OPTIMUM PH AND TEMPERATURE CONDITIONS FOR XYLOSE FERMENTATION BY PICHIA-STIPITIS

Pichia stipitis NRRL Y‐7124 is a xylose‐fermenting yeast able to accumulate ca. 57 g/L ethanol. Because optimum process conditions are important, data were collected to determine the effects of temperature and pH on growth and fermentation rates and product accumulations. Temperatures (26–35°C) providing optimum biomass and ethanol productivities did not necessarily provide maximum ethanol accumulation. Xylitol and residual xylose concentrations increased with temperature. Maximum ethanol selectivity was achieved at 25–26°C with minimal sacrifice to production rates. The temperature optimum for xylose could not be generalized to glucose fermentations, in which ethanol productivity and accumulation were optimum at 34°C. The optimum pH range for growth and fermentation on xylose was 4–7 at 25°C. Copyright © 1990 John Wiley & Sons, Inc.