Screening of strains of Saccharomyces cerevisiae for ethanol fermentation of very-high-gravity substrates

A strain usable for fermentation of highly concentrated substrates by very-high-gravity fermentation technology (VHG) was selected on the basis of fermentation activity of the strains at high initial substrate concentrations and in the presence of exogenously added ethanol. The capacity of 35 distillery, baker's and wine strains of yeasts Saccharomyces cerevisiae to ferment high glucose concentrations was studied in a medium without ethanol addition and with addition of 10% ethanol by volume. Three strains were selected on the basis of biomass increments, degree of glucose utilization and concentration of produced ethanol. Maximum concentration of produced ethanol and ethanol productivity expressed as the amount of produced ethanol in a given volume within a time interval were compared in media with increasing glucose concentrations (250, 300, 350 and 400 g/l). The highest ethanol concentration (74.4 g/l) and highest ethanol productivity (1.38 g/l/h) was recorded in strain Pz 90 at a glucose concentration of 400 g/l in medium. An increase in biomass concentration (up to 18 g/l) led to further increase in ethanol productivity (2.84 g/l).