fermentation of lignocellulose hydrolysates with yeasts and xylosisomerase

Upload: alicemedeiros

Post on 02-Jun-2018

221 views

Category:

Documents


0 download

TRANSCRIPT

  • 8/10/2019 Fermentation of Lignocellulose Hydrolysates With Yeasts and XylosIsomerase

    1/7

  • 8/10/2019 Fermentation of Lignocellulose Hydrolysates With Yeasts and XylosIsomerase

    2/7

    apers

    r a b le t o t h o s e o b t a i n e d i n h e x o s e f e r m e n t a t i o n . W e a r e

    w e l l a w a r e t h a t i t i s q u i t e i m p o s s i b l e t o u s e a z i d e i n a n

    i n d u s t r i a l p r o c e s s , b u t a t t h is l e v e l it o f f e r s a m e a n s o f

    s t u d y i n g th e m e c h a n i s m s o f d e p r e s s i n g b y - p r o d u c t

    f o r m a t i o n .

    I n t h e p r e s e n t s t u d y w e h a v e c o m p a r e d t h e f e r m e n -

    t a t i o n o f u n t r e a t e d s p e n t s u l p f it e l iq u o r ( S S L ) a n d

    u n t r e a t e d h y d r o g e n f l u o r i d e - p r e t r e a t e d a n d a c i d -

    h y d r o l y s e d w h e a t s t r a w ( H F s t ra w ) w i t h f iv e d i f fe r e n t

    n o n a d a p t e d y e a s t s a n d f o u r d if f e r e n t c o m m e r c i a l

    x y l o s e i s o m e r a s e s . T h e a i m w a s t o c o m p a r e t h e p e r -

    f o r m a n c e o f t h e y e a s t s a n d t h e e n z y m e s i n a n u n -

    t r e a t e d l i g n o c e l l u l o s e h y d r o l y s a t e .

    a t e r ia l s a n d m e t h o d s

    R a w m a t e r i a l s

    S p e n t s u if i te l i q u o r ( S S L ) , s o d i u m b a s e d , w a s s u p p l i e d

    b y M O D O , O r n s k O l d s v i k , S w e d e n . H y d r o g e n fl uo -

    r i d e - p r e t r e a t e d a n d a c i d - h y d r o l y s e d s tr a w ( H F s t r a w )

    w a s s u p p l i e d b y t h e I n s t i t u te o f B i o t e c h n o l o g y ,

    K o l d i n g , D e n m a r k . T h e o n l y p r e t r e a t m e n t o f t h e

    s u b s t r a t e s w a s t h e a d j u s t m e n t o f p H t o 6 .0 w i th K O H

    a n d a d d i t io n o f f e r m e n t a t i o n n u t r i e n ts : 0 . 2 5 % ( w / v )

    y e a s t e x t r a c t ( D i f c o , D e t r o i t , U S A ) a n d 0 . 0 2 5 % ( w / v )

    ( N H 4 ) 2 H P O 4 ; M g S O 4 7 H 2 0 w a s a d d e d i n f e r m e n t a -

    t i o n s w i t h o u t x y l o s e i s o m e r a s e ( X I ) to a c o n c e n t r a t i o n

    o f 0 . 0 0 2 5 % ( w / v ) , o t h e r w i s e t o 0 . 2 % ( w / v ) . T h e s u b -

    s t r a t e s w e r e b u f f e r e d w i t h s o l i d 0. 1 M s o d i u m p h o s -

    p h a t e a n d , i f n e c e s s a r y , t h e p H w a s r e a d j u s t e d t o 6 . 0.

    M i c r o o r g a n i s m s a n d g r o w t h m e d i u m

    Candida t ropica l i s

    ( A T C C 3 2 1 1 3 ) ,

    Pichia s t ip i t i s

    ( C B S 5 7 7 6 ) , a n d P a c h y so l e n t a n n o p h i lu s ( C B S 4 0 4 4 )

    w e r e m a i n t a i n e d o n Y M P a g a r w i t h x y l o s e , 1 0 g I ].

