title: Rapid ethanol production at elevated temperatures by engineered thermotolerant Kluyveromyces marxianus via the NADP(H)-preferring xylose reductase-xylitol dehydrogenase pathway.
abstract: Conversion of xylose to ethanol by yeasts is a challenge because of the redox imbalances under oxygen-limited conditions. The thermotolerant yeast Kluyveromyces marxianus grows well with xylose as a carbon source at elevated temperatures, but its xylose fermentation ability is weak. In this study, a combination of the NADPH-preferring xylose reductase (XR) from Neurospora crassa and the NADP(+)-preferring xylitol dehydrogenase (XDH) mutant from Scheffersomyces stipitis (Pichia stipitis) was constructed. The xylose fermentation ability and redox balance of the recombinant strains were improved significantly by over-expression of several downstream genes. The intracellular concentrations of coenzymes and the reduced coenzyme/oxidized coenzyme ratio increased significantly in these metabolic strains. The byproducts, such as glycerol and acetic acid, were significantly reduced by the disruption of glycerol-3-phosphate dehydrogenase (GPD1). The resulting engineered K. marxianus YZJ088 strain produced 44.95 g/L ethanol from 118.39 g/L xylose with a productivity of 2.49 g/L/h at 42 °C. Additionally, YZJ088 realized glucose and xylose co-fermentation and produced 51.43 g/L ethanol from a mixture of 103.97 g/L xylose and 40.96 g/L glucose with a productivity of 2.14 g/L/h at 42 °C. These promising results validate the YZJ088 strain as an excellent producer of ethanol from xylose through the synthetic xylose assimilation pathway.
authors.affiliation: School of Life Science, University of Science and Technology of China, Hefei, Anhui 230027, PR China; Hefei National Laboratory for Physical Science at the Microscale, Hefei, Anhui 230026, PR China.
authors.forename: Jia
authors.initials: J
authors.lastname: Zhang
authors.affiliation: School of Life Science, University of Science and Technology of China, Hefei, Anhui 230027, PR China; Hefei National Laboratory for Physical Science at the Microscale, Hefei, Anhui 230026, PR China.
authors.forename: Biao
authors.initials: B
authors.lastname: Zhang
authors.affiliation: School of Life Science, University of Science and Technology of China, Hefei, Anhui 230027, PR China; Hefei National Laboratory for Physical Science at the Microscale, Hefei, Anhui 230026, PR China.
authors.forename: Dongmei
authors.initials: D
authors.lastname: Wang
authors.affiliation: School of Life Science, University of Science and Technology of China, Hefei, Anhui 230027, PR China; Department of Biology and Biochemistry, University of Houston, Houston, TX 77004-5001, USA; Hefei National Laboratory for Physical Science at the Microscale, Hefei, Anhui 230026, PR China.
authors.forename: Xiaolian
authors.initials: X
authors.lastname: Gao
authors.affiliation: School of Life Science, University of Science and Technology of China, Hefei, Anhui 230027, PR China; Hefei National Laboratory for Physical Science at the Microscale, Hefei, Anhui 230026, PR China.
authors.forename: Lianhong
authors.initials: L
authors.lastname: Sun
authors.affiliation: School of Life Science, University of Science and Technology of China, Hefei, Anhui 230027, PR China; Hefei National Laboratory for Physical Science at the Microscale, Hefei, Anhui 230026, PR China. Electronic address: hjiong@ustc.edu.cn.
authors.forename: Jiong
authors.initials: J
authors.lastname: Hong
mesh_terms: D050542:D-Xylulose Reductase / Q000235:genetics*; D004795:Enzyme Stability; D000431:Ethanol / Q000378:metabolism*; D005285:Fermentation; D005947:Glucose / Q000378:metabolism; D007716:Kluyveromyces / Q000235:genetics / Q000378:metabolism*; D060847:Metabolic Engineering; D053858:Metabolic Networks and Pathways; D009249:NADP / Q000378:metabolism*; D060888:Real-Time Polymerase Chain Reaction; D013696:Temperature; D014994:Xylose / Q000378:metabolism
chemical_list: D000431:Ethanol; D009249:NADP; D014994:Xylose; D050542:D-Xylulose Reductase; D005947:Glucose
keywords: Co-assimilation; Elevated temperature; Kluyveromyces marxianus; NADP(+)-preferring xylitol dehydrogenase; NADPH-preferring xylose reductase