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Title:Improved xylose fermentation by expression of a putative xylose transporter encoding gene HXT2.4 in Saccharomyces cerevisiae
Author(s):Kuanyshev, Nurzhan
Advisor(s):Jin, Yong-Su
Department / Program:Food Science & Human Nutrition
Discipline:Food Science & Human Nutrition
Degree Granting Institution:University of Illinois at Urbana-Champaign
Saccharomyces cerevisiae
sugar transporter
Scheffersomyces stipitis
Abstract:Saccharomyces cerevisiae is considered one of the promising microorganisms in lignocellulosic bioethanol production. Unfortunately S. cerevisiae cannot consume xylose, a pentose sugar which comprises almost 30% of lignocellulosic biomass. Metabolic and genetic engineering methods were used to develop S. cerevisiae that could consume xylose. However in S. cerevisiae, pentose sugars can only enter the cell through native hexose transporters which have two orders of magnitude lower affinities toward pentose sugar than hexose sugar. Thus pentose uptake is a limiting step in xylose fermentation using S. cerevisiae. In order to solve this problem, we introduced putative xylose transporter gene HXT2.4 from natural xylose consuming Scheffersomyces stipitis into engineered xylose consuming S. cerevisiae. Xylose consumption by the HXT2.4 expressing S. cerevisiae was tested through fermentation. To prove that HXT2.4 indeed enhanced the flux of xylose into the yeast cell, intracellular xylose and xylitol concentrations were measured using 100% methanol quenching and extraction. The results showed that the HXT2.4 expressing S. cerevisiae could accumulate 10% more xylose and 40% more xylitol than the control strain. Sugar uptake kinetic parameters were determined using 14C-labeled xylose. The results showed higher Vmax of HXT2.4 expressing S. cerevisiae than control strain. Introduction of HXT2.4 may improve xylose fermentation by engineered S. cerevisiae depending on strain background. More efficient transport of pentose sugar can improve the utilization of xylose, which will allow the development of an efficient xylose fermenting S. cerevisiae for the production of bioethanol from lignocellulose.
Issue Date:2013-05-24
Rights Information:Copyright 2013 Nurzhan Kuanyshev
Date Available in IDEALS:2013-05-24
Date Deposited:2013-05

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