[acs symposium series] sucrochemistry volume 41 || production of industrially important gums with...

21

Production of Industrially Important Gums with Particular Reference to Xanthan Gum and Microbial Alginate

CHRISTOPHER J. LAWSON Tate & Lyle Ltd., Group R & D, P.O. Box 68, Reading, Berks, RG6 2BX, England

The p r o d u c t i o n o f p o l y s a c c h a r i d e gums by f e r m e n t a t i o n has been d e s c r i b e d by some o f t h e more o p t i m i s t i c m i c r o b i a l t e c h n o l o g i s t s as t h e n e x t m a j o r f e r m e n t a t i o n a r e a . I t now i s g a i n i n g t r e a t m e n t i n p u b l i c and p r i v a t e m e e t i n g s s i m i l a r t o t h a t o f f e r e d t o s i n g l e c e l l p r o t e i n some y e a r s ago. T h i s o p t i m i s m i s b a s e d on t h e undoubted s u c c e s s o f t h e m a j o r p r o d u c t i n t h i s a r e a , x a n t h a n gum, w h i c h has r a i s e d t h e t a n t a l i s i n g p r o s p e c t o f a whole r a n g e o f m i c r o b i a l gums w h i c h c o u l d n o t o n l y r e f l e c t and improve upon t h e a v a i l a b l e p l a n t gums, b u t a l s o i n t r o d u c e n o v e l p r o p e r t i e s f o r e x p l o i t a t i o n i n e x i s t i n g and as y e t u n d e v e l o p e d a p p l i c a t i o n s . A bout a do z e n m a j o r companies a r e t h o u g h t t o be c o n d u c t i n g s u b s t a n t i a l r e s e a r c h and devel o p m e n t programmes i n t o t h e p r o d u c t i o n o f m i c r o b i a l p o l y s a c c h a r i d e s ; some o f them a l r e a d y a r e i n t h e f e r m e n t a t i o n i n d u s t r y , b u t o t h e r s , l i k e T a t e and L y l e and H e r c u l e s , a r e newcomers t o t h i s t e c h n o l o g y . D e s p i t e t h i s heavy r e s e a r c h and de v e l o p m e n t e f f o r t w h i c h , i n some i n s t a n c e s has a h i s t o r y o f a t l e a s t a d e c a d e , t h e s t a t e o r a t l e a s t p u b l i c knowledge o f t h e t e c h n o l o g y as j u d g e d f r o m t h e p a t e n t and s c i e n t i f i c l i t e r a t u r e , i s l o w , t o say t h e l e a s t . T h e r e i s l i t t l e l i t e r a t u r e on t h e p r o d u c t i o n t e c h n o l o g i e s u s e d by i n d u s t r y . Academic m i c r o b i o l o g y , f o r t h e most p a r t , has i g n o r e d t h e phys i o l o g y o f e x o c e l l u l a r p o l y s a c c h a r i d e s y n t h e s i s and e x c r e t i o n . The p h y s i o l o g y o f p o l y s a c c h a r i d e s y n t h e s i s has been s t u d i e d as a b a s i s f o r d e v e l o p i n g p r o d u c t i o n p r o c e s s e s . A number o f t h e r e s u l t s o b t a i n e d on m i c r o b i a l a l g i n a t e i n t h e T a t e and L y l e l a b o r a t o r i e s w i l l be d i s c u s s e d . As a b r i e f i n t r o d u c t i o n t o m i c r o b i a l gum p r o d u c t i o n , i t w i l l be u s e f u l t o c o n t e m p l a t e a number o f more g e n e r a l q u e s t i o n s w h i c h w o u l d be po s e d by an i n d i v i d u a l o r gr o u p o f i n d i v i d u a l s c o n s i d e r i n g t h i s f i e l d f o r p o s s i b l e e x p l o i t a t i o n .

282

Dow

nloa

ded

by U

NIV

OF

MIS

SOU

RI

CO

LU

MB

IA o

n A

pril

22, 2

013

| http

://pu

bs.a

cs.o

rg

Pub

licat

ion

Dat

e: J

une

1, 1

977

| doi

: 10.

1021

/bk-

1977

-004

1.ch

021

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

21. LAwsoN Industrially Important Gums 283

1. What a r e b i o p o l y m e r s o f i n d u s t r i a l s i g n i f i c a n c e ?

2. Why s h o u l d s u g a r companies show any i n t e r e s t ? 3. What i s t h e c o m m e r c i a l s t a t u s o f m i c r o b i a l

gums? 4« What a r e t h e p r o p e r t i e s o f i n t e r e s t ? 5. What a d v a n t a g e s has f e r m e n t a t i o n t o o f f e r ? 6. What d i s a d v a n t a g e s does f e r m e n t a t i o n have?

From t h e p o i n t o f v i e w o f c o m m e r c i a l u s e f u l n e s s , m i c r o b i a l p o l y s a c c h a r i d e s a r e f o u n d as s l i m y o r g e l a t i n o u s m a t e r i a l s s e c r e t e d i n t o t h e aqueous e n v i r o n m e n t upon w h i c h a r e grown many b a c t e r i a , f u n g i and y e a s t s . The r e a s o n why t h i s g r o u p o f compounds has r e c e i v e d a t t e n t i o n i s c o n n e c t e d w i t h t h e r h e o l o g i c a l and g e l -f o r m i n g p r o p e r t i e s w h i c h t h e y show, d e f i n e d by c o m p a r i son w i t h t h e w e l l - k n o w n , i n d u s t r i a l gums fr o m p l a n t s o u r c e s . I n T a b l e I t h e m a j o r a r e a s o f gum c l a s s i f i c a t i o n a r e p r e s e n t e d , showing c o m p a r i s o n s o f b o t h p l a n t and m i c r o b i a l gums.

