10 l of the culture medium and the ph was controlled within u00b1 0 05 ph units at various predetermined values by the automated addition of 1 n naoh the aeration rate was controlled at 0 75 l min and the stirring rate at 200 r p m for examples 14 and 15 and 100 r p m for examples 16 and 17 the fermentations of examples 14 and 15 were terminated after 146 hr and those of examples 16 and 17 after 138 hr the maximum rates of cell growth xylose consumption and ethanol production per unit of cells as well as the overall ethanol yield were determined as a function of ph the results are reported in table iii below table i______________________________________effect of temperature max xylose max etohex max cell consumption production etoham temp growth rate rate rate yieldple u00b0 c hr sup 1 g g u00b7 hr g g u00b7 hr g g sup a______________________________________2 15 0 09 0 12 0 05 0 263 20 0 14 0 26 0 06 0 274 25 0 16 0 32 0 07 0 275 28 0 19 0 44 0 11 0 286 32 0 24 0 49 0 12 0 347 40 0 06 0 0 0______________________________________ str1 table ii______________________________________effect of initial xylose concentration initial max xylose max etoh xylose initial cell consumption production etohexam conc growth rate rate rate yieldple g l hr.