o n t o an a b s o r p t i o n p l a n t w h e r e t h e C 0 was removed, t o be added t o t h a t f r o m t h e e t h a n o l f e r m e n t a t i o n f o r t h e D r y I c e p l a n t a n d t h e s e p a r a t e d H was used i n an a s s o c i a t e d p h t h a l i c a n h y d r i d e p l a n t . In t h e e a r l i e r o p e r a t i o n s , t h e spent wash from b o t h e t h a n o l a n d b u t a n o l f e r m e n t a t i o n s was e v a p o r a t e d t o b e t w e e n 40 a n d 4 5 % s o l i d s a n d t h e n i n c i n e r a t e d i n a purpose-developed, spray dryer-cum-incinerator i n w h i c h t h e o r g a n i c m a t t e r s u p p o r t e d i t s own combustion, on much t h e same p r i n c i p l e a s a b l a c k l i q u o r f u r n a c e , y i e l d i n g a n a s h w i t h a b o u t 3 5 % K 0 c o n t e n t , w h i c h was s o l d t o t h e f e r t i l i z e r compounders. T h e n i t was f o u n d t h a t a b e t t e r r e t u r n c o u l d be o b t a i n e d by s e p a r a t i n g t h e two d i f f e r e n t t y p e s o f spent wash from t h e e t h a n o l and t h e b u t a n o l f e r m e n t a t i o n s . The b u t a n o l f e r m e n t a t i o n r e s i d u e s c o n t a i n e d v i t a m i n s o f t h e B group, so this material, after concentration i n a multiple effect e v a p o r a t o r , was d r i e d o n d o u b l e - d r u m d r y e r s t o y i e l d a d r y powder w i t h t h e f o l l o w i n g i n t e r e s t i n g c o m p o s i t i o n :


2

2

2

Moisture Loss on i g n i t i o n Protein Riboflavin Pantothenic acid Choline Nicotinic acid Pyridoxine B 12

3.5 % ( b y w t ) 63.2 11.0 45 y/g 175 3200 89 51 0.156 "

T h i s was i m m e d i a t e l y s a l e a b l e t o f e e d i n g - s t u f f s comp o u n d e r s a t a p r i c e t h a t s t a r t e d t o make t h e m a t e r i a l a p r o d u c t i n i t s own r i g h t , n o t j u s t a n e f f l u e n t d i s p o s a l credit. I n t h e meantime, t h e ethanol-spent-wash-ash c o n t i n u e d t o s e l l as a potash f e r t i l i z e r . The n e x t d e v e l o p m e n t was t h e d i s c o v e r y , a f t e r much b i o l o g i c a l t e s t i n g a n d l o n g - t e r m f e e d i n g t r i a l s , t h a t t h e comb i n e d , spray d r i e d r e s i d u e s from both f e r m e n t a t i o n s , i f i n c o r p o r a t e d i n t h e r a t i o n s o f g r a z i n g animals, had a


