MIG1 Glucose Repression in Metabolic Processes of Saccharomyces cerevisiae: Genetics to Metabolic Engineering

Background: Although Saccharomyces cerevisiae has several industrial applications, there are still fundamental problems associated with sequential use of carbon sources. As such, glucose repression effect can direct metabolism of yeast to preferably anaerobic conditions. This leads to higher ethanol production and less efficient production of recombinant products. The general glucose repression system is constituted by MIG1, TUP1 and SSN6 factors. The role of MIG1 is known in glucose repression but the evaluation of effects on aerobic/anaerobic metabolism by deletion of MIG1 and constructing an optimal strain brand remains unclear and an objective to be explored. Methods: To find the impact of MIG1 in induction of glucose-repression, the Mig1 disruptant strain (DeltaMIG1) was produced for comparing with its congenic wild-type strain (2805). The analysis approached for changes in the rate of glucose consumption, biomass yield, cell protein contents, ethanol and intermediate metabolites production. The MIG1 disruptant strain exhibited 25 glucose utilization, 12 biomass growth rate and 22 protein content over the wild type. The shift to respiratory pathway has been demonstrated by 122.86 and 40 increase of glycerol and pyruvate production, respectively as oxidative metabolites, while the reduction of fermentative metabolites such as acetate 35.48 and ethanol 24. Results: Results suggest that DeltaMIG1 compared to the wild-type strain can significantly present less effects of glucose repression. Conclusion: The constructed strain has more efficient growth in aerobic cultivations and it can be a potential host for biotechnological recombinant yields and industrial interests

SACCHAROMYCES CEREVISIAE, KEY ROLE OF MIG1 GENE IN METABOLIC SWITCHING: PUTATIVE FERMENTATION/OXIDATION

Saccharomyces cerevisiae can utilize a wide range of carbon sources; however, in the presence of glucose the use of alternate carbon sources would be repressed. Several genes involved in the metabolic pathways exert these effects. Among them, the zinc finger protein, Mig1 (multicopy inhibitor of GAL gene expression) plays important roles in glucose repression of Saccharomyces cerevisiae. To investigate whether the alleviation of glucose effect would result in a switch to oxidative production pathway, MIG1 were disrupted in a haploid laboratory strain (2805) of S. cerevisiae. The impact of this disruption was studied under fully aerobic conditions when glucose was the sole carbon source. Our results showed that glucose repression was partly alleviated; i.e., ethanol, as a significant fermentation marker, and acetate productions were respectively decreased by 14.13 and 43.71 compared to the wild type. In Delta MIG1 strain, the metabolic shifting on the aerobic pathway and a significant increase in pyruvate and glycerol production suggested it as an optimally productive industrial yeast strain. However, further studies are needed to confirm these findings