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

Abstract

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 µmax 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.

Engineering and transcriptome study of Saccharomyces cerevisiae to produce ginsenoside compound K by glycerol

“…In the TCA cycle, NADH can be reduced by a metabolic flow from oxalate to malate, thus possibly increasing transcript levels to gain reducing power. [ 37 ] In the ethanol production pathway, transcript levels of alcohol dehydrogenase genes did not differ from those in glucose at both time points, except for ADH2 (Figure 4). Although the key isozymes of the pyruvate decarboxylase genes PDC1/2/3 were up‐regulated in glycerol, we did not detect ethanol production throughout the fermentation process.…”

“…The glycerol assimilating strain obtained by Nakanishi et al from S. cerevisiae also increased biomass after glycerol uptake. [37] The introduction of the glycerol metabolic pathway increased CK production by 43.0%, indicating that the use of glycerol as the sole carbon source was an effective method to increase CK production.…”

“…In the TCA cycle, NADH can be reduced by a metabolic flow from oxalate to malate, thus possibly increasing transcript levels to gain reducing power. [37] In the ethanol production pathway, transcript levels of alcohol dehydro- show the annotation results of differentially expressed genes enriched in the KEGG pathway, denoted as Glu24_versus_Gly24 and Glu60_versus_Gly60, respectively. p-value less than 0.05 is the criterion for significant enrichment.…”

“…Nakanishi et al found no ethanol production in YNBG under aerobic conditions in S. cerevisiae strain no.7, hypothesizing that intracellular redox reactions are difficult to control when glycerol is the sole carbon source. [37]…”

Evaluation of Cellular Responses by Chlamydomonas reinhardtii in Media Containing Dairy-Processing Residues Derived from Cheese as Nutrients by Analyzing Cell Growth Activity and Comprehensive Gene Transcription Levels

“…Given that the responses of microbial cells could be influenced by substrates as the nutrient stimuli [27], the comparative cellular responses of C. reinhardtii to WPC34 and WP should be evaluated through transcriptome analyses. A transcriptional analysis is favored to assess cellular responses toward environmental conditions earlier than proteomic and/or metabolomic analyses [28]. In this study, the investigation was performed on a green alga C. reinhardtii to reveal three aspects as follows: its ability to use the dairyprocessing residues as substrates; its trend to biosynthesize lipids as cell production using the dairy-processing residues; and its cellular response to adding the dairy-processing residues.…”