title: Production of Xylitol from D-Xylose by Overexpression of Xylose Reductase in Osmotolerant Yeast Candida glycerinogenes WL2002-5.
abstract: Efficient bioconversion of D-xylose into various biochemicals is critical for the developing lignocelluloses application. In this study, we compared D-xylose utilization in Candida glycerinogenes WL2002-5 transformants expressing xylose reductase (XYL1) in D-xylose metabolism. C. glycerinogenes WL2002-5 expressing XYL1 from Schefferomyces stipitis can produce xylitol. Xylitol production by the recombinant strains was evaluated using a xylitol fermentation medium with glucose as a co-substrate. As glucose was found to be an insufficient co-substrate, various carbon sources were screened for efficient cofactor regeneration, and glycerol was found to be the best co-substrate. The effects of glycerol on the xylitol production rate by a xylose reductase gene (XYL1)-overexpressed mutant of C. glycerinogenes WL2002-5 were investigated. The XYL1-overexpressed mutant produced xylitol from D-xylose using glycerol as a co-substrate for cell growth and NAD (P) H regeneration: 100 g/L D-xylose was completely converted into xylitol when at least 20 g/L glycerol was used as a co-substrate. XYL1 overexpressed mutant grown on glycerol as co-substrate accumulated 2.1-fold increased xylitol concentration over those cells grown on glucose as co-substrate. XYL1 overexpressed mutant produced xylitol with a volumetric productivity of 0.83 g/L/h, and a xylitol yield of 98 % xylose. Recombinant yeast strains obtained in this study are promising candidates for xylitol production. This is the first report of XYL1 gene overexpression of C. glycerinogenes WL2002-5 for enhancing the efficiency of xylitol production.
authors.affiliation: The Key Lab of Industrial Biotechnology of Ministry of Education, Research Centre of Industrial Microorganisms, School of Biotechnology, Jiangnan University, Wuxi Jiangsu Province, 214122, People's Republic of China.
authors.forename: Cheng
authors.initials: C
authors.lastname: Zhang
authors.forename: Hong
authors.initials: H
authors.lastname: Zong
authors.forename: Bin
authors.initials: B
authors.lastname: Zhuge
authors.forename: Xinyao
authors.initials: X
authors.lastname: Lu
authors.forename: Huiying
authors.initials: H
authors.lastname: Fang
authors.forename: Jian
authors.initials: J
authors.lastname: Zhuge
mesh_terms: D000222:Adaptation, Physiological / Q000187:drug effects; D000449:Aldehyde Reductase / Q000378:metabolism*; D002175:Candida / Q000187:drug effects / Q000201:enzymology* / Q000235:genetics; D004591:Electrophoresis, Polyacrylamide Gel; D005285:Fermentation / Q000187:drug effects; D005453:Fluorescence; D018628:Gene Dosage; D005800:Genes, Fungal; D005947:Glucose / Q000378:metabolism; D005990:Glycerol / Q000494:pharmacology; D007700:Kinetics; D009995:Osmosis / Q000187:drug effects; D060888:Real-Time Polymerase Chain Reaction; D011995:Recombination, Genetic / Q000235:genetics; D012015:Reference Standards; D013379:Substrate Specificity / Q000187:drug effects; D013997:Time Factors; D014993:Xylitol / Q000096:biosynthesis*; D014994:Xylose / Q000096:biosynthesis*
chemical_list: D014994:Xylose; D000449:Aldehyde Reductase; D005947:Glucose; D005990:Glycerol; D014993:Xylitol