Yeast Mutant Produces Ethanol and Squalene from Crop Feedstock

GM yeast (Saccharomyces cerevisiae) capable of producing ethanol and other chemicals from agricultural feedstocks are of major interest to the biofuel industry. Swansea University's Diane E. Kelly, and her team, investigated the co-production of ethanol and squalene using S. cerevisiae strain YUG37-ERG1, where the squalene epoxidase (ERG1) is controlled by the doxycycline-repressible tet0 7 -CYC1 promoter. Ethanol and squalene production of YUG37-ERG1 grown using grass juice with doxycycline was assessed.

The tet0 7 -CYC1 promoter allowed the regulation of the expression of ERG1, which resulted in squalene accumulation. The strain fermented ethanol and accumulated the highest squalene content (7.89mg/g dry biomass) in grass juice with 5.) g/mL doxycycline and accumulated its highest yield (18.0mg/L squalene) from grass juice with 0.025 g/mL doxycycline.

This study is the first to utilize S. cerevisiae for the co-production of ethanol and squalene from grass juice. The findings demonstrate the potential to integrate microbial bioprocess engineering with existing agriculture.