Enhanced expression of the codon-optimized exo-inulinase gene from the yeast Meyerozyma guilliermondii in Saccharomyces sp. W0 and bioethanol production from inulin

In the present study, after the exo-inulinase gene INU1 from Meyerozyma guilliermondii was optimized according to the codon usage bias of Saccharomyces cerevisiae, both the optimized gene INU1Y and the native gene INU1 were ligated into the homologous integration expression vector pMIRSC11 and expressed in Saccharomyces sp. W0. It was determined that the inulinase activity of the recombinant yeast Y13 with the optimized gene INU1Y was 43.84 U/mL, which was obviously higher than that (31.39 U/mL) produced by the recombinant yeast EX3 with the native gene INU1. Moreover, it was indicated that the recombinant yeast Y13 could produce 126.30 mg/mL ethanol from 300.0 g/L inulin while the recombinant yeast EX3 and Saccharomyces sp. W0 produced 122.75 mg/mL and 114.15 mg/mL ethanol, respectively, under the same conditions. In addition, the ethanol productivity of the recombinant yeast Y13 was 2.25 mg/mL/h within 48 h of the fermentation, which was obviously higher than that of the recombinant yeast EX3 (1.97 mg/mL/h) and Saccharomyces sp. W0 (1.77 mg/mL/h) within the same period. The results demonstrated that the recombinant yeast Y13 had higher ethanol production and productivity than the recombinant yeast EX3 and Saccharomyces sp. W0. Therefore, it was concluded that the codon optimization of the exo-inulinase gene from M. guilliermondii effectively enhanced inulinase activity and improved ethanol production from inulin by Saccharomyces sp. W0 carrying the optimized inulinase gene.