    S c h i z o s a c c h a r o m y c e s p o m b e

    ( C B S 3 5 2 ) w a s m a i n -

    t a i n e d o n Y M P a g a r w i t h g l u c o s e , l 0 g 1 t. S a c c h a ro -

    myces cerev is iae , c o m p r e s s e d b a k e r s ' y e a s t , w a s

    o b t a i n e d f r o m a l o c a l d i s t r i b u t o r .

    C e l l m a s s w a s p r o d u c e d i n 2-1 b a f f l e d E r l e n m e y e r

    f l a s k s, f i ll ed t o 2 5 0 m l a n d s e a l e d w i t h c o t t o n s t o p p e r s ,

    o n a r o t a r y s h a k i n g w a t e r b a t h a t 3 0 C .

    G r o w t h m e d i u m f o r c el l m a s s p r o d u c t i o n w a s t h e

    f o l l o w i n g : y e a s t e x t r a c t , 3 g l t ( D i f c o , D e t r o i t , U S A ) ,

    m a l t e x t r a c t b r o t h , 3 g 1 ~ ( D i f c o , D e t r o i t , U S A ) ;

    b a c t o - p e p t o n e , 5 g I ~ ( D i f c o , D e t r o i t , U S A ) ; K H 2 P 0 4 ,

    19 g l - I , ( NH 4) 2H P O4 , 3 g 1 j , M gS O 4 7 H2 0, 1 .1 g 1 l ,

    x y l o s e , 3 0 g I ~ ( S i g m a C h e m i c a l C o m p a n y , S t . L o u i s ,

    U S A ) ( f o r C. tropicalis , P. st ipit is , a n d P. tanno-

    phi lus ;

    g l u c o s e , 3 0 g I ~ ( f o r

    S . p o m b e .

    X y l o s e a n d

    g l u c o s e w e r e a u t o c l a v e d s e p a r a t e l y . T h e y e a s t s w e r e

    h a r v e s t e d i n l a t e l o g p h a s e b y c e n t r i f u g a t i o n ( a t

    1 4 , 0 0 0 ~ , , , 1 5 m i n , 4 C B e c k m a n m o d e l J 2 - 2 1 ) . T h e d r y

    w e i g h t w a s d e t e r m i n e d a n d t h e c e l ls w e r e u s e d f o r t h e

    f e r m e n t a t i o n o f th e l i g n o c e l lu l o s e h y d r o l y s a t e s .

    E n z y m e s

    W e u s e d f o u r d i f f e re n t c o m m e r c i a l e n z y m e p r e p a r a -

    t io n s w h i c h w e r e g e n e r o u s l y s u p p l i e d b y t h e p r o -

    d u c e r s , X I ( A ) - O p t i s w e e t - P k o n z ( t h r o u g h M i l e s

    K a l i - C h e m i e , H a n n o v e r , F R G ) , X I ( B ) - N O V O

    S w e e t z y m e Q ( N o v o I n d u s tr i A / S , B a g s v a e r d , D e n -

    m a r k ) , X I ( C ) - G I S T B r o c a d e s M a x a z y m e G I -

    I m m o b ( G I S T B r o c a d e s , D e l f t, T h e N e t h e r l a n d s ) , a n d

    X I ( D ) = T a k a s w e e t ( t h r o u g h M i l e s K a l i - C h e m i e ,

    H a n n o v e r , F R G ) . X I ( A ) i s a s o li d w h o l e - c e l l n o n i m -

    m o b i l i z e d e n z y m e p r e p a r a t i o n u s e d i n t h e f e rm e n t a -

    t i o n s . X I ( A ) i s a l s o a v a i l a b l e i n a l i q u i d f o r m w i t h o u t

    c e ll s. T h i s w a s u s e d o n c e f o r d e t e rm i n i n g e n z y m e

    a c t i v i t y i n s o d i u m c h l o r i d e s o l u t i o n . T h e o t h e r t h r e e

    e n z y m e s a r e i m m o b i l i z e d .

