The batch experiment was performed with various glucose
concentrations to develop ethanol production. The initