Influence of the concentrations of d-xylose and yeast extract on ethanol production by Pachysolen 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: d-xylose (s_o), ranging from 1 g·l^?1 to 200 g·l^?1, and yeast extract (l_o), ranging from 0 g·l^?1 to 8 g·l^?1. The most favorable conditions proved to be initial concentrations of S_o=25 g·l^?1 and l_o=4 g·l^?1, which gave a maximum specific growth rate of 0.26 h^?1, biomass productivity of 0.023 g·l^?1·h^?1, overall biomass yield of 0.094 g·g^?1, specific xylose-uptake rate (q_s) of 0.3 g·g^?1·h^?1 (for t=50 h), specific ethanol-production rate (q_E) of 0.065 g·g^?1·h^?1 and overall ethanol yield of 0.34 g·g^?1; q_s values decreased after the exponential growth phase while q_E remained practically constant.