    F e r m e n t a t i o n c o n d i t i o n s

    A 1 5 0 - m l , s l o w l y s t i r r e d , t h e r m o s t a t e d ( 3 0 C ) , f i ll e d

    b e a k e r , s e a l e d w i t h a r u b b e r s t o p p e r , w a s i n o c u l a t e d

    w i t h y e a s t , 7 5 g I t d r y w e i g h t . F o r P . t a n n o p h i lu s a n d

    S. pornbe , 5 3 a n d 5 2 . 5 g I - I , r e s p e c t i v e l y , w e r e u s e d .

    F o r t h e c o - c u l t u r e o f

    P . t a n n o p h i lu s

    a n d

    S. cerev is iae

    w e u s e d 3 7 .5 g I t o f e a c h y e a s t . W h e n u s e d , X I w a s

    a d d e d i n t h e f o l lo w i n g c o n c e n t r a t i o n s i n o r d e r t o u s e

    c o m p a r a b l e e n z y m e ( g l u c o s e i s o m e r a s e ) a c t i v i ty i n all

    e x p e r i m e n t s : X I (A ) 1 0 g I ~; i n r e p e a t e d b a t c h f e r m e n -

    t a t i o ns XI ( B) 145 g I - ~, XI ( C ) 70 g I - ~, and XI ( D ) 57 .5

    g 1 ~ . O t h e r w i s e X I ( C ) w a s u s e d a t a c o n c e n t r a t i o n o f

    5 0 g I J. W h e n u s e d , a z i d e w a s a d d e d t o a f i n al

    c o n c e n t r a t i o n o f 4 . 6 raM . T h e d a t a p r e s e n t e d a r e t h e

    a v e r a g e o f at l e as t t w o e x p e r i m e n t s .

    A n a l y s i s

    E t h a n o l , s u g a r s , a n d b y - p r o d u c t s w e r e m e a s u r e d w i t h

    a V a r i a n 5 0 0 0 l i q u i d c h r o m a t o g r a p h w i t h a T e c a t o r

    O p t i l a b 5 9 02 r e f r a c t o m e t e r . F o r e t h a n o l , a c e t i c a c i d ,

    g l y c e r o l , x y l it o l , g l u c o s e , a r a b i n o s e , a n d t o t a l c o n t e n t

    o f x y l o s e , m a n n o s e , a n d g a l a c t o s e , a B i o -R a d a m i n e x

    H P X - 8 7 H c o l u m n a t 4 5 C w a s u s e d w i t h a f l o w r a t e o f

    0 . 6 m l r a i n - t a n d 0 . 0 0 5 M H 2 S O 4 a s m o b i l e p h a s e .

    C o m p l e t e s u g a r a n a l y s is w a s p e r f o r m e d w i t h a B io -

    R a d a m i n e x H P X - 8 7 P c o l u m n a t 8 5 C , fl o w r a t e 0 .6 m l

    r a in t , a n d w a t e r a s m o b i l e p h a s e . T h e s a m p l e s f o r t h e

    l e a d c o l u m n w e r e d e i o n i z e d w i t h a m i x e d - b e d i o n -

    e x c h a n g e r e s i n . G l u c o s e i s o m e r a s e a c t i v i ty w a s d e t e r -

    m i n e d a c c o r d i n g t o G o n g et al.14 T h e g l u c o s e f o r m e d

    w a s d e t e r m i n e d b y t h e g l u c o s e o x i d a s e m e t h o d . ~5 A l l

    c h e m i c a l s w e r e o f re a g e n t g r a d e . T h e e r r o r s i n t h e

    a n a l y s is o f t he f e r m e n t a t i o n s h a v e b e e n e s t i m a t e d t o

    b e l e s s t h a n 5 % .

    R e s u l t s a n d d i s c u s s io n

    R a w m a t e r ia l

    T h e s u g a r c o m p o s i t i o n o f S S L a n d H F s t ra w v a r i e s

    w i t h t h e s o u r c e o f r a w m a t e r i a l a n d s e a s o n .

    Figure 1

    s h o w s t h e s u g a r c o m p o s i t i o n o f tw o t y p i c a l s u b s tr a t e s .

