Increase of ethanol productivity by cell-recycle fermentation of flocculating yeast

Using the recombinant flocculating Angel yeast F6, long-term repeated batch fermentation for ethanol production was performed and a high volumetric productivity resulted from half cells not washed and the optimum opportunity of residual glucose 20 g l⁻¹ of last medium. The obtained highest productivity was 2.07 g l⁻¹ h⁻¹, which was improved by 75.4% compared with that of 1.18 g l⁻¹ h⁻¹ in the first batch fermentation. The ethanol concentration reached 8.4% corresponding to the yield of 0.46 g g⁻¹. These results will contribute greatly to the industrial production of fuel ethanol using the commercial method with the flocculating yeast.