Regulation of thiamine synthesis in Saccharomyces cerevisiae for improved pyruvate production.

Metabolic engineering of Saccharomyces cerevisiae for high-yield production of carboxylic acid requires a cytosolic pyruvate pool as precursor. In this study, a novel strategy to improve pyruvate production and reduce metabolic by-products via regulating thiamine synthesis was explored. Two of the thiamine biosynthesis regulatory genes, THI2 and THI3, were disrupted in the S. cerevisiae parent strain FMME-002. The mutants FMME-002ΔTHI2 and FMME-002ΔTHI3 both exhibited an enhanced pyruvate yield. Moreover, FMME-002ΔTHI2 achieved a relatively higher pyruvate production, and the highest concentration of pyruvate was achieved when 0.04 µ m thiamine was added. Enzyme assays and fermentation profiles of the THI2-complemented strain indicated that the observed metabolic changes represented intrinsic effects of THI2 deletion on the physiology of S. cerevisiae. Under optimal C:N ratio conditions, FMME-002ΔTHI2 produced pyruvate up to 8.21 ± 0.30 g/l, whereas the ethanol titre decreased to 2.21 ± 0.24 g/l after 96 h of cultivation. These results demonstrate the possibility of improving pyruvate production by regulating thiamine synthesis in S. cerevisiae.