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KMID : 0613820160260121376
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Journal of Life Science
2016 Volume.26 No. 12 p.1376 ~ p.1382
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Secretory Expression System of Xylose Reductase (GRE3) for Optimal Production of Xylitol
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Jung Heo-Myung
Kim Jae-Woon
Kim Yeon-Hee
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Abstract
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Xylitol is widely used in the food and medical industry. It is produced by the reduction of xylose (lignocellulosic biomass) in the Saccharomyces cerevisiae strain, which is considered genetically safe. In this study, the expression system of the GRE3 (YHR104W) gene that encodes xylose reductase was constructed to efficiently produce xylitol in the S. cerevisiae strain, and the secretory production of xylose reductase was investigated. To select a suitable promoter for the expression of the GRE3 gene, pGMF-GRE3 and pAMF-GRE3 plasmid with GAL10 promoter and ADH1 promoter, respectively, were constructed. The mating factor α (MFα) signal sequence was also connected to each promoter for secretory production. Each plasmid was transformed into S. cerevisiae SEY2102△trp1, and SEY2102△trp1/pGMF- GRE3 and SEY2102△trp1/pAMF-GRE3 transformants were selected. In the SEY2102△trp1/pGMF-GRE3 strain, the total activity of xylose reductase reached 0.34 unit/mg-protein when NADPH was used as a cofactor; this activity was 1.5 fold higher than that in SEY2102△trp1/ pAMF-GRE3 with ADH1 as the promoter. The secretion efficiency was 91% in both strains, indicating that most of the recombinant xylose reductase was efficiently secreted in the extracellular fraction. In a baffled flask culture of the SEY2102△trp1/pGMF-GRE3 strain, 12.1 g/l of xylitol was produced from 20 g/l of xylose, and ~83% of the consumed xylose was reduced to xylitol.
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KEYWORD
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Promoter strength, Saccharomyces cerevisiae, secretion production, xylitol productivity, xylose reductase
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