Expression of Lactococcus lactis NADH oxidase increases 2,3-butanediol production in Pdc-deficient Saccharomyces cerevisiae

• Saccharomyces cerevisiae was engineered to produce 2,3-butanediol (2,3-BD).
• The engineered Pdc-deficient S. cerevisiae could grow on synthetic glucose medium.
• The small amount of ethanol supplemented greatly improved 2,3-BD formation.
• Expression of NADH oxidase substantially increased the 2,3-BD yield.

To minimize glycerol production during 2,3-BD fermentation by the engineered Saccharomyces cerevisiae, the Lactococcus lactis water-forming NADH oxidase gene (noxE) was expressed at five different levels. The expression of NADH oxidase substantially decreased the intracellular NADH/NAD+ ratio. The S. cerevisiae BD5_T2nox strain expressing noxE produced 2,3-BD with yield of 0.359 g 2,3-BD/g glucose and glycerol with 0.069 g glycerol/g glucose, which are 23.8% higher and 65.3% lower than those of the isogenic strain without noxE. These results demonstrate that the carbon flux could be redirected from glycerol to 2,3-BD through alteration of the NADH/NAD+ ratio by the expression of NADH oxidase.

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