    T h e s e a r e n o t t h e s u g a r c o n t e n t s o f th e o r i g in a l

    h y d r o l y s a t e s b u t f o r t h o s e i n o c u l a t e d w i t h 7 5 g I ~ d r y

    w e i g h t y e a s t , s i n c e a h ig h y e a s t c o n c e n t r a t i o n c a u s e d

    a d i l u t io n o f t h e h y d r o l y s a t e 1 .3 7 t i m e s . S S L a n d H F

    s t r a w h a v e q u i t e s i m i la r t o t a l s u g a r a n d x y l o s e c o n -

    t e n t s . T h e d i f f e r e n c e li e s w i t h i n t h e h e x o s e f r a c t i o n .

    584 Enzyme Microb. Technol. 1989 vol. 11 September

  • 8/10/2019 Fermentation of Lignocellulose Hydrolysates With Yeasts and XylosIsomerase

    3/7

    XYL GAL MANN ARA GLU TOT

    Sugar

    Figure 1 Sugar content of SSL filled) and HF straw shaded)

    An important difference between the substrates is

    their salinity. SSL has an estimated ionic strength of

    about 2

    M,

    mainly due to high amounts of sodium

    sulfite added in the pulping process. The salt concen-

    tration in HF straw is lower and arises from the acid

    hydrolysis and the neutralization.

    Fermentation of SSL with different yeasts

    First we compared ethanol production with the five

    yeasts C. tropicalis, P. stipitis, P. tannophilus, S.

    pomhe, and S.

    cereuisiae.

    In these fermentations we

    used azide and XI (A). Figure 2 shows the yield of

    ethanol per gram of total sugar. Thus, 0.5 is the

    theoretical maximum. Under our conditions the xy-

    lose-fermenting yeasts C. tropicalis, P. stipitis, and P.

    tannophilus give low yields of around 0.2. The hexose-

    and xylulose-fermenting yeasts S. cereuisiae and S.

    pombe give reasonable yields of about 0.4 and 0.3,

    respectively. In a co-culture of P. tannophilus and S.

    cereuisiae a yield of 0.3 was achieved.

    Sugar consumption, ethanol production, by-pro-

    duct formation, and yield are summarized in Table I.

    The velocity of the fermentations can be estimated

    from Figure 2. C. tropicalis consumed sugar quite well

    but produced by-products and did not produce ethanol

    in proportion to the sugar consumption. It has recently

    been suggested that this may be due to an excessive

    carbon dioxide production with this yeast in the pres-

    ence of azide.16 With P. stipitis the sugar consumption

    was very rapidly inhibited. Nevertheless, some etha-

    nol was produced, probably from stored carbohy-

    drates. P. tannophilus consumed sugar well but pro-

    duced large amounts of by-products. S. pombe

    consumed less sugar than the other yeasts, except for

    P. stipitis, but produced low amounts of by-products,

    and, thus, gave a better yield of ethanol. S. cereuisiae

    gave

    the best yield of ethanol. The co-culture of P.

    tannophilus and S.

    cerevisiae

    produced high amounts

    of by-products which lowered the yield of ethanol.

    The more than theoretical yield of ethanol based on

    Fermentation of lignocellulose hydrolysates: T. Linddn and B. Hahn Htigerdal

    consumed sugar with P.

    stipitis

    and S. cereuisiae

    (Table I)

    is probably due to the breakdown and

    fermentation of carbohydrate reserves, such as glyco-

    gen and trehalose, or the fermentation of an uniden-

    tified carbon source in SSL. The use of high cell mass

    in fermentations, especially in combination with azide,

    can influence the yield.

    .I* Therefore, we estimated

    the ethanol production from stored carbohydrates with

    S.

    cereuisiae

    (75 g 1-l dry weight) in buffer under the

    same conditions as for the fermentation of SSL, but

    with no carbon source added. With azide 1.5 g 1-l

    ethanol was produced, and 0 g 1-l without. Translating

    these numbers to the yield of ethanol in SSL fermenta-

    tion, we may introduce an error of 0.04, which is in

    agreement with the yield based on consumed sugars

    (Table I).