The i n t e r e s t o f T a t e and L y l e i n m i c r o b i a l gums was s t i m u l a t e d b y t h e e f f e c t i v e i n c r e a s e i n v a l u e w h i c h m i g h t be g i v e n t o s u c r o s e i f u s e d as a f e r m e n t a t i o n s u b s t i t u t e . G e n e r a l l y , gums can be c l a s s e d as h i g h T a b l e I .

C l a s s i f i c a t i o n o f W a t e r S o l u b l e P o l y s a c c h a r i d e s

O r i g i n

(i) U n m o d i f i e d G u m s

' t rees seeds

p l a n t s

microorganisms

s e a w e e d s

c e r e a l s tubers

^ c i t r u s f ru i t s

b a c t e r i a

p l a n t s

microorganisms

( i i ) M o d i f i e d G u m s

^ t r e e s grasses c o t t o n s c e r e a l s tubers s e a w e e d s

^ c i t r u s f ru i t s b a c t e r i a

- L

E x a m p l e s

gum a r a b ï c [l o c u s t b e a n g u m g u a r g u m a g a r a l g i n a t e

L c a r r a g e e n a n c o r n s t a r c h p o t a t o s t a r c h p e c t i n

C d e x t r a n x a n t h a n gum

[c a r b o x y m e thy I c e 11 u i ose m e t h y l c e l l u l o s e h y d r o x y m e t h y l c e l l u l o s e

r d e x t r i n s *-ca rboxymethy l s t a r c h

p r o p y l e n e g l y c o l a l g i n a t e l o w m e t h o x y p e c t i n D . E . A . E . d e x t r a n ( D i e t h y l a m i n o e t h y l )

Dow

nloa

ded

by U

NIV

OF

MIS

SOU

RI

CO

LU

MB

IA o

n A

pril

22, 2

013

| http

://pu

bs.a

cs.o

rg

Pub

licat

ion

Dat

e: J

une

1, 1

977

| doi

: 10.

1021

/bk-

1977

-004

1.ch

021


284 SUCROCHEMISTRY

v a l u e c h e m i c a l s , and i t was c o n s i d e r e d t h a t t h e i r p r o d u c t i o n by f e r m e n t a t i o n p r o c e s s e s c o u l d l e a d t o r e t u r n s on c a p i t a l employed b e t t e r t h a n t h o s e o b t a i n e d , f o r example, by s t r a i g h t f i n a n c i a l i n v e s t m e n t . There a l s o was a n a t u r a l a t t r a c t i o n t o w a r d s a p o t e n t i a l i n v o l v e ment w i t h t h e new a r e a o f d i v e r s i f i c a t i o n , w h i c h p r o d u c t i o n o f m i c r o b i a l gums w o u l d o f f e r . G l u c o s e and g l u c o s e s y r u p s may be o b t a i n e d more c h e a p l y t h a n r e f i n e d cane s u g a r a n d , i n any l o g i c a l p r o c e s s d e v e l o p ment e x e r c i s e , i t w o u l d be n e c e s s a r y t o acknowledge t h i s . F o r c e r t a i n p o l y s a c c h a r i d e f e r m e n t a t i o n s , howe v e r , t h e use o f raw s u g a r , r e f i n i n g s y r u p s o r m o l a s s e s may be c o n t e m p l a t e d s u b s t a n t i a l l y i m p r o v i n g t h e econom i c s i n c o m p a r i s o n w i t h g l u c o s e . A l s o , many s u g a r companies have s t r o n g i n t r i n s i c i n t e r e s t s i n c a r b o h y d r a t e s o t h e r t h a n s u c r o s e . A g a i n , t h i s i s a p o s s i b l e r e a s o n f o r an i n t e r e s t i n f e r m e n t a t i o n s u b s t r a t e s o t h e r t h a n s u c r o s e . One o b v i o u s d i s a d v a n t a g e f o r a s u g a r company c o n t e m p l a t i n g t h e m a n u f a c t u r e o f m i c r o b i a l gums i s t h e p r o b a b l e l a c k o f b o t h a p p l i c a t i o n s know-how and m a r k e t i n g e x p e r t i s e . One o f t h e main m o t i v a t i n g r e a s o n s f o r T a t e and L y l e ' s e n t h u s i a s m a t a j o i n t v e n t u r e w i t h a company l i k e H e r c u l e s , was i n t h e s t r e n g t h t o be g a i n e d f r o m an o r g a n i s a t i o n a l r e a d y m a r k e t i n g gums.

A v a s t number o f m i c r o o r g a n i s m s p r o d u c e e x o c e l l u -l a r p o l y s a c c h a r i d e s , and many p u b l i c a t i o n s have a p p e a r e d , i n w h i c h t h e y a r e d e s c r i b e d . The m a j o r i t y , howe v e r , have n o t been e x p l o i t e d c o m m e r c i a l l y . I n T a b l e I I some p o l y s a c c h a r i d e - p r o d u c i n g m i c r o o r g a n i s m s a r e shown t o g i v e an i d e a o f t h e w i d e o c c u r a n c e o f t h e p o l y s a c c h a r i d e p r o d u c e r s . I n T a b l e I I I a r e l i s t e d t h o s e gums w h i c h a p p e a r t o be t h e most advanced i n terms o f t h e i r c o m m e r c i a l d e v e l o p m e n t . T h i s demons t r a t e s t h e c o m m e r c i a l s t a t u s o f t h e gums and g i v e s an i n d i c a t i o n o f p o s s i b l e f u t u r e t r e n d s . To g i v e an i d e a o f t h e s o r t o f p r o d u c t i o n volumes o f m i c r o b i a l gums, i t has been e s t i m a t e d t h a t t h e p r o d u c t i o n o f x a n t h a n gum by a l l m a n u f a c t u r e r s amounted t o some 6,000 t o n n e s i n 1975. T a b l e I V p r e s e n t s f o r c o m p a r i son t h e c o n s u m p t i o n o f gums i n t h e U n i t e d S t a t e s i n 1973. P r o d u c t i o n c o s t s f o r m i c r o b i a l gums a r e v e r y h i g h , m a i n l y due t o t h e h i g h c o s t o f p l a n t . A number o f r e a s o n s f o r t h i s a r e g i v e n l a t e r . K e l c o , f o r i n s t a n c e , has announced t h a t t h e i r new p l a n t f o r x a n t h a n gum p r o d u c t i o n i n Oklahoma, w i l l c o s t $35 m i l l i o n . The p r i c e s c h a r g e d r e f l e c t t h i s h i g h p r o d u c t i o n c o s t and t h e r e f o r e , i t i s n o t s u r p r i s i n g t h a t t h e p r i c e o f x a n t h a n r a n g e s f r o m $3.5 p e r l b t o $4 p e r l b , d e p e n d i n g upon g r a d e .

