Increasing ethanol resistance in Saccharomyces cerevisiaeusing Adaptive laboratory evolution

Background and Aim : Adaptive laboratory evolution (ALE) is one of the most powerful methodsfor improving industrial strains. Its main applications are the activation of latent metabolicpathways, the ability to use unusual raw materials, the production of unusual products, and theincrease of yield and productivity of the production process. Ethanol is the most widely usedproduct in the world produced by biotechnological processes. It is also an important alternativeenergy source to fossil fuels. Ethanol is used as an industrial solvent in the pharmaceutical andperfume industries. Members of the Saccharomyces genus have been used for industrial ethanolproduction. Increasing the tolerance of ethanol-producing strains is one of the most importantcharacteristics of industrial strains. The strains of S. cerevisiae used in alcohol-producing factoriesin Iran differ significantly in their ethanol tolerance from industrial strains in the world. The aimof this study was to find the most resistant yeast strains in Iran and increase their ethanol toleranceby ALE.Methods : For this purpose, ۱۱ different strains of alcohol producing yeasts were prepared fromdifferent domestic and foreign sources. These strains were screened to find the strain with thehighest ethanol resistance. The selected strain was cultured in a medium containing edible sugaras the main carbon source, yeast extract as the main nitrogen source, and ۶.۵% ethanol. Coloniestolerating ۶.۵% ethanol were selected and cultured in the same medium with a higher ethanolconcentration (۰.۱%). By repeating the above steps, a strain tolerant to ۸% ethanol was obtained.The kinetics of the ethanol production process in the adapted and the initial strains were determinedby measuring the yeast growth rate, ethanol production rate, and substrate consumption rate.Results : The results showed that the biomass production of the adapted strain increased by ~۶.۸%compared to the parent strain. However, the alcohol production rate of the adapted strain was ۲.۹times that of the parent strain, and the specific growth rate of the parent strain was ۰.۰۰۲۴, whileit increased to ۰.۰۳۰ in the adapted strain.Conclusion : The result of this study shows the efficiency of ALE method to produce alcoholproducing industrial strains.

کلیدواژه ها:

Ethanol ، Adaptive laboratory evolution ، Saccharomyces cerevisiae ، ethanolresistance.