    This does not explain the extremely high

    yield obtained for

    P. stipitis.

    Because P. stipitis is so

    rapidly inhibited in SSL, we did not look further into

    this discrepancy.

    In order to confirm the influence of azide on the

    yield of ethanol, we also fermented SSL with S.

    cereuisiae, with and without azide (Figure 3). The

    difference in yield is slightly higher than 0.04. This

    seems to support our hypothesis that, under the condi-

    tions we have chosen for the fermentation of nonde-

    toxified lignocellulose hydrolysates (75 g 1-l dry

    weight cell mass and 4.6 mM azide), there is a contri-

    bution to the yield from stored carbohydrates.

    In the comparisons of the different yeasts, we did

    not use the same amount of cells in all experiments.

    Therefore we have also calculated the yield of ethanol

    based on initial cell mass (Table I). Also in this

    comparison S. pombe and S. cereuisiae give a signifi-

    cantly higher yield than the xylose-fermenting yeasts.

    Xylose isomeruses

    We then investigated the influence of various prepara-

    tions of xylose isomerase (XI) on the ethanol yield in

    o.51

    0 0

    10

    20

    30

    40

    50

    60

    Time h

    Figure 2 Time course of ethanol yield based on total sugars in

    SSL with five yeasts in the presence of Xl A) and 4.6 mM azide.

    x) C. Wopicalis; 0) P. stipitis; (H)P. tannophilus; (+)S. pombe;

    A) S. cerevisiae; A) S. cerevisiae + P. rannoph ilus

    Enzyme Microb. Technol., 1989, vol. 11, September 585

  • 8/10/2019 Fermentation of Lignocellulose Hydrolysates With Yeasts and XylosIsomerase

    4/7

    apers

    ( / )

    O

    c-

    A :

    33

    0.5

    0 . 4

    0.3

    0.2

    0.1

    0 , 0 I

    0 1 0 2 0 3 0 4 0 5 0 6 0

    T i m e h

    F igure 3 F e r m e n t a t i o n o f S S L w i t h S ce rev i s i ae w i t h I ) a n d

    w i t h o u t E l) a z i d e

    ]

    YIELD B)

    0.4 j [ ] YIELD C) I

    ~ 0.3

    ~ 0 2

    ~ 0 1

    0.0

    1 2 3 4

    B a t c h n o .

    F igure 4 E t h a n o l y i e l d b a s e d o n to t a l s u g a r i n r e p e a t e d b a t c h

    f e r m e n t a t i o n s o f S S L w i t h S cerevis iae i n t h e p r e s e n c e o f

    d i f f e r e n t x y l o s e i s o m e r a s e p r e p a r a t i o n s . B l a c k b a r = XI B ),

    s l a n t - l i n e d b a r - X I C ) , a n d g r a y b a r = X I D )

    t h e f e r m e n t a t i o n o f S S L . B a s e d o n t h e a b o v e r e s u lt s ,

    w e c h o s e

    S. cerevisiae

    f o r th i s i n v e s t i g a t i o n . T h e

    p r e v i o u s r e s u l t s h a d i n d i c a t e d t h a t t h e y i e l d c o u l d b e

    i m p r o v e d w i t h a b e t t e r e n z y m e , b e c a u s e (i ) q u i te l a r g e

    a m o u n t s o f s u g a r w e r e l e ft u n f e r m e n t e d a n d ( ii) w h e n

    u s i n g a l iq u i d f o r m o f X I ( A ) , th e e n z y m e w a s t o t a l l y

    i n a c t i v a t e d i n a N a C I s o l u t i o n w i t h a n i o n i c s t r e n g t h

    c o m p a r a b l e w i t h t h a t i n S S L . F u r t h e r m o r e , t h e m e t h -

    o d s a v a i l a b l e to m e a s u r e t h e x y l o s e i s o m e r a s e a c t i v it y

    i n S S L a r e n o t r e l i a b l e . A t t h e p r e s e n t t i m e t h i s c a n

    o n l y b e d o n e b y t a k in g a s a m p l e f r o m t h e f e r m e n t a t i o n