Dow

nloa

ded

by U

NIV

OF

MIS

SOU

RI

CO

LU

MB

IA o

n A

pril

22, 2

013

| http

://pu

bs.a

cs.o

rg

Pub

licat

ion

Dat

e: J

une

1, 1

977

| doi

: 10.

1021

/bk-

1977

-004

1.ch

021



T a b l e I I . S o m e P o l y s a c c h a r i d e - P r o d u c i n g M i c r o o r g a n i s m s

G r a m P o s i t i v e B a c t e r i a

B a c i l l u s s p p .

L e u c o n o s t o c s p p .

S t r e p t o c o c c u s m u t a n s

S t r e p t o c o c c u s s p p .

G r a m n e g a t i v e B a c t e r i a

A z o t o b a c t e r si

R h i z o b i u m £p_.

SD£.

Y e a s t s

R h o d o t o r u l a s p p . P i c h i a s p p .

P a c h y s o l e n t a n n o p h i l u s L i p o m i c e s s p p . H a n s e n u l a c a p s u l a t a H . H o l s t i i

C r y p t o _sp£.

E s c h e r i c h i a c o l i

K l e b s i e l l a a e r o g e n e s

A c e t o b a c t e r x y l i n u m

A r t h r o b a c t e r v i s c o s u s

P s e u d o m o n a s a e r u g i n o s a

X a n t h o m o n a s c a m p e s t r i s

X . p h a s e o l i

A c h r o m o b a c t e r s p p .

A l c a l i g e n e s f a e c a l is v a r . m y x o g e n e s

A g r o b a c t e r i u m s p p .

E r w i n i a s p p .

S p h a e r o t i l u s m u t a n s

T o r u l o p s i s m o l i s c h i a n a

T . P i n u s

A u r e o b a s i d i u m p u l l u l o n s

O t h e r F u n g i

P é n i c i l l i u m s p p .

T r e m e l l a m e s e n t a r i a

T a b l e V g i v e s an i n d i c a t i o n o f t h e t y p e o f p r o c e s s e i t h e r b e i n g o p e r a t e d o r i n de v e l o p m e n t . I t i s t h o u g h t t h a t a l l c o m m e r c i a l i s e d p r o c e s s e s , a t t h e mome n t , a r e b a t c h , and a l l s u b s t r a t e s a r e c a r b o h y d r a t e s , m o s t l y b a s e d on g l u c o s e o r s u c r o s e .

I n t h e s e l e c t i o n o f m i c r o b i a l gums f o r c o m m e r c i a l e x p l o i t a t i o n , i n e v i t a b l y t h e c o n c l u s i o n i s r e a c h e d , t h a t , f o r a gum t o be s u c c e s s f u l , i t must have some u n i q u e p h y s i c a l p r o p e r t y . As a l r e a d y m e n t i o n e d , p r o d u c t i o n c o s t s a r e h i g h a nd, i t i s u n r e a l i s t i c t o c o n t e m p l a t e d e v e l o p i n g gum systems w h i c h show n o n - s p e c i f i c t h i c k e n i n g and s u s p e n d i n g p r o p e r t i e s . I n T a b l e V I a r e l i s t e d some p o l y s a c c h a r i d e s , b o t h p l a n t and m i c r o b i a l , i d e n t i f y i n g t h e p h y s i c a l p r o p e r t i e s w h i c h a r e u n i q u e , and u s e s w h i c h a r e s p e c i f i c and n o t e a s i l y c o p i e d by o t h e r gums.

B o t h t h e a d v a n t a g e s and d i s a d v a n t a g e s o f t h e f e r m e n t a t i o n a p p r o a c h t o p o l y s a c c h a r i d e p r o d u c t i o n now w i l l be examined ( T a b l e V I I ) . A d v a n t a g e s o f f e r m e n t a t i o n o v e r t r a d i t i o n a l methods a r e f i r s t l y i n medium p r e p a r a t i o n . The raw m a t e r i a l s s u c h as c a r b o h y d r a t e s u b s t r a t e s , n i t r o g e n s o u r c e s and i n o r g a n i c s a l t s n o r m a l l y a r e r e a d i l y a v a i l a b l e and, i n many f e r m e n t a t i o n s , i t

Dow

nloa

ded

by U

NIV

OF

MIS

SOU

RI

CO

LU

MB

IA o

n A

pril

22, 2

013

| http

://pu

bs.a

cs.o

rg

Pub

licat

ion

Dat

e: J

une

1, 1

977

| doi

: 10.