HAYES


Water

MOLASSES

Nutrients

CO 2L

TO

Ethanol Fermentation

CO 2 + H

-ut

H for Hydrogénation Ethanol Distillation

Liquid & S o l i d C02

s

"7F Butanol Fermentation

2


319

/ /IV

Fusel Oils

Butanol kcetone

Distillation Ethanol Evaporation & Drying

S.C.P. Fermentation

Animal Feed Supplements Industrial

Fractionation and Rectification

Potable

Absolute Alcohol

Spirit

Acetaldehyde

1

^

Aldol

Spirit

Spirit

Vinegar

f-^.Crotonaldehyde

Bu t a n o l

>

Triethoxybutane and s i m i l a r Surfactants

Ethanol

Acetic a c i d & A c e t i c anhydride

}

Esters A l d e h y d e ammonia.. Pa r a l d ehy d e/L^e t a l d ehy d e/

Figure 1


->


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SUCROCHEMISTRY

marked b e n e f i c i a l e f f e c t on t h e m i c r o f l o r a o f t h e rumen, enabling the animal t o u t i l i z e s u c c e s s f u l l y , q u i t e i n f e r i o r types o f s t r a w , g r a s s and o t h e r c e l l u l o s i c materials. T h e name o f " R u m a v i t e " w a s g i v e n t o t h i s m a t e r i a l and i t s o l d on a world-wide b a s i s . This, again, i s the story of the successful prod u c t i o n o f SOLVENTS b y f e r m e n t a t i o n . Some o f t h e e t h a n o l o u t p u t was c o n v e r t e d t o acetaldehyde f o r c a p t i v e use. A c e t i c a c i d was made f o r t h e p r o d u c t i o n o f e s t e r s and a l s o f o r c o n v e r s i o n t o c r o t o n a l d e h y d e w h i c h a g a i n was c o n d e n s e d w i t h e t h a n o l t o make t r i e t h o x y b u t a n e , o n e o f a w h o l e r a n g e o f a l k oxy compounds t h a t w e r e p a t e n t e d f o r u s e a s f r o t h f l o t a t i o n reagents, p a r t i c u l a r l y s u c c e s s f u l i n copper and u r a n i u m r e c o v e r y . And so t h e s t o r y c o n t i n u e s , w i t h each product a l o g i c a l p a r t o f t h e sequence, w i t h a c a r e f u l l y i n v e s t i g a t e d market, w i t h a h e l p f u l spread to t h e f i x e d charges and g e n e r a l overheads. I n other words, each being a s u c c e s s f u l p a r t o f t h e whole b u t undoubtedly, i fseparated and expected t o stand as a p r o d u c t i o n o n i t s own, t o o s m a l l t o s u r v i v e . Now w h a t o f t h e f u t u r e ? I s there a prospect f o r the r e - i n s t i t u t i o n o f fermentation i n t h e production o f solvents? The a n s w e r s t o t h e s e v e r y " l e a d i n g " q u e s t i o n s a r e : 1. Study and use t h e e x p e r i e n c e o f t h e i n d u s t r i a l f e r m e n t a t i o n s t h a t worked b e f o r e t h e p e t r o c h e m i c a l age; more p a r t i c u l a r l y , t h o s e w h i c h r e m a i n e d a l i v e t h r o u g h t h e f a c t t h a t t h e y made p r o f i t s . 2. On t h e f o u n d a t i o n o f 1. a p p l y a l l t h e b e n e f i t s p o s s i b l e b y r e a s o n o f new t e c h n o l o g i e s a n d t e c h n i q u e s now a v a i l a b l e t o u s ; w i t h t h e c o l l a b o r a t i o n o f t h e d i s c i p l i n e s of the geneticist, the molecular b i o l o g i s t , the b i o c h e m i s t , t h e m i c r o b i o l o g i s t and t h e b i o c h e m i c a l engineer. Now, we c a n m a n i p u l a t e t h e m i c r o o r g a n i s m s of t h e s p e c i f i c c u l t u r e t h a t a r e our working c a t a l y s t s , t h e i r m e t a b o l i c p a t h w a y s , and t h e enzymes t h e y p r o d u c e . By b i o g e n e t i c m a n i p u l a t i o n s t h e y c a n b e made t o d o o u r b i d d i n g ; we d o n o t s i m p l y h a v e t o t a k e t h e b e h a v i o u r p a t t e r n o f an organism under one s e t o f c i r c u m s t a n c e s a s b e i n g f i x e d a n d i n v i o l a b l e :we c a n a l t e r t h e o r g a n i s m to s u i t t h e d e s i r e d product, t h e a v a i l a b l e s u b s t r a t e , the fermentation c o n d i t i o n s . 3. I f we t h i n k i n t e r m s o f " L a r g e - S c a l e " f o r t h e p r o d u c t i o n o f s o l v e n t s by f e r m e n t a t i o n then t h e most i m p o r t a n t f a c t o r i s t h e form, source and c o s t o f t h e substrate carbon. I n o u r o p i n i o n t h e r e c a n be o n l y one s o u n d b a s i s f o r t h i s r e n e w a b l e r a w m a t e r i a l s u p p l y : i t must be p u r p o s e - g r o w n . 4. I f we t h i n k i n t e r m s o f a f a i r l y m o d e s t s t a r t a n d


23.

