Enhanced bioethanol production by recombinant Saccharomyces cerevisiae ETS3 transformed with a mutated SPT15 gene

Global transcription machinery engineering (gTME) is deviced by introduction of the SPT15 variants encoding Saccharomyces cerevisiae TATA-binding proteins. By gTME, recombinant S. cerevisiae ETS3 had been selected to possess high ethanol production ability under high osmotic pressure. In this study, the robustness of the ETS3 strain was evaluated by batch and fed-batch fermentation techniques using high glucose concentration under different aeration conditions. A batch culture of ETS3 with 300 g/L glucose at oxygen-limited condition resulted in 22.2 g/L dry cell mass, 98.1 g/L ethanol concentration and 1.82 g/L-h ethanol productivity which were about 13-16% increases relative to those of S. cerevisiae BY4741. A micro-aerobic condition elevated the ethanol productivity to 2.49 g/L-h without significant changes of other fermentation parameters. In fed-batch fermentation with 400 g/L glucose, ETS3 produced up to 151.7 g/L ethanol and showed a maximum yield of 0.402g ethanol/g glucose. In comparison to the host strain, ETS3 showed a 23% increase in dry cell mass. It was certain that gTME was a useful tool to confer enhanced fermentative properties against osmotic pressure to S. cerevisiae.