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Effects of xylitol dehydrogenase ( XYL2 ) on xylose fermentation by engineered Candida glycerinogenes
Author(s) -
Zong Hong,
Zhang Cheng,
Zhuge Bin,
Lu Xinyao,
Fang Huiying,
Sun Jin
Publication year - 2017
Publication title -
biotechnology and applied biochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.468
H-Index - 70
eISSN - 1470-8744
pISSN - 0885-4513
DOI - 10.1002/bab.1514
Subject(s) - xylitol , xylose , fermentation , chemistry , pichia stipitis , biochemistry , glycerol , erythritol , xylose metabolism
Efficient bioconversion of d ‐xylose into various biochemicals is critical for lignocelluloses application. Candida glycerinogenes , expressing the xylitol dehydrogenase ( XYL2 ) gene, has the ability to produce glycerol from xylose entered into pentose phosphate pathway. In this study, we demonstrate that low expression levels of the XYL2 gene derived from Scheffersomyces stipitis in C. glycerinogenes is a major bottleneck in efficient xylose fermentation. Through a metabolic engineering approach using an integrative expression, XYL2 was identified as an overexpression target for improving xylose metabolism. Two recombinant strains with XYL2 overexpression were constructed to ferment a mixture of glucose and xylose simultaneously in batch fermentation. Compared with C. glycerinogenes (wild type), glycerol production from xylose by C. glycerinogenes (PURGAPX2) and C. glycerinogenes (PURGPDX2) was increased by 94.5% and 103.3%, respectively. It was also found that additional overexpression of XYL2 under the control of strong promoters in a xylose‐fermenting strain not only reduced xylitol accumulation but also increased glycerol yields. As the expression levels of XYL2 increased, the glycerol yields gradually improved from 30.6 to 63.3 g/L, whereas the xylitol yields significantly decreased from 38.7 to 19.9 g/L. These results suggest that strong expression of XYL2 is a necessary condition for developing efficient xylose‐fermenting strains.