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Enhanced xylose fermentation by engineered yeast expressing NADH oxidase through high cell density inoculums.
J Ind Microbiol Biotechnol. 2017 03; 44(3):387-395.JI

Abstract

Accumulation of reduced byproducts such as glycerol and xylitol during xylose fermentation by engineered Saccharomyces cerevisiae hampers the economic production of biofuels and chemicals from cellulosic hydrolysates. In particular, engineered S. cerevisiae expressing NADPH-linked xylose reductase (XR) and NAD+-linked xylitol dehydrogenase (XDH) produces substantial amounts of the reduced byproducts under anaerobic conditions due to the cofactor difference of XR and XDH. While the additional expression of a water-forming NADH oxidase (NoxE) from Lactococcus lactis in engineered S. cerevisiae with the XR/XDH pathway led to reduced glycerol and xylitol production and increased ethanol yields from xylose, volumetric ethanol productivities by the engineered yeast decreased because of growth defects from the overexpression of noxE. In this study, we introduced noxE into an engineered yeast strain (SR8) exhibiting near-optimal xylose fermentation capacity. To overcome the growth defect caused by the overexpression of noxE, we used a high cell density inoculum for xylose fermentation by the SR8 expressing noxE. The resulting strain, SR8N, not only showed a higher ethanol yield and lower byproduct yields, but also exhibited a high ethanol productivity during xylose fermentation. As noxE overexpression elicits a negligible growth defect on glucose conditions, the beneficial effects of noxE overexpression were substantial when a mixture of glucose and xylose was used. Consumption of glucose led to rapid cell growth and therefore enhanced the subsequent xylose fermentation. As a result, the SR8N strain produced more ethanol and fewer byproducts from a mixture of glucose and xylose than the parental SR8 strain without noxE overexpression. Our results suggest that the growth defects from noxE overexpression can be overcome in the case of fermenting lignocellulose-derived sugars such as glucose and xylose.

Authors+Show Affiliations

Carl R. Woese Institute for Genomic Biology, University of Illinois at Urbana-Champaign, 1206 W. Gregory Drive, Urbana, IL, 61801, USA. Department of Food Science and Human Nutrition, University of Illinois at Urbana-Champaign, Urbana, IL, 61801, USA.Department of Food Science and Human Nutrition, University of Illinois at Urbana-Champaign, Urbana, IL, 61801, USA.Carl R. Woese Institute for Genomic Biology, University of Illinois at Urbana-Champaign, 1206 W. Gregory Drive, Urbana, IL, 61801, USA. ysjin@illinois.edu. Department of Food Science and Human Nutrition, University of Illinois at Urbana-Champaign, Urbana, IL, 61801, USA. ysjin@illinois.edu.

Pub Type(s)

Journal Article

Language

eng

PubMed ID

28070721

Citation

Zhang, Guo-Chang, et al. "Enhanced Xylose Fermentation By Engineered Yeast Expressing NADH Oxidase Through High Cell Density Inoculums." Journal of Industrial Microbiology & Biotechnology, vol. 44, no. 3, 2017, pp. 387-395.
Zhang GC, Turner TL, Jin YS. Enhanced xylose fermentation by engineered yeast expressing NADH oxidase through high cell density inoculums. J Ind Microbiol Biotechnol. 2017;44(3):387-395.
Zhang, G. C., Turner, T. L., & Jin, Y. S. (2017). Enhanced xylose fermentation by engineered yeast expressing NADH oxidase through high cell density inoculums. Journal of Industrial Microbiology & Biotechnology, 44(3), 387-395. https://doi.org/10.1007/s10295-016-1899-3
Zhang GC, Turner TL, Jin YS. Enhanced Xylose Fermentation By Engineered Yeast Expressing NADH Oxidase Through High Cell Density Inoculums. J Ind Microbiol Biotechnol. 2017;44(3):387-395. PubMed PMID: 28070721.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Enhanced xylose fermentation by engineered yeast expressing NADH oxidase through high cell density inoculums. AU - Zhang,Guo-Chang, AU - Turner,Timothy L, AU - Jin,Yong-Su, Y1 - 2017/01/09/ PY - 2016/10/28/received PY - 2016/12/25/accepted PY - 2017/1/11/pubmed PY - 2017/12/12/medline PY - 2017/1/11/entrez KW - Ethanol KW - High initial cell density KW - Saccharomyces cerevisiae KW - Xylose fermentation KW - noxE SP - 387 EP - 395 JF - Journal of industrial microbiology & biotechnology JO - J Ind Microbiol Biotechnol VL - 44 IS - 3 N2 - Accumulation of reduced byproducts such as glycerol and xylitol during xylose fermentation by engineered Saccharomyces cerevisiae hampers the economic production of biofuels and chemicals from cellulosic hydrolysates. In particular, engineered S. cerevisiae expressing NADPH-linked xylose reductase (XR) and NAD+-linked xylitol dehydrogenase (XDH) produces substantial amounts of the reduced byproducts under anaerobic conditions due to the cofactor difference of XR and XDH. While the additional expression of a water-forming NADH oxidase (NoxE) from Lactococcus lactis in engineered S. cerevisiae with the XR/XDH pathway led to reduced glycerol and xylitol production and increased ethanol yields from xylose, volumetric ethanol productivities by the engineered yeast decreased because of growth defects from the overexpression of noxE. In this study, we introduced noxE into an engineered yeast strain (SR8) exhibiting near-optimal xylose fermentation capacity. To overcome the growth defect caused by the overexpression of noxE, we used a high cell density inoculum for xylose fermentation by the SR8 expressing noxE. The resulting strain, SR8N, not only showed a higher ethanol yield and lower byproduct yields, but also exhibited a high ethanol productivity during xylose fermentation. As noxE overexpression elicits a negligible growth defect on glucose conditions, the beneficial effects of noxE overexpression were substantial when a mixture of glucose and xylose was used. Consumption of glucose led to rapid cell growth and therefore enhanced the subsequent xylose fermentation. As a result, the SR8N strain produced more ethanol and fewer byproducts from a mixture of glucose and xylose than the parental SR8 strain without noxE overexpression. Our results suggest that the growth defects from noxE overexpression can be overcome in the case of fermenting lignocellulose-derived sugars such as glucose and xylose. SN - 1476-5535 UR - https://www.unboundmedicine.com/medline/citation/28070721/Enhanced_xylose_fermentation_by_engineered_yeast_expressing_NADH_oxidase_through_high_cell_density_inoculums_ L2 - http://dx.doi.org/10.1007/s10295-016-1899-3 DB - PRIME DP - Unbound Medicine ER -