Bioethanol production from starchy biomass by direct fermentation using Saccharomyces diastaticus in batch free and immobilized cell systems

Direct ethanol fermentation of soluble starch or dextrin with the amylolytic yeast Saccharomyces diastaticus was investigated in batch free and immobilized cells systems. In batch fermentations, the cells fermented high dextrin concentrations more efficiently. More than 92 g/l of ethanol was produced from 240 g/l of dextrin, at a conversion efficiency of 90%. The conversion efficiency decreased to 60% but a higher final ethanol concentration of 147 g/l was attained with a medium containing 500 g/l of dextrin. S. diastaticus in an immobilized cell bioreactor produced 83 g/l of ethanol from 240 g/l of dextrin, corresponding to an ethanol volumetric productivity of 9.1 g/l/h.