Overexpression of GLT1 in fps1DeltagpdDelta mutant for optimum ethanol formation by Saccharomyces cerevisiae

Glycerol is the main byproduct produced under anaerobic ethanol fermentations by Saccharomyces cerevisiae and consumes a considerable amount of substrate. To verify the metabolic phenotype predications for increasing ethanol formation, two engineered S. cerevisiae KAM-14, KAM-15 strains were constructed for possible redirection of glycerol carbon flux into ethanol by overexpression of GLT1 in the fps1DeltagpdDelta mutant. The engineered strains KAM-14 and KAM-15 compared to the control strain KAM-2, produced 12.24% and 10.42% higher ethanol, 39.72% and 31.03% lower glycerol yield during anaerobic batch fermentations, respectively. The maximum specific growth rates of KAM-14 and KAM-15 were found to be relatively lower than that of KAM-2 during the exponential growth phase. In the meantime, the biomass concentrations of both KAM-14 and KAM-15 were similar to KAM-2. Acetate and pyruvate concentrations of KAM-14 and KAM-15 were greatly decreased comparing to those of KAM-2, respectively. These experimental results approved the metabolic pathway strategies to improve ethanol formation.