1021

/bk-

1977

-004

1.ch

021


286 SUCROCHEMISTRY

T a b l e I I I . M i c r o b i a l P o l y s a c c h a r i d e s o f C o m m e r c i a l I m p o r t a n c e ( C o m m e r c i a l I n fo rmat ion )

T r a d e N a m e C o m p a n y I n v o l v e d N a m e

D e x t r a n

X a n t h a n G u m

P u l l u l a n

E r w i n i a

E x o p o l y s a c c h a r i d e

S c l e r o g l u c a n

S t a t e o f D e v e l o p m e n t

P r e sen t - In p r o d u c t i o n F u t u r e - S t a t i c

P r esen t - In p r o d u c t i o n F u t u r e - E x p a n d i n g

P r e sen t - In d e v e l o p m e n t F u t u r e - C o m m e r c i a l i s a t i o n

a n n o u n c e d

P r e sen t - In d e v e l o p m e n t F u t u r e - C o m m e r c i a l i s a t i o n

a n n o u n c e d

P resen t - In p r o d u c t i o n

( U . S . A . )

F u t u r e - N o t k n o w n

P r e sen t - In d e v e l o p m e n t F u t u r e - N o t k n o w n

M i c r o b i a l a l g i n a t e P r esen t - In d e v e l o p m e n t

F u t u r e - P r o m i s i n g

Bake rs Y e a s t G I y e a n

C u r d l a n

P r esen t - In d e v e l o p m e n t F u t u r e - N o t k n o w n

P resen t - In d e v e l o p m e n t

F u t u r e - N o t k n o w n

V a r i o u s

K e l t r o l K e l z a n R h o d i g e l 2 3

P u l l u l a n

Z a n f l o

B Y G

D e x t r a n P r o d u c t s Pol y d e x

K e l c o C o .

R h o n e P o u l e n c / G e n e r a l M i l l s T a t e & L y l e / H e r c u l e s

H a y a s h i b a r a C o r p .

K e l c o C o .

P o l y t r a n F . S . P i l l s b u r y

T a t e & L y l e L t d . / H e r c u l e s

A n h e u s e r - Busch I n c .

T a k e d a C h e m i c a l I n d .

Dow

nloa

ded

by U

NIV

OF

MIS

SOU

RI

CO

LU

MB

IA o

n A

pril

22, 2

013

| http

://pu

bs.a

cs.o

rg

Pub

licat

ion

Dat

e: J

une

1, 1

977

| doi

: 10.

1021

/bk-

1977

-004

1.ch

021



T a b l e I V. T h e C o n s u m p t i o n o f I ndus t r i a l G u m s in T h e U n i t e d S t a t e s ( 1 9 7 3 ) * (Tonnes )

G u m F o o d U s e s I ndus t r i a l T o t a l

C o r n s u g a r s 2 , 2 3 2 , 1 4 2 ? -C o r n s t a r c h 2 2 3 , 2 1 4 1 , 1 1 6 , 0 7 1 1 , 3 3 9 , 2 8 5

C a r b o x y m e t h y l e e l 1 u l o s e 6 , 6 9 6 4 3 , 3 0 3 5 0 , 0 0 0

M e t h y l e e l l u i ose 9 0 0 2 3 , 6 6 0 2 4 , 5 5 3

G u a r 6 , 6 9 6 1 5 , 6 2 5 2 2 , 3 2 1

A r a b i c 1 0 , 2 6 7 3 , 1 2 5 1 3 , 3 9 2

P e c t i n 5 , 3 5 7 0 5 , 3 5 7

L o c u s t b e a n 4 , 0 1 7 1 , 7 8 5 5 , 8 0 3

A l g i n a t e 4 , 0 1 7 4 , 0 1 7 8 , 0 3 4

G h a t t i 4 , 4 6 4 4 4 6 4 , 9 1 0

C a r r a g e e n a n 4 , 0 1 7 8 9 4 , 1 0 6

X a n t h a n 1 , 0 0 0 2 , 6 7 8 3 , 6 7 8

K a r a y a 4 4 6 3 , 1 2 5 3 , 5 7 1

T r a g a c a n t h 5 8 0 8 9 6 6 9

A g a r 133 178 311

F u r c e l l a r a n 8 9 0 8 9

* R . L . W h i s t l e r 1 9 7 4 ( u n p u b l i s h e d resul ts )

Dow

nloa

ded

by U

NIV

OF

MIS

SOU

RI

CO

LU

MB

IA o

n A

pril

22, 2

013

| http

://pu

bs.a

cs.o

rg

Pub

licat

ion

Dat

e: J

une

1, 1

977

| doi

: 10.

1021

/bk-

1977

-004

1.ch

021


to

00

oo

Tabl

e V.

M

icro

bia

l P

oly

sacc

ha

rid

es

of

Co

mm

erc

ial

Imp

ort

an

ce

(Pro

cess

In

form

ati

on

)

Na

me

De

xtr

an

Xa

nth

an

gu

m

Pu

llu

lan

Erw

inia

Ex

op

oly

sa

cc

ha

rid

e

Sc

lero

glu

ca

n

Mic

rob

ial

alg

ina

te

Ba

ke

rs

Ye

as

t

GI

ye

an

Cu

rdla

n

Org

an

ism

Le

uc

on

os

toc

me

sen

tero

ide

s

Xa

nth

om

on

as

cam

pe

stri

s

Au

reo

ba

sid

ium

pu

llu

lon

s

Erw

inia

tah

itic

a

Scl

ero

tiu

m

glu

ca

nic

um

Az

oto

ba

cte

r

vin

ela

nd

ii

Sa

cc

ha

rom

yc

es

cere

visi

ae

Ty

pe

of

Pro

cess

S

ub

stra

te

cell

fr

ee

en

zy

me

glu

cose

(su

cro

se)

ba

cte

ria

l

fun

ga

l

ba

cte

ria

l

fun

ga

l

ba

cte

ria

l

ye

as

t

glu

cose

glu

cose

sy

rup

Co

mp

on

en

t su

gar

o

f p

oly

me

r

glu

cose

glu

cose

(a

ceta

te)

glu

cu

ron

ic

ac

id

ma

nn

ose

(p

yru

vate

)

glu

co

se

syru

p g

luco

se

glu

co

se

?

glu

co

se

syru

p?

glu

co

se

sucr

ose

Ag

rob

ac

teri

um

sp

b

act

eri

al

Alc

ali

ge

ne

s fa

eca

l is

glu

cose

glu

cose

glu

cose

ga

lact

ose

fuco

se

uro

nic

a

cid

(a

ce

tyl)

glu

cose

ma

nn

uro

nic

a

cid

gu

luro

nic

a

cid

(ac

eta

te)

glu

cose

ma

nn

ose

glu

cose

o o

Dow

nloa

ded

by U

NIV

OF

MIS

SOU

RI

CO

LU

MB

IA o

n A

pril

22, 2

013

| http

://pu

bs.a

cs.o

rg

Pub

licat

ion

Dat

e: J

une

1, 1

977

| doi

: 10.

