Estimation of Carbon Metabolism in Saccharomyces cerevisiae Acclimatized to Glycerol Assimilation with Quantitative PCR

Saccharomyces cerevisiae has the potential to produce value-added chemicals; however, this strain is restricted by using glycerol as a carbon source. Although acclimatization of S. cerevisiae as a glycerol-assimilating strain was confirmed so far, the reason why S. cerevisiae can be acclimatized was not clear in detail with limited information on the metabolic changes. In this report, glycerol-assimilating strains from S. cerevisiae BY4741 were isolated, and the biomass production, ethanol fermentation, and transcription levels related to glycolysis and the tricarboxylic acid cycle under aerobic and slightly anaerobic conditions were analyzed. As the results show, although mu max was equal to 0.15 h(-1) between wildtype and glycerol-assimilating strains in an aerobic culture including glucose, the differences in max biomass production and percentage yields of ethanol and transcription levels between the two strains were shown. In slightly anaerobic culture, the differences in transcription levels downstream of glycolysis were also displayed. In the case of the glycerol-assimilating strain with glycerol under aerobic conditions, although the transcription levels related to ethanol production were sufficient, the ethanol production was not detected. Additionally, the biomass production reached a plateau even in the culture containing sufficient glycerol, indicating that the redox imbalance even in the cells of the glycerol-acclimatized strain could disturb the utilization of glycerol. The obtained knowledge will promote the use of glycerol resources with the glycerol-acclimatized S. cerevisiae in view of carbon recycling.

Automated summary

In this study, glycerol-assimilating strains were isolated from S. cerevisiae BY4741, and the changes in biomass production, ethanol fermentation, and transcription levels related to glycolysis and the tricarboxylic acid cycle under aerobic and slightly anaerobic conditions were analyzed. The results showed differences in biomass production, ethanol yields, and transcription levels between wildtype and glycerol-assimilating strains under aerobic conditions. Differences in transcription levels downstream of glycolysis were also observed under slightly anaerobic conditions. The study suggests that redox imbalance in glycerol-acclimatized strains may hinder glycerol utilization.