Efficient ethanol production of an industrial strain of Saccharomyces cerevisiae with improved ethanol tolerance via evolutionary engineering

BACKGROUND AND OBJECTIVESIn order to optimize existing ethanol production, it is essential to maintain Saccharomyces cerevisiae growth and sugar metabolism during the fermentation process. Yeast viability and vitality in high-stress fermentation conditions are significant parameters in reaching the goal. Ethanol stress, as the main stress factor that causes a decrease in ethanol production in fermentation, causes many changes in S. cerevisiae, which include increased inhibition of metabolism, decreased growth and absorption of nutrients, and disruption of the membrane structure. It leads to an increase in membrane permeability and electrochemical loss. Ethanol tolerance is a complex phenotype that can be affected by diverse alleles that may show complex interactions and which may vary between different strains. Evolutionary engineering has considerable industrial consequences due to the toxicity that many bio-renewables have on microorganisms through production capacity and viability.MATERIALS AND METHODSIn the present study, to improve the ethanol tolerance phenotype in a strain isolated from the fermenter of an alcohol factory. The mother strain was mutated by physical and chemical methods. Mutants were screened using medium containing ۱-butanol. The original parent and the mutants were evolved over ۱۴۴ days by evolutionary engineering strategy, while the ethanol production of the selected strains was investigated. Ethanol production of selected strains was investigated in laboratory and industrial fermenters.RESULTS AND DISCUSSIONAccording to the increase in the maximum growth rate, ۹۶ strains were selected including parental strain and mutants, and the amounts of ethanol production of these strains were evaluated after evolutionary adaptation tests. Ethanol production of F۱۲۱, which was mutated with EMS before the adaptive evolution test and then evolved at ۹% v/v ethanol, was improved from ۹۶.۰±۰.۰۴ g/L to ۱۰۹.۳ ± ۱.۱ g/L.CONCLUSIONNowedays, evolutionary engineering is considered a powerful method in creating industrial strains with a desired phenotype. In this research, in order to increase ethanol tolerance in an industrial strain, evolutionary engineering strategy was used. To increase initial genetic diversity the population, before starting adaptive evolution experiments, mutagenesis was performed, and the results showed that mutagenesis accelerated the process of reaching the desired phenotype by increasing genetic diversity. The strain developed on an industrial scale was able to increase the yield and lead to an increase in efficiency.

کلیدواژه ها:

Saccharomyces cerevisiae ، ethanol production ، ethanol tolerance ، evolutionary engineering