    a n d m e a s u r i n g t h e g l u c o s e i s o m e r a s e a c t i v i t y i n b u f -

    f e r , a c c o r d i n g t o G o n g

    et al.14

    T h i s m e t h o d d o e s n o t

    a c c o u n t f o r re v e r s i b l e d e a c t i v a t i o n in S S L . T h e e n -

    z y m e X I ( A ) i s a w h o l e c e l l p r e p a r a t i o n w h i c h c o n t a i n s

    e n z y m e t h a t m a y b e in a c t i v a t e d in S S L , b u t w h e n

    t r a n s f e r r e d t o b u f f e r g i v e s a s i g n i fi c a n t a c t i v i ty .

    B e c a u s e o f t h e s e n s i t i v i t y o f X I ( A ) t o h i g h s a l i n i ty ,

    w e i n v e s t i g a t e d t h e p e r f o r m a n c e o f t h r e e o t h e r e n -

    z y m e p r e p a r a t i o n s X I ( B , C , D )

    Figure 4).

    R e p e a t e d

    b a t c h f e r m e n t a t i o n s o f S S L w i t h

    S. cerevisiae,

    w h e r e

    w e a d d e d a n e x t r a 1 0 g I t x y l o s e , w e r e c h o s e n a s a n

    i n d ir e c t m e a s u r e o f e n z y m e p e r f o r m a n c e b e c a u s e o f

    t h e l a c k o f a d i re c t e n z y m e a c t iv i t y a s s a y . A l l e n z y m e

    p r e p a r a t i o n s w e r e i m m o b i l iz e d . E v e r y 2 4 h t h e y e a s t

    a n d t h e e n z y m e s w e r e s e p a r a t e d b y c e n t r i fu g a t i o n a n d

    t h e s u p e r n a t a n t w a s r e p l a c e d w i th n e w S S L . W e f o u n d

    a s m a l l d i f f e r e n c e i n y i e ld f a v o r i n g X I ( C ) . T h e c o n -

    t i n u o u s l y d e c r e a s i n g y i e l d i s p r o b a b l y d u e t o t h e

    d e a c t i v a t i o n o f t h e e n z y m e a n d t h e y e a s t . W e a l s o

    e s t i m a t e d t h e e n z y m e d e a c t i v a t i o n u s i n g th e m e t h o d

    o f G o n g et al. 14 Figure 5). A l s o a c c o r d i n g t o t h i s

    m e t h o d , t h e p r e p a r a t i o n X 1 ( C ) a p p e a r s s l ig h t l y m o r e

    s t a b l e t h a n t h e o t h e r t w o .

    Fermentat ion o f SSL and HF s traw

    In

    Figures 6

    a n d 7 a n d

    Table 2,

    w e h a v e s u m m a r i z e d

    t h e r e s u lt s f ro m t h e f e r m e n t a t i o n o f S S L a n d H F

    s t r a w w i t h

    S. cerevisiae

    a n d X I ( C ) i n t h e p r e s e n c e o f

    4 . 6 m M a z i d e . I n S S L 3 1 g 1 - 1 s u g a r w e r e c o n s u m e d

    and 16 .8 g l - ] e t h an o l , 1 .0 g 1-1 xy l i t o l , an d 2 .1 g 1

    g l y c e r o l w e r e p r o d u c e d . T h e y i e ld o f e t h a n o l b a s e d o n

    t o t a l s u g a r w a s 0 . 4 1 a n d o n c o n s u m e d s u g a r 0. 5 4 .

    A f t e r 6 8 . 5 h th e r e m a i n i n g s u g a r s c o n s i s t e d o f 4 . 3 g l -

    x y l o s e a n d 3 . 2 g l - ] g a l a c t o s e , w h i c h m e a n s t h a t 5 1 %

    o f t h e x y l o s e a n d 5 5 % o f t h e g a la c t o s e h a d b e e n

    u t i l i z e d . T h e g a l a c t o s e f e r m e n t a t i o n c a n p r o b a b l y b e

    i m p r o v e d w i t h a n a d a p t e d o r r e c y c l e d y e a s t , b e c a u s e

    t h e e n z y m e s r e s p o n s i b l e f o r g a l a c t o s e t r a n s p o r t a n d

    m e t a b o l i s m a r e i n d u c i b le .

