Engineering the pentose phosphate pathway of Saccharomyces cerevisiae for production of ethanol and xylitol

摘要: The baker’s yeast Saccharomyces cerevisiae has a long tradition in alcohol production from D-glucose of e.g. starch. However, without genetic modifications it is unable to utilise the 5-carbon sugars D-xylose and L-arabinose present plant biomass. In this study, one key metabolic step catabolic pathway recombinant D-xylose-utilising S. strains was studied. This step, carried out by xylulokinase (XK), shown be rate-limiting, because overexpression xylulokinase-encoding gene XKS1 increased both specific ethanol rate yield D-xylose. addition, less unwanted side product xylitol produced. Recombinant D-xylose-utilizing have been constructed expressing genes coding for first two enzymes pathway, reductase (XR) dehydrogenase (XDH) Pichia stipitis. ability endogenous enable utilisation evaluated. Overexpression GRE3 an unspecific aldose ScXYL2 homologue enabled growth on aerobic conditions. strain with had lower accumulated more compared corresponding P. Use strictly NADPH-dependent Gre3p instead stipitis XR able NADH NADPH leads severe redox imbalance. not engineered presence activity expression SOR1 or SOR2 sorbitol dehydrogenase. Thus, activities encoded possibly SOR2, feasible, but requires efficient balance engineering.