Characterization of Recombinant Saccharomyces Cerevisiae Expressing a Mutated SPT15p Global Transcription Factor in Microaerobic Fermentations

The SPT15 gene encodes a Saccharomyces cerevisiae TATA-binding protein, which is able to globally control the transcription levels of various metabolic and regulatory genes. In this study, a SPT15 gene mutant (S42N, S78R, S163P and I212N) was expressed in S. cerevisiae BY4741 (SPT15-M3), of which effects on the yeast cell properties were evaluated in batch, fed-batch and simultaneous saccharification and fermentation (SSF) processes. Organic nitrogen sources and a microaerobic condition were more favorable for SPT15-M3 than the SPT15wt control in both cell growth and ethanol production. Fed-batch cultures of SPT15-M3 using concentrated glucose solution resulted in 9-19 % higher glucose consumption rate and ethanol productivity than those for SPT15wt. In addition, SPT15-M3 showed 3.9 and 4.5% increases in ethanol productivity from cassava hydrolysates and corn starch in SSF processes, respectively. It was concluded that overexpression of mutated SPT15 gene in S. cerevisiae would be a potent strategy to enhance ethanol production from glucose-based biomass.