1021

/bk-

1977

-004

1.ch

021



Table VI, Some Important Physical Properties of Industrial Gums and their Applications

Physical Property

Cold set, clear, gel formation with divalent cations

Gel formation with sucrose

Heat reversible gel formation

Heat reversible gel formation in the presence of potassium ions

Non-reactivity with 'reactive' (Procion) dyestuffs

Stability in the presence of strong acids

Pseudoplastic behaviour under conditions of high shear

Synergistic gel formation with carob and guar gums

Retardation of sugar crystallisation Gum Arabic at low moisture contents

Gum

Alginate

Pectin

Agar

Carrageenan

Alginate

Xanthan gum

Xanthan gum

Xanthan gum

Application

Re-formed fruit pieces Dental gels

Jam manufacture

Microbiological solid media Synthetic meat gels

Synthetic meat gels Instant desserts

Textile print paste thickener

In rust curing gels containing phosphoric acid

As a lubricant for the ben ton i te muds used to drill oil wells

Synthetic meat gels

In pastilles and jujubes

i s p o s s i b l e t o use p r e c i s e l y d e f i n e d m edia c o m p o s i t i o n s . I n t h e a c t u a l p r o c e s s o f f e r m e n t a t i o n , o n g o i n g p a r a m e t e r s s u c h as pH, t e m p e r a t u r e , f e r m e n t a t i o n t i m e , d i l u t i o n r a t e and a e r a t i o n c a n be c o n t r o l l e d and m a n i p u l a t e d . Two i n t e r r e l a t e d r e s u l t s p o t e n t i a l l y a r e p o s s i b l e t h r o u g h t h e s e c o n t r o l s . The f i r s t i s t h e m a i n t e n a n c e o f p r o d u c t s p e c i f i c a t i o n s w i t h i n d e f i n e d l i m i t s , and t h i s i s p a r t i c u l a r l y v i t a l i n p o l y s a c c h a r i d e f e r m e n t a t i o n s where even s m a l l changes i n c e r t a i n p r o c e s s v a r i a b l e s c a n have d r a m a t i c e f f e c t s on po l y m e r s t r u c t u r e and, t h e r e f o r e , p h y s i c a l b e h a v i o u r . T h i s , i n c i d e n t a l l y , i s one r e a s o n why t h e use o f c o n t i n u o u s c u l t u r e i s f a v o u r e d . Under s t e a d y s t a t e c o n d i t i o n s , t h e v a r i a b l e s o f f e r m e n t a t i o n a r e h e l d c o n s t a n t w i t h r e s p e c t t o e a c h o t h e r , t h u s a f f o r d i n g a much b e t t e r u n d e r s t a n d i n g and c o n t r o l o f t h e p r o c e s s .

The s e c o n d e f f e c t i s t h e p o t e n t i a l a b i l i t y t o mani p u l a t e p r o d u c t t y p e and y i e l d . F o r example, t h e a b i l i t y t h r o u g h s p e c i f i c changes i n f e r m e n t a t i o n c o n d i t i o n s t o p r o d u c e r a n g e s o f m i c r o b i a l gums o f a p a r t i c u l a r t y p e , d i f f e r i n g i n m o l e c u l a r w e i g h t . A n o t h e r a d v a n t a g e o f f e r m e n t a t i o n i s t h a t , i n p r o d u c t r e c o v e r y , h a r s h e x t r a c t i o n t e c h n i q u e s n o r m a l l y a r e n o t r e q u i r e d and, v e r y o f t e n , s o l v e n t p r e c i p i t a t i o n may be contemp l a t e d w h i c h , o f c o u r s e , i s a v e r y m i l d t r e a t m e n t , n o t l i k e l y t o l e a d t o p r o d u c t d e g r a d a t i o n . The c h o i c e

Dow

nloa

ded

by U

NIV

OF

MIS

SOU

RI

CO

LU

MB

IA o

n A

pril

22, 2

013

| http

://pu

bs.a

cs.o

rg

Pub

licat

ion

Dat

e: J

une

1, 1

977

| doi

: 10.

1021

/bk-

1977

-004

1.ch

021


290 SUCROCHEMISTRY

T a b l e V I I . B e n e f i t s O b t a i n e d i n P r o d u c i n g P o l y s a c c h a r i d e s

by F e r m e n t a t i o n

1 . M e d i u m P r e p a r a t i o n

(a) R a w m a t e r i a l s i n p l e n t i f u l s u p p l y

(b) P r e c i s e l y d e f i n e d m e d i a p o s s i b l e

2 . F e r m e n t a t i o n

(a) H i g h d e g r e e o f p r o c e s s c o n t r o l p o s s i b l e

(b) C o n t i n u o u s c u l t u r e p o s s i b l e / , h i g h p r o d u c t i v i t y

3. P r o d u c t R e c o v e r y

(a) M i l d c o n d i t i o n s c a n be u s e d . M i t t l e p r o d u c t

d e g r a d a t i o n .

T a b l e V I I I .

