Introduction of heterogeneous NADH reoxidation pathways into Torulopsis glabrata significantly increases pyruvate production efficiency

The aim of this study was to increase pyruvate production efficiency in a multi-vitamin auxotrophic yeast, Torulopsis glabrata. This was achieved by decreasing intracellular NADH content through the introduction of two different NADH reoxidation pathways: one in the cytoplasm and the other in mitochondria A nox (encoding a cytoplasmic H2O-forming NADH oxidase) and an AOXI (encoding a mitochondrial alternative oxidase) were successfully expressed heterologously in T. glabrata, resulting in a decrease in the NADH and ATP contents of 55% and 26%, (in T. glabrata NOX) and 45% and 47% (in T. glabrata AOX), respectively. The decreases in nucleotide concentrations led to increases in the glucose consumption rate, the pyruvate yield and pyruvate productivity of 27%, 15% and 22% (in T. glabrata NOX) and 38%, 21%, and 29% (in T. glabrata AOX), respectively, compared with the corresponding values of the control. We conclude that this method provides an alternative way to enhance the production efficiency of NADH-related metabolites.