Improving the productivity of bioethanol production using marine yeast and seawater-based media

Abstract

Water consumption has become a serious concern in renewable fuel production as demand for biofuels increases to address environmental issues associated with the use of fossil fuels. In recent years, several research groups have suggested seawater (SW) as a promising alternative to fresh water (FW) for the production of biofuels. However, the use of seawater rather than fresh water in the fermentation process is still a relatively unexplored area of research. In this paper, the tolerance of the marine yeast S. cerevisiae AZ65 to the presence of salts in seawater was investigated. The results indicated that S. cerevisiae AZ65 grew well in media containing up to 10.5% (w/v) sea salts and 20% (w/v) glucose compared with an industrial distiller's strain, S. cerevisiae NCYC2592. A multi-stage batch fermentation process was also investigated to increase ethanol productivity. Two different seawater based media were used: SW-YPD medium and SW-molasses medium. S. cerevisiae AZ65 achieved an ethanol concentration of 113.52 gL-1 with a productivity of 4.15 g L−1h−1 using SW-YPD medium and an ethanol concentration of 50.32 gL-1 with a productivity of 2.46 g L−1h−1 using SW-molasses medium. These results confirmed the potential of seawater and marine yeasts for implementation in the bioethanol industry using a multi-stage fermentation process.