HAYES


321

a s t e a d y a n d p l a n n e d s c a l e - u p , t h e n we l o o k v e r y c l o s e ly indeed a t t h e e x p e r i e n c e o f t h e p a s t where d i v e r s i f i c a t i o n , i n t e g r a t i o n and f u l l u t i l i s a t i o n o f every c o n s t i t u e n t o f t h e f e e d s t o c k and o f every i n t e r m e d i a t e , are e x p l o r e d . 5. We c a n n o t t a l k o f a r e t u r n t o " r e n e w a b l e s o u r c e s " a n d f e r m e n t a t i o n a s t h e c h o s e n r o u t e u n l e s s we k e e p a l ways i n mind t h e E n e r g y B a l a n c e . This i sthe key. I n t h e g r o w t h o f c r o p s f o r a s p e c i f i c p u r p o s e we w i l l be u s i n g s o l a r e n e r g y , p h o t o s y n t h e s i s , t h e G r e e n L e a f COMMERCIALLY. I f we s h o u l d , f o r i n s t a n c e , g r o w m o r e s u g a r c a n e , we m u s t u s e e v e r y g r a m o f e v e r y s t i c k t o t h e maximum e f f e c t . I f we b u r n a l l , o r some o f , t h e r e s i d u a l f i b r e and c e l l u l o s i c p o r t i o n t o p r o v i d e t h e h e a t a n d p o w e r f o r t h e p r o c e s s , i t m u s t b e b e c a u s e we have no o t h e r f u e l t h a t i s a v a i l a b l e a n d c h e a p e r , t o burn. I f there i s a s u i t a b l e s u b s t i t u t e f u e l , then we u s e o u r f i b r e f r o m t h e c a n e a s a s o u r c e o f p e n t o s e s and h e x o s e s . We u s e t h e s u g a r s a v a i l a b l e t o u s according t o t h e product market i n d i c a t i o n s . 6. We w i l l h a v e t o g e n e r a t e s t e a m a t h i g h p r e s s u r e and u t i l i s e t h e h e a t d r o p t h r o u g h a b a c k - p r e s s u r e o r p a s s - o u t t u r b i n e t o g e n e r a t e power and t o s u p p l y t h e low-pressure p r o c e s s steam. No l o s s o f l a t e n t h e a t can be a f f o r d e d o r t o l e r a t e d . A l l t h e a b o v e p o i n t s , a n d s o many m o r e , b e l o n g t o t h a t f a s c i n a t i n g s u b j e c t "FERMENTATION". There a r e t e c h n o l o g i c a l p r o j e c t i o n s o f t h e new l o o k i n f e r m e n t a t i o n e m b o d y i n g a l l t h e f a c t o r s we h a v e b e e n d i s c u s s i n g and more b e s i d e s . A model d e s i g n c a n produce s o l v e n t s on a l a r g e s c a l e . I t involves continuous fermentation, employing t h e r m o p h i l i c organisms. Distillation requirements a r e reduced by a very s u b s t a n t i a l margin. A l l components o f t h e s u b s t r a t e a r e u t i l i z e d e x c e p t t h e water.


f

Abstract Do the escalated prices for a barrel of crude oil, and the visible end of fossil supplies of energy,justify a new look at fermentation for bulk chemicals? They do, but the examination must be thorough, factual and not simply wordy. The feedstocks are important, but just as critical is the energy balance. So too are the new tools available to the fermentologist in biogenetics, biochemistry, and biochemical engineering. Fermentation technology has not stood still. But, renewable sources do not necessarily mean economically viable sources. Market surveys plus past experience can help us in our assessments. In the latter cate—


322

SUCROCHEMISTRY gory, experience in both South Africa and Australia is valuable. The former is somewhat unique because of its pioneering both in the large-scale use of high concentrations of ethanol in motor fuel and the later development of " o i l from coal" by Fischer-Tropsch, with products and side products that competed with its local fermentation production of ethanol, butanol, and acetone.


