In this study, the xylose reductase gene (XRTL) from Thermomyces lanuginosus SSBP was expressed in Pichia pastoris GS115 and Saccharomyces cerevisiae Y294. The purified 39.2 kDa monomeric enzyme was optimally active at pH 6.5 and 50 °C and showed activity over a wide range of temperatures (30-70 °C) and pH (4.0-9.0), with a half-life of 1386 min at 50 °C. The enzyme preferred NADPH as cofactor and showed broad substrate specificity. The enzyme was inhibited by Cu2+, Fe2+ and Zn2+, while ferulic acid was found to be the most potent lignocellulosic inhibitor. Recombinant S. cerevisiae with the XRTL gene showed 34% higher xylitol production than the control strain. XRTL can therefore be used in a cell-free xylitol production process or as part of a pathway for utilization of xylose from lignocellulosic waste.
Keywords: Ferulic acid; Lignocellulose; Thermomyces lanuginosus; Xylitol; Xylose reductase.
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