T e c h n i c a l P r o b l e m s i n M i c r o b i a l P o l y s a c c h a r i d e P r o d u c t i o n

H i g h b r o t h v i s c o s i t i e s , r e s u l t i n g in :

( i ) L o w p r o d u c t c o n c e n t r a t i o n , t h e r e f o r e

l a r g e v o l u m e s of w a t e r

l a r g e f e r m e n t e r c a p a c i t y

( i i ) H i g h e n e r g y r e q u i r e m e n t s f o r

o x y g e n t r ans f e r

b u l k m i x i n g

w a t e r r e m o v a l

( i i i ) D i f f i c u l t i e s i n c e l l r e m o v a l .

Dow

nloa

ded

by U

NIV

OF

MIS

SOU

RI

CO

LU

MB

IA o

n A

pril

22, 2

013

| http

://pu

bs.a

cs.o

rg

Pub

licat

ion

Dat

e: J

une

1, 1

977

| doi

: 10.

1021

/bk-

1977

-004

1.ch

021


21. L A W S O N Industrially Important Gums 291

o f p r o d u c t i o n s i t e s c a n be f a i r l y f l e x i b l e , l i m i t e d m a i n l y by t h e a v a i l a b i l i t y o f w a t e r . F i n a l l y , t h e use of c o n t i n u o u s c u l t u r e c a n enhance p r o d u c t i v i t i e s o v e r t h o s e o b t a i n e d i n b a t c h c u l t u r e s , as c e l l s a r e grown a l w a y s under c o n d i t i o n s most c o n d u c i v e t o e f f i c i e n t p r o d u c t f o r m a t i o n .

T u r n i n g t o t h e d i s a d v a n t a g e s o f f e r m e n t a t i o n ( T a b l e V I I I ) , t h e y c a n be summarised as b e i n g c a u s e d l a r g e l y by t h e h i g h l y v i s c o u s f e r m e n t a t i o n b r o t h s e n c o u n t e r e d . T h i s s e v e r e l y l i m i t s t h e c o n c e n t r a t i o n s o f p o l y m e r i t i s p r a c t i c a b l e t o s y n t h e s i z e . The ran g e 30-40,000 c p s i s n o t uncommon and no c o n c e n t r a t i o n s o f gum above a b o u t 4% ca n be c o n t e m p l a t e d . I t f o l l o w s , t h e r e f o r e , t h a t v e r y l a r g e f e r m e n t e r s a r e r e q u i r e d i n o r d e r t o s y n t h e s i s e e c o n o m i c a l l y s e n s i b l e t o n n a g e s o f gum. F e r m e n t e r s i z e s o f 50-200 m^ a r e p r a c t i c a l . V e r y l a r g e volumes o f b o t h w a t e r and p r o d u c t r e c o v e r y s o l v e n t a r e r e q u i r e d , so t h a t e f f l u e n t p r o b l e m s must be c o n t e m p l a t e d , u n l e s s r e c y c l i n g i s t o be u n d e r t a k e n . O t h e r p r o b l e m s l i e i n t h e h i g h power r e q u i r e m e n t s needed t o o b t a i n s a t i s f a c t o r y b r o t h m i x i n g and a e r a t i o n w h i c h , i f n o t a d e q u a t e , c a n l e a d q u i c k l y t o oxygen l i m i t a t i o n and l o w e r e d p o l y s a c c h a r i d e p r o d u c t i v i t i e s . F i n a l l y , c e l l r e m o v a l , p a r t i c u l a r l y by m e c h a n i c a l means ( c e n t r i f u g e , f i l t e r s ) , i s d i f f i c u l t and, a l t h o u g h methods b a s e d on enzyme d i g e s t i o n o f c e l l s (1) and a l k a l i d i g e s t i o n have been p u b l i s h e d (2^) ,many p r o b l e m s have y e t t o be s o l v e d .

I n summary, i t i s i m p o r t a n t t o p o i n t o u t t h a t , a l t h o u g h f e r m e n t a t i o n as an a p p r o a c h t o p o l y s a c c h a r i d e p r o d u c t i o n i s n o t w i t h o u t p r o b l e m s , t h e c o n c e p t c o u l d , i n t h e f u t u r e , r e v o l u t i o n i z e many a s p e c t s o f i n d u s t r i a l gum p r o d u c t i o n .

A s p e c t s o f t h e work b e i n g u n d e r t a k e n i n t o t h e p r o d u c t i o n o f m i c r o b i a l a l g i n a t e a t t h e T a t e and L y l e Labo r a t o r i e s now w i l l be examined. B r i e f l y , a l g i n a t e i s b e s t known as t h e p o l y s a c c h a r i d e o b t a i n e d f r o m brown a l g a e s u c h as s p e c i e s o f L a m i n a r i a and M a c r o c y s t i s ( F i g u r e 1 ) . I t i s a l i n e a r p o l y m e r o f ß-D-mannuronic a c i d and a - L - g u l u r o n i c a c i d . The arr a n g e m e n t o f t h e monomers has been s t u d i e d by Haug and c o - w o r k e r s (3) and Rees and c o - w o r k e r s (4_) and r e f e r r e d t o as t h e b l o c k s t r u c t u r e . T h a t i s , h o m o p o l y m e r i c b l o c k s o f man n u r o n i c and g u l u r o n i c a c i d c o m p r i s e t h e so c a l l e d , " a l t e r n a t i n g r e g i o n s " . The f l o w and g e l - f o r m i n g p r o p e r t i e s o f t h e p o l y m e r i n aqueous s o l u t i o n depend on t h e p r o p o r t i o n s o f t h e m o n o s a c c h a r i d e r e s i d u e s , on t h e i r a r r a n g e m e n t and on t h e p o l y m e r m o l e c u l a r w e i g h t . T h i s a p p l i e s v e r y much t o g e l f o r m a t i o n i n t h e p r e s e n c e o f d i v a l e n t m e t a l c a t i o n s a s , f o r example, a l g i n a t e s

Dow

nloa

ded

by U

NIV

OF

MIS

SOU

RI

CO

LU

MB

IA o

n A

pril

22, 2

013

| http

://pu

bs.a

cs.o

rg

Pub

licat

ion

Dat

e: J

une

1, 1

977

| doi

: 10.