Biographic Notes Frank W. Hayes, FRIC, FI Chem. Eng., M.S.A. Chem. Ing.,V.P. Chem. and Eng. Economic Consultant. Educated at Natal Technical Coll.and Natal Univ.Coll. Research chemist at South African Sugar Assoc., Expt. Station and Chief Chem. Huletts S.A. Refiners Ltd., then Tech.Dir. of National Chemical Products Ltd., of South Africa, specializing in organic chemicals by fermentation; moved to the United Kingdom and the Distiller's Co., Ltd., Humphreys and Glasgow, Ltd., thence to Roger Williams Technical and Economic Services (U.K.) Inc. 37 Sussex Square, Hyde Park, London, W.2. England.



Discussion

P r o f e s s o r H o u g h ; Why i s p e n t a e r y t h r i t o l utilized? Is i t too expensive?

not

Professor Frisch; I n d e e d , i t i s one o f t h e i m p o r t a n t m a t e r i a l s f o r r i g i d u r e t h a n e foams; b e i n g used as t h e p o l y o l . I t i s u s e d m o s t l y f o r r i g i d foam applications. Some o f i t i s a l s o b e i n g u s e d i n t h e urethane c o a t i n g a r e a i n the form o f p o l y o l s . The c o s t s o f t h e s e p o l y o l s a r e a b o u t 45 t o 46C a p o u n d . T h e y command m o r e o r l e s s a p r e m i u m p r i c e a s c o m p a r e d to sucrose or s o r b i t o l - b a s e d p o l y o l s . Dr. F u z e s i ; The c y c l i c s t r u c t u r e - w h i c h i s m i s s i n g i n p e n t a e r y t h r i t o l and w h i c h i s p r e s e n t i n s u c r o s e - i s v e r y i m p o r t a n t i n t h e r i g i d u r e t h a n e foam area. There the p e n t a e r y t h r i t o l - b a s e d p o l y o l a l o n e , j u s t d o e s n o t h a v e g o o d f o a m p r o p e r t i e s a n d s h o u l d be blended w i t h something e l s e . I t s h o u l d be b l e n d e d w i t h sucrose-based p o l y o l . Question; Does s u c r o s e have an a d v a n t a g e o v e r o l i g o - s a c c h a r i d e s w h i c h have a h i g h m o l e c u l a r w e i g h t ? Dr. F u z e s i ; I t i s more d i f f i c u l t t o h a n d l e t h e oligosaccharides. Another f a c t o r i s the a v a i l a b i l i t y of s u c r o s e . Mono- o r d i s a c c h a r i d e s - l i k e t h e d e x t r o s e and s u c r o s e b a s e d s y s t e m s , a r e w e l l d e v e l o p e d and I t h i n k t h o s e a r e most s u i t a b l e f o r use i n r i g i d foams. f

P r o f e s s o r Hough; advantages. Dr. F u z e s i ; Question;

T h e r e f o r e , s u c r o s e h a s many

Y e s , many, many Do

you

advantages.

see any n o t i c e a b l e

difference

323


324

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between t h e p r o d u c t s from s o r b i t o l o r l a c t i t o l - t y p e polyols versus sucrose which i s not a t t r i b u t a b l e t o the b i c y c l i c character versus the l i n e a r polyol? Professor Frisch; I t h i n k i t was m e n t i o n e d t h a t the b i c y c l i c s t r u c t u r e g i v e s i t b e t t e r d i m e n s i o n a l s t a b i l i t y and b e t t e r h u m i d i t y r e s i s t a n c e , w h i c h i s what you need i n a r i g i d foam. T h o s e who b u y r i g i d f o a m s , probably are buying i n s u l a t i o n value. I f you do n o t have t h o s e two p r o p e r t i e s , y o u w i l l n o t be a b l e t o keep your i n s u l a t i o n value. The s t r u c t u r e i s v e r y i m p o r tant f o r humidity aging. The o n l y p l a c e I c a n t h i n k o f where y o u p u t a r i g i d u r e t h a n e foam t h a t y o u do not have h u m i d i t y i s i n t h e f r e e z e r s e c t i o n o f t h e r e f r i g e r a t o r c a b i n e t , i n between t h e i n n e r l i n e r and t h e outer l i n e r .


Organic Solvents by Fermentation - ACS Symposium Series (ACS

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