Effect of pH
The rate of ethanol production from wood
hydrolyzates was not significantly affected by pH in the
range of 5.1±7.0 (data not shown, P> 0.05). Ethanol
production was maximum at pH 6.0. The fermentation
of mixed sugars in this batch of hydrolyzate (batch VI)
was completed rapidly (in less than 48 h) because of the
low acetate content. Acid hydrolyzate batch VIII, which
had a pH of 7.7, produced 30% less ethanol by fermentation
and hence suffered lower yields. For acid
hydrolyzate batches with a pH of less than 4, growth
and fermentation did not occur unless the pH was readjusted
to pH 5.5±6.