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Title: Fermentation kinetics for xylitol production by a Pichia stipitis D-xylulokinase mutant previously grown in spent sulfite liquor

Author: Rodrigues, Rita C.L.B.; Lu, Chenfeng; Liu, Bernice; Jeffries, Thomas W.;

Date: 2008

Source: Applied biochemistry and biotechnology. Vol. 148, no. 2 (2008): pages 199-209.

Publication Series: Miscellaneous Publication

Description: Spent sulfite pulping liquor (SSL) contains lignin, which is present as lignosulfonate, and hemicelluloses that are present as hydrolyzed carbohydrates. To reduce the biological oxygen demand of SSL associated with dissolved sugars, we studied the capacity of Pichia stipitis FPL-YS30 (xyl3[delta]) to convert these sugars into useful products. FPL-YS30 produces a negligible amount of ethanol while converting xylose into xylitol. This work describes the xylose fermentation kinetics of yeast strain P. stipitis FPL-YS30. Yeast was grown in rich medium supplemented with different carbon sources: glucose, xylose, or ammonia-base SSL. The SSL and glucose-acclimatized cells showed similar maximum specific growth rates (0.146 h−1). The highest xylose consumption at the beginning of the fermentation process occurred using cells precultivated in xylose, which showed relatively high specific activity of glucose-6-phosphate dehydrogenase (EC 1.1.1.49). However, the maximum specific rates of xylose consumption (0.19 gxylose/gcel h) and xylitol production (0.059 gxylitol/gcel h) were obtained with cells acclimatized in glucose, in which the ratio between xylose reductase (EC 1.1.1.21) and xylitol dehydrogenase (EC 1.1.1.9) was kept at higher level (0.82). In this case, xylitol production (31.6 g/l) was 19 and 8% higher than in SSL and xylose-acclimatized cells, respectively. Maximum glycerol (6.26 g/l) and arabitol (0.206 g/l) production were obtained using SSL and xylose-acclimatized cells, respectively. The medium composition used for the yeast precultivation directly reflected their xylose fermentation performance. The SSL could be used as a carbon source for cell production. However, the inoculum condition to obtain a high cell concentration in SSL needs to be optimized.

Keywords: Xylitol, yeast, xylose, ammonia spent sulfite liquor-SSL, inoculum adaptation, enzymes, glucose, chemical kinetics, sulfite waste liquor, microbiology, fungi, biotechnology, wood-decaying fungi, alcohol, yeast fungi, fermentation, microbial metabolism, industrial applications, sulfite liquors, kenetics, D-xylulokinase, ethanol, Pichia stipitis, decay fungi

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  • This article was written and prepared by U.S. Government employees on official time, and is therefore in the public domain.

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Rodrigues, Rita C.L.B.; Lu, Chenfeng; Liu, Bernice; Jeffries, Thomas W. 2008. Fermentation kinetics for xylitol production by a Pichia stipitis D-xylulokinase mutant previously grown in spent sulfite liquor. Applied biochemistry and biotechnology. Vol. 148, no. 2 (2008): pages 199-209.

 


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