    T h e f e r m e n t a t i o n o f t h e h y d r o g e n f l u o r i d e- p r e -

    t r e a t e d a n d a c i d - h y d r o l y s e d s t r a w r e s u l t e d i n a y i e ld o f

    e t h a n o l o f 0 . 4 0 , b a s e d o n t o t a l s u g a r s , a n d 0 . 4 5 , b a s e d

    o n c o n s u m e d s u g a rs . F r o m 3 7.1 g 1 t o f c o n s u m e d

    s u g a r s , 1 6 .8 g I ' e t h a n o l , 1 .9 g l - ] x y l i t o l , a n d 1 . 6 g I t

    g l y c e r o l w e r e p r o d u c e d . A f t e r 51 h f e r m e n t a t i o n , t h e

    1 0 0

    I ~ X l B )

    80 J ~ [ ] x l c)

    > ,

    ~ 60

    -~ 40

    g 2o

    o

    s t a r t 1 2 5

    B a t c h n o .

    F i g u r e G R e m a i n i n g g l u c o s e i s o m e r a s e a c t i v it y i n p e r c e n t o f

    i n i t i a l a c t i v i t y i n b u f f e r a f t e r b a t c h f e r m e n t a t i o n s 1 , 2 , a n d 5 in

    Figu re 4

    S a m e s y m b o l s a s in

    Figu re 4

    5 8 6 En zyme M ic r o b . Te ch n o l . , 1 98 9, vo l . 1 1, Se p te m b e r

  • 8/10/2019 Fermentation of Lignocellulose Hydrolysates With Yeasts and XylosIsomerase

    5/7

    T

    a

    e

    1

    S

    u

    c

    n

    s

    m

    p

    t

    o

    n

    ,

    p

    o

    f

    o

    r

    m

    a

    t

    o

    n

    ,

    a

    p

    r

    o

    d

    u

    c

    y

    e

    d

    i

    n

    t

    h

    e

    r

    m

    e

    n

    t

    a

    t

    o

    n

    o

    S

    S

    L

    w

    i

    h

    f

    v

    y

    s

    i

    n

    t

    h

    p

    e

    o

    x

    o

    s

    i

    s

    m

    e

    a

    X

    l

    A

    )

    a

    4

    6

    m

    M

    a

    d

    C

    o

    m

    e

    s

    M

    a

    E

    T

    O

    H

    X

    y

    o

    G

    l

    y

    o

    M

    a

    y

    e

    d

    E

    O

    H

    M

    a

    y

    e

    d

    E

    O

    H

    M

    a

    y

    e

    d

    E

    O

    H

    T

    m

    e

    Y

    e

    ~

    1

    1

    g

    1

    g

    1

    ~

    1

    g

    g

    1

    s

    o

    ~

    g

    1

    s

    c

    m

    e

    I

    g

    g

    1

    c

    s

    (

    h

    1 N

    C

    a

    d

    o

    c

    s

    2

    7

    9

    3

    4

    1

    8

    0

    2

    0

    3

    0

    1

    4

    P

    i

    c

    a

    s

    p

    s

    7

    6

    3

    0

    1

    5

    0

    1

    0

    9

    0

    0

    4

    P

    a

    e

    a

    u

    3

    5

    1

    9

    4

    6

    0

    1

    0

    1

    0

    0

    4

    S

    c

    z

    o

    m

    y

    p

    m

    b

    2

    1

    3

    0

    2

    0

    3

    0

    3

    0

    1

    4

    5

    S

    a

    o

    m

    y

    c

    e

    s

    a

    2

    1

    1

    1

    0

    2

    0

    0

    3

    0

    5

    0

    1

    4

    5

    S

    .

    c

    e

    s

    a

    +

    P

    .

    a

    u

    3

    1

    6

    5

    8

    2

    9

    0

    3

    0

    3

    0

    1

    4

    C

    -