Influence of the Concentrations of D-Xylose and Yeast Extract on Ethanol Production by Pachyiolen tannophilus

To determine the most favorable conditions for the production of ethanol by Pachysolen tannophilus, this yeast was grown in batch cultures with various initial concentrations of two of the constituents of the culture medium: o-xylose (s,), ranging from 1 g-1-r to 200 g-l-‘, and yeast extract (I,), ranging from 0 g-1-r to 8 gel-‘. The most favorable conditions proved to be initial concentrations of s, = 25 g-Z_’ and 1, = 4 g-Z_‘, which gave a maximum specific growth rate of 0.26 h I, biomass productivity of 0.023 g. I-‘. h-r, overall biomass yield of 0.094 g.g-l, specific xylose-uptake rate (qs) of 0.3 g.g-r . h-r (for t=SO h), specific ethanol-production rate (qE) of 0.065 g.g-l. h-l and overall ethanol yield of 0.34 g-g-‘; qs values decreased after the exponential growth phase while qE remained practically constant.