Ethanol production and fermentation characteristics of recombinant Saccharomyces cerevisiae strains grown on starch

摘要

The production of ethanol from starch has been investigated in three genetically modified Saccharomyces cerevisiae strains (YPG/AB, YPG/MM, and YPB-G). Two of the three strains produce the Aspergillus awamori glucoamylase together with either the Bacillus subtilis (YPG/AB) or the mouse (YPG/MM) alpha-amylase as separately secreted polypeptides. YPB-G, on the other hand, secretes a bifunctional fusion, protein that contains both the B. subtilis alpha-amylase and the A. awamori glucoamylase activities. Substrate utilization, biomass growth, and ethanol production were all studied in both starch- and glucose-containing media. Much higher growth rates were found when any of the three strains were grown on glucose. YPG/AB showed the most efficient utilization of starch for ethanol production with the lowest levels of reducing sugars accumulating in the medium. The superior performance of YPG/AB as compared to YPB-G was found to correlate with its higher level of alpha-amylase activity. The ethanol production levels of YPG/AB in starch- and glucose-containing media were found to be comparable. YPB-G, which secretes the bifunctional fusion protein, could produce ethanol in media with starch concentrations above 100 g l(-1) while YPG/M(M) over dot did not produce ethanol from starch because of its negligible secretion of glucoamylase. (C) 1998 Elsevier Science Inc. [References: 13]