Phenotypic Characterization of Non-Conventional Yeast Strains for Biofuel Production

Abstract

Biofuels such as bioethanol provide alternatives to conventional fossil fuels that are not only much less harmful to the environment, but also more readily utilized because they can be blended with gasoline to run cars without requiring an upheaval in current transportation fuel infrastructure. In first generation bioethanol production using the conventional yeast Saccharomyces cerevisiae, sugars of food crops such as corn and sugarcane are converted in industrial scale fermentations. However, this process not only competes with the agricultural industry in food-versus-fuel debates, but also requires significant amounts of freshwater. Second generation biofuel production with lignocellulosic biomass also poses difficulties in the type of carbon sources available and harsh conditions required for fermentation. Many non-conventional yeasts that may have potential for biofuel production, especially third generation biofuels using algae as biomass and seawater instead of freshwater, remain rarely explored. In this research, a selection of non-conventional yeasts was characterized for their ability to ferment different sugars in high salt environments. Many of the yeasts exhibited better growth and halotolerance than S. cerevisiae in media with salt concentrations comparable to that of seawater and higher. Additionally, select yeasts appeared to grow better in media with combined glucose and alginate, although they cannot grow with alginate as its sole carbon source. Based on growth assays and kinetics characterizations, a list of yeasts are recommended for further phenotypic and genetic study.