Investigation of morphophysiological properties of yeast promising for ethanol production

Ethyl alcohol is widely used in the food, medical, and cosmetic industries, and is also considered an alternative to traditional fuels due to its renewability and environmental safety. In the context of the global growth of interest in biofuels, research aimed at selecting yeast strains with high productivity and resistance to ethanol is of particular importance. The purpose of this work was to study the morphophysiological characteristics and alcohol resistance of Saccharomyces cerevisiae strains used in biotechnological processes. The objects of the study were strains C16, C25 and C48 from the collection of ITMO University, as well as the control strain of baker's yeast RCAM 02150. The molecular genetic identification was carried out by PCR and HRM analysis. Physiological activity was assessed by the volume of carbon dioxide released and the content of dead cells after cultivation in an ethanol medium. Additionally, the morphology and flocculation ability of yeast were studied. The results showed that yeast strain C25 is characterized by the highest enzymatic activity while maintaining high viability in the presence of 10-20% ethanol. Strain C16 showed lower metabolic activity, which is probably due to increased flocculation. At the same time, all strains have a close taxonomic relationship and differ in cell shape and size. The revealed differences emphasize the need to use comprehensive approaches in yeast screening, including morphological analysis, cell quantification, and determination of physiological resistance to ethanol stress.