Overexpression of Endogenous Xylose Reductase Enhanced Xylitol Productivity at 40 °C by Thermotolerant Yeast Kluyveromyces marxianus
Applied Biochemistry and Biotechnology(2019)
摘要
Xylitol is a valuable substance utilized by food and biochemical industries. NAD(P)H-dependent xylose reductase (XR)—encoded by the yeast KmXYL1 gene—is the key enzyme which facilitates reduction of xylose to xylitol. Multi-copy integration of a mutant KmXYL1 ( mKmXYL1 ) gene was carried out using thermotolerant yeast Kluyveromyces marxianus KCTC17555 ΔURA3 , in order to enhance xylitol production. After multi-copy integration, the highest xylitol producing strain was isolated and named K. marxianus 17555-JBP2. This strain exhibited 440% higher xylitol production than the parental strain at 30 °C. Due to a multi-copy integration of the mKmXYL1 gene, various additional differences between K. marxianus 17555-JBP2 and the parental strain were observed, including a 66% increase in NAD(P)H-dependent XR activity at high temperature (45 °C). Quantitative real-time PCR and transcriptome analysis demonstrated that, relative to the parent strain, K. marxianus 17555-JBP2 exhibited two more copies of mKmXY1 genes and a 9.63-fold elevation in transcription of NAD(P)H-dependent XR. After optimization of bioreactor fermentation conditions (agitation speed), high-temperature (40 °C) xylitol productivity of K. marxianus 17555-JBP2 exhibited an 81% improvement relative to the parental strain. In this study, we demonstrated that the overexpression of endogenous XR could enhance xylitol productivity at 40 °C by thermotolerant K. marxianus .
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关键词
Kluyveromyces marxianus,Thermotolerant,mKmXYL1,Xylose reductase
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