Improved Ethanol Formation By Constructing The Saccharomyces Cerevisiae Strain Based On Metabolic Engineering Principles

In this investigation we brought forward the metabolic pathway modification strategies to construct engineering strains of the Saccharomyces cerevisiae based on the computational predication results of elementary flux mode analysis. In this work, fps1Δ, gpdΔand overexpression of GLT1 mutant strains were constructed based on the control industrial strain KAM-2(MATαura3),as a consequence by mating, sporulating and dissecting genetically modified haploid strains, two improved engineered strains KAM-14(MATa ura3 fps1Δ::REPEAT gpd1Δ::REPEAT PpGK1-GLT1) and KAM-15(MATa ura3 fps1Δ::REPEAT gpd2Δ::REPEAT PpGK1-GLT1) were constructed.Anaerobic batch fermentation experiments were carried out with KAM-14, KAM-15 and KAM-2, meanwhile their absorbance of the culture, consumption of glucose, production of glycerol, ethanol, acetate and pyruvate were monitored in time courses of the experiments. The experimental results showed that the OD and consumption of glucose in KAM-14 and KAM-15 were similar to KAM-2. Meanwhile, compared to KAM-2, there were 39.21% and 37.02% reduction in glycerol formation, ethanol production increased by 12.65% and 11.64% for KAM-14 and KAM-15, and dramatic reduction in the formations of acetate and pyruvate, respectively.According to metabolic flux model of Saccharomyces cerevisiae, the metabolic flux distributions of KAM-14, KAM-15 and KAM-2 under anaerobic fermentation conditions were calculated, respectively. The both increased ethanol metabolic flux of engineered strains had shown that they have better fermentation ability and the metabolic pathway modification strategies were rational.Sym1Δand overexpression of gene SYM1 mutant strains were constructed based on the corresponding engineered strains and laboratorial strains, respectively. The experimental results indicated that overexpression of SYM1 engineered strain has not brought about obviously improved growth phenotypes.