Arabinose fermentation

Speakers were asked to provide quantitative data on the performance of different xylose- (or, in one instance, arabinose-) fermenting strains in laboratory media and, where possible, in "industrial" media prepared by hydrolysis of native lignocellulosic substrates. The data provided are presented in Table 1, which gives an indication of the performance of the various strains but should not be taken as a rigorous comparison. In particular, there is considerable variation in the extent of nutritional supplementation of the various media and the degree of detoxification of the hydrolysates. References provided by some of the speakers are also given (1-6). 

Data supplied by J. Becker and E. Boles arabinose fermenting strain. 

Deanda, K., Zhang, M., Eddy, C., Picataggio, S. (1996) Development of an arabinose-fermenting Zymomonas mobilis strain by metabolic pathway engineering. Appl. Environ. Microbiol. 62,4465 1470. 

Mohagheghi A, Evans K, Chou YC, Zhang M. (2002). Cofermentation of glucose, xylose, and arabinose by genomic DNA-integrated xylose/arabinose fermenting strain of Zymomonas mobilis AXIOI. Appl Biochem Biotechnol, 98-100, 885-898. 

Recombinant Saccharomyees cerevisiae, able to ferment the pentoses D-xylose and L-arabinose, was modified for improved fermentation rates and yields. Pentose fermentation is relevant when low cost raw materials such as plant hydrolysates are fermented to ethanol. The two most widespread pentose sugars in our biosphere are D-xylose and L-arabinose. S. cerevisiae is unable to ferment pentoses but has been engineered to do so however rates and yields are low. The imbalance of redox cofactors (excess NADP and NADH are produced) is considered a major limiting factor. For the L-arabinose fermentation we identified an NADH-dependent L-xylulose reductase replacing the previously known NADPH-dependent enzyme. For D-xylose fermentation we introduced an NADP-dependent glyceraldehyde 3-phospate dehydrogenase to regenerate NADPH. 

Information about the L-arabinose pathway in yeast is rare. It is probably similar to the mold pathway. It requires a xylitol dehydrogenase as shown by Shi et al. 24). In a mutant of Pichia stipitis, which was unable to grow on L-arabinose, overexpression of a xylitol dehydrogenase could restore growth on L-arabinose. In a study of Dien et al. (5) more than 100 yeast species were tested for L-arabinose fermentation. Most of them produced arabinitol and xylitol indicating that the yeast pathway is indeed similar to the pathway of molds and not to the pathway of bacteria. There is only little knowledge of the enzymes in the yeast pathway. Aldose reductases which are active with L-arabinose and D-xylose were described e.g. for the yeasts S. cerevisiae 25) and P. stipitis 17). The enzymes have similar affinity toward D-xylose and L-arabinose and convert both sugars with a similar rate. The S. cerevisiae enzyme however is strictly NADPH-dependent, while the P. stipitis enzyme can use both NADH and... 

Kurtzman C, Dien B (1998) Candida arabinofermentans, a new L-arabinose fermenting yeast. Antonie Van Leeuwenhoek 74(4) 237-243... 

For the expression of PAMO-P3, 100 mL of an overnight preculture of E. coli TOPIO [pPAMO-P3] in terrific broth medium supplemented with 100 mg of carbenicillin was used to inoculate 5 L terrific broth medium supplemented with 100 mg of carbenicillin and 0.1 % L-arabinose in a 5 L fermenter. The expression was carried out... 

For monitoring the extent of polysaccharide hydrolysis, l.c. methods that sepeu ate and analyze the non-fermentable oligosaccharides (d.p. 3-30) derived from cellulose, hemicellulose, and pectins are useful, and have already been described (see Section III,l,c). For determination of the monosaccharide composition of completely hydrolyzed, plant polysaccharides, l.c. is especially useful and has been applied to the compositional analysis of hydrolyzed plant fiber,wood pulps,plant cell-walls,and cotton fibers.In these representative examples, the major sugars of interest, namely, glucose, xylose, galactose, arabinose, and mannose, have traditionally been difficult to resolve by l.c. The separa-... 

Numerous investigations concerning the mechanism of these reductive fermentations have been reported. Basically it is important that pentoses (u-arabinose and D-xylose) yield the same products of fermenta-... 

Important results have recently been obtained by Simon. Among other things he ascertained that glycerol yields butyric acid. The formation of four-carbon compounds from six-carbon substrates is independent of the grouping (aldehyde, hydroxyl, carboxyl, phosphory-lated hydroxyl) at the first carbon atom of the molecule. L-Rhamnose and D-arabitol are fermented, but not n-arabinose and D-sorbitol. In contrast to the studies of Underkofler and Hunter, " L-sorbose has been found fermentable. Results obtained with fresh and acetone-dried Cl. hutylicum are identical in principle. 

Rates of hydrolysis are given in pmol of arabinose produced per minute per mg of protein. (35) O. Yoshihara and A. Kaji, Abstr. Int. Ferment Symp., 4th, (Kyoto), (1972) p. 241. 

Hydrolysate B from corn stover contained 4 g/L of glucose, 17.9 g/L of xylose, 5 g/L of arabinose, and 2.5 g/L of acetic acid. Glucose was readily fermented eighty-three percent of xylose was fermented in 23 h. The production of ethanol by fermentation of the com stover hydrolysate was 9 g/L (Fig. 3). The yield of ethanol from consumed sugars reached 93% of theoretical yield. We did not observe xylitol production and acetic acid consumption. 

Sixty-five percent of the carbohydrates present in QF are in the form of pentoses, which S. cerevisiae does not ferment to ethanol. We have developed a recombinant E. coli strain that is capable of fermenting arabinose,... 

Fig. 3. (A) SSF of pretreated DWG with S. cerevisiae. Fermentations were performed in duplicate. (B) Fermentation of DWG liquid hydrolysate with E. coli FBR5. Fermentations were performed in duplicate. (A) Xylose ( ) glucose ( ) arabinose ( ) ethanol.

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