Heterologous expression of H2O-forming NADH oxidase in Torulopsis glabrata significantly enhance the pyruvate productivity of the host

Abstract:

[Objective] The aim of this manuscript was to illuminate the effect of NADH oxidation pathway on the glycolytic rate and the pyruvate productivity. [Methods] The noxE gene encoding a water-forming NADH oxidase from Lactococcus lactis, was expressed in a pyruvate producing Torulopsis glabrata CCTCC M202019. A mutant strain T. glabrata-PDnoxE, with specific NADH oxidase activity of 34.8 U/mg protein, was obtained. [Results] During batch fermentation with 100 g/L glucose in the medium, the dry cell weight, the glucose consumption rate and pyruvate production rate were 168%, 44.9% and 12% higher than that of the parent strain, respectively. Only 2.5 g/L residual glucose was detected in the fermentation broth after 36 h culture, then 50 g/L glucose was supplemented to the culture broth and the concentration of pyruvate increased to 67.2 g/L. As the result of NADH oxidase overexpression, the intracellular NADH, NAD+ and ATP concentrations of the mutant and the parent strain were determined, the NADH and ATP content decreased 18.1% and 15.8% respectively, while the NAD+ concentration increased 11.1%. [Conclusion] The increasing of intracellular NAD+ concentration can efficiently enhance the rate of glucose consumption and the pyruvate production.