1021

/bk-

1977

-004

1.ch

021


292 SUCROCHEMISTRY

M o n o m e r s

^ - D - M a n n u r o n i c a c i d oC - L - G u l u r o n i c a c i d

B l o c k S t r u c t u r e

- M - M - M - M - M - M -

- G - G - G - G - G - G -

- M - G - M - G - M - G -

Figure 1. Structure of alginic acid

h a v i n g a h i g h p r o p o r t i o n o f g u l u r o n i c a c i d p a r t i c u l a r l y as homopolymers f f o r m t h e s t r o n g e s t and most b r i t t l e g e l s . The e x o c e l l u l a r p o l y s a c c h a r i d e p r o d u c e d by A z o t o b a c t e r v i n e l a n d i i has been shown i n i t i a l l y by G o r i n and S p e n c e r (5») and by t h e l a t e Arne Haug and c o - w o r k e r s (6) t o have t h e same b a s i c s t r u c t u r e as t h a t f r o m a l g a l s o u r c e s e x c e p t t h a t a m a l l number o f h y d r o x y 1 g r o u p s were a c e t y l a t e d .

I n t h e T a t e and L y l e s t u d y o f A z o t o b a c t e r a l g i n a t e t h e o b j e c t i v e has been t h e de v e l o p m e n t o f a p r o d u c t w h i c h w o u l d compete b o t h i n b e h a v i o u r and economic terms w i t h t h e a l g a l m a t e r i a l s on s a l e i n w o r l d m a r k e t s . E a r l y s t u d i e s i n b a t c h c u l t u r e u n d e r t h e c o n d i t i o n s d e s c r i b e d by G o r i n and Sp e n c e r (5), gave p o o r p r o d u c t s , o b t a i n e d i n v e r y l o w y i e l d . S ubsequent improvements were made by g r o w i n g t h e o r g a n i s m u n d e r p h o s p h a t e def i c i e n t c o n d i t i o n s (!) p l u s o t h e r m o d i f i c a t i o n s w h i c h i n c r e a s e d t h e c o n s i s t e n c y i n d e x (a measure o f f l o w b e h a v i o u r i n aqueous s o l u t i o n ) f r o m ^30 c p s t o 4,000 c p s , t h u s c o v e r i n g t h e rang e o f c o m m e r c i a l l y a v a i l a b l e , a l g a l a l g i n a t e s . T h i s w i d e r a n g e o f p r o d u c t v i s c o s i t i e s a l s o has been o b t a i n e d f r o m c o n t i n u o u s c u l t u r e s ( F i g u r e 2 ) . The most v i s c o u s p r o d u c t has a c o n s i s t e n c y i n d e x o f 6,000 cps ( 1 % c o n c e n t r a t i o n ) . The g e l -f o r m i n g p r o p e r t i e s o f m i c r o b i a l a l g i n a t e a l s o were d e m o n s t r a t e d t o be s i m i l a r t o t h e i r a l g a l c o u n t e r p a r t s .

Dow

nloa

ded

by U

NIV

OF

MIS

SOU

RI

CO

LU

MB

IA o

n A

pril

22, 2

013

| http

://pu

bs.a

cs.o

rg

Pub

licat

ion

Dat

e: J

une

1, 1

977

| doi

: 10.

1021

/bk-

1977

-004

1.ch

021



I n b a t c h c u l t u r e s , t h e h i g h e s t y i e l d s o f sodium a l g i n a t e p o s s i b l e t o o b t a i n u n d e r p h o s p h a t e d e f i c i e n t c o n d i t i o n s , were f o u n d t o a p p r o x i m a t e 25% o f t h e s u c r o s e u t i l i s e d ( F i g u r e 3 ) • H i g h r e s p i r a t i o n i n A . v i n e -l a n d i i i s a w e l l - k n o w n phenomenon and,as a r e s u l t un-d e r c e r t a i n c o n d i t i o n s , much o f t h e s u c r o s e c a n be u t i l i z e d i n an u n c o n t r o l l e d manner and l o s t as c a r b o n d i o x i d e . I t , t h e r e f o r e , w a s d e c i d e d t o i n v e s t i g a t e t h e e f f e c t o f r e s p i r a t i o n on a l g i n a t e p r o d u c t i o n i n c o n t i n uous c u l t u r e ; a t e c h n i q u e h a v i n g t h e p o t e n t i a l o f much

1 0 , 0 0 0 p

1 10 10Ö TTürfo

Rate of shear (sec )̂

Figure 2. Apparent viscosity vs. rate of shear plots for Azotobacter alginates and certain commercial algal alginates

Dow

nloa

ded

by U

NIV

OF

MIS

SOU

RI

CO

LU

MB

IA o

n A

pril

22, 2

013

| http

://pu

bs.a

cs.o

rg

Pub

licat

ion

Dat

e: J

une

1, 1

977

| doi

: 10.

