Effects of systematic overexpression of genes involved in the non-oxidative pentose phosphate pathway on xylose metabolism of recombinant Saccharomyces cerevisiae strains

Abstract:

[Objective] Construction of highly efficient xylose-utilizing Saccharomyces cerevisiae strains by single, double or multiple overexpression of genes involved in the non-oxidative pentose phosphate (PP) pathway. [Methods] TAL1, TKL1, RPE1 and RKI1 under the control of different strong promoters were integrated either alone or in combination into the xyloses-fermenting recombinant yeast strain AYHNEW2. The fermentation performances of the resulting strains were studied on 5% xylose. [Results] The recombinant strains generated with our approach showed improved xylose fermentation performance with varying degrees. The best results were obtained by simultaneous overexpression of all the non-oxidative PP pathway genes, and compared to the reference strain AYHNEW2, the strain resulted from this genetic modification showed a 39.25% and 12.57% increase in ethanol productivity and yield, respectively. [Conclusion] Previous studies for enhancing xylose fermentation rate by genetic modification of the non-oxidative PP pathway had been more focused on overexpression of the individual genes in the pathway. In this work, we demonstrated that, compared to single or partial over-expression of the non-oxidative PP pathway, simultaneous overexpression of all the genes in the pathway was more effective in increasing the rate of carbon flow from xylose to ethanol.

Key words:Saccharomyces cerevisiae, Non-oxidative pentose phosphate pathway, Xylose, Ethanol