1021

/bk-

1977

-004

1.ch

021


294 SUCROCHEMISTRY

Cells

o Alginate

• -^iginate/Cells

Figure 3. Effect of phosphate concentration on alginic acid synthesis by Azotobacter vinelandii in batch culture

g r e a t e r c o n t r o l . P h o s p h a t e - l i m i t e d g r o w t h c o n d i t i o n s were c h o s e n , as a p a u c i t y o f p h o s p h a t e was i n d i c a t e d by th e work i n b a t c h c u l t u r e . R e s p i r a t i o n r a t e was c o n t r o l l e d by m a n i p u l a t i n g f e r m e n t e r i m p e l l e r s p e e d s , r e s u l t i n g i n a l t e r e d oxygen t r a n s f e r i n t o t h e fermen t a t i o n b r o t h . T h e r e f o r e , a l t h o u g h c e l l mass was c o n t r o l l e d a t an e s s e n t i a l l y c o n s t a n t l e v e l by t h e pho s p h a t e a v a i l a b i l i t y , t h e s p e c i f i c r e s p i r a t i o n r a t e was d e t e r m i n e d by t h e a v a i l a b i l i t y o f oxygen ( F i g u r e 4). Under t h e above c o n d i t i o n s , a t l o w e r r e s p i r a t i o n r a t e s , t h e maximum y i e l d o f sodium a l g i n a t e was i n t h e r e g i o n o f 45% o f t h e s u c r o s e u t i l i s e d . A t h i g h e r r e s p i r a t i o n r a t e s , t h e y i e l d f e l l d r a m a t i c a l l y due t o a g r e a t e r p r o p o r t i o n o f s u c r o s e b e i n g b u r n e d o f f as C O 2 .

I n c o n c l u s i o n , t h e p r o d u c t i o n o f m i c r o b i a l p o l y s a c c h a r i d e s o f c o m m e r c i a l s i g n i f i c a n c e i s now a w e l l e s t a b l i s h e d f a c t and a new g e n e r a t i o n o f w a t e r s o l u b l e p o l y m e r s i s b e i n g i d e n t i f i e d . However, t h e p r o d u c t i o n t e c h n o l o g i e s a r e e x p e n s i v e , r e l a t i v e t o many o f t h e p l a n t gums. B i o p o l y m e r s w i l l o n l y g a i n a f u l l y e s t a b l i s h e d c o m p e t i t i v e p o s i t i o n l e a d i n g t o t h e use o f i n d u s t r i a l s c a l e c o n t i n u o u s c u l t u r e s t h r o u g h t h e s u c c e s s o f c u r r e n t r e s e a r c h programmes i n t o t h e p h y s i o l o g y o f e x o p o l y s a c c h a r i d e s y n t h e s i s .

Abstract In recent years, the exocellular polysaccharide

elaborated by the bacterium Xanthomonas compestris has emerged as a product with significant industrial appli—

Dow

nloa

ded

by U

NIV

OF

MIS

SOU

RI

CO

LU

MB

IA o

n A

pril

22, 2

013

| http

://pu

bs.a

cs.o

rg

Pub

licat

ion

Dat

e: J

une

1, 1

977

| doi

: 10.

1021

/bk-

1977

-004

1.ch

021



cation, and the present annual world consumption is several thousand tons. This has demonstrated the potential of fermentation for producing polysaccharides having unusual solution and gel properties. At the present time there is an increasing demand for xanthan gum and new applications appear regularly in the patent literature and elsewhere. It is likely that other microorganisms wi l l be capable of producing commercially valuable polysaccharides and, as a consequence, a number of systems are under investigation with several apparently at an advanced stage of development. Tate and Lyle became interested in microbial gums through reports that the bacteria Azotobacter vinelandii and Pseudomonas aeruginosa produce polysaccharides similar to the polyuronide, alginic acid. The sole source of this polysaccharide at present is the brown algae from which approximately 20,000 tons of alginate are extracted per annum. Pseudomonas aeruginosa was rejected for study due to its association with pathogenic conditions in man. As initial assessments indicated that the Azotobacter polysaccharide could be commercially valuable if sufficiently high yields were

1.5,-

Figure

0 10 20 30 40

Specific respiration rate (pmol O^/h/mg cell)

Exopolysaccharide production by Azotobacter vinelandii at a range of respiration rates

Dow

nloa

ded

by U

NIV

OF

MIS

SOU

RI

CO

LU

MB

IA o

n A

pril

22, 2

013

| http

://pu

bs.a

cs.o

rg

Pub

licat

ion

Dat

e: J

une

1, 1

977

| doi

: 10.

1021

/bk-

1977

-004

1.ch

021


296 SUCROCHEMISTRY obtained, the latter was selected for further study. Subsequent developments to pilot plant level have involved improving yield and controlling and manipulating the physical properties of the polymer produced by appropriate choice of growth media and fermentation conditions, using both batch and continuous culture and also by strain selection. Literature Cited 1. Kelco Co., British Patent, 1,443,507, (1975). 2. Patton, J.T., United StaTes Patent, 3,729,460,

(1970). 3. Larsen, B. , Smidsrod, O., Haug, A. and Painter, T. Acta. Chem. Scand., (1969), 23, 2375. 4. Rees, D.A., Biochem. J., (1972), 126, 257. 5. Gorin, P.A.J, and Spencer, J.F.T., Canad. J. Chem.

(1966), 44, 993. 6. Larsen, B. and Haug, A. , Carbohyd. Res., (1971),

17, 287. 7. Imrie, F.K.E., British Patent, 1,331,771, (1973). Biographic Notes

Christopher J . Lawson, Ph.D., Project Leader -Microbiological Polysaccharides. Educated at the Univ. of Edinburgh. Joined Tate and Lyle, Ltd., in 1969, specializing in microbiological polysaccharides by fermentation. Tate and Lyle, Ltd., Philip Lyle Memorial Research Laboratory, P.O. Box 68, Reading, Berkshire RG6 2BX, England.

Dow

nloa

ded

by U

NIV

OF

MIS

SOU

RI

CO

LU

MB

IA o

n A

pril

22, 2

013

| http

://pu

bs.a

cs.o

rg

Pub

licat

ion

Dat

e: J

une

1, 1

977

| doi

: 10.

1021

/bk-

1977

-004

1.ch

021


[acs symposium series] sucrochemistry volume 41 || production of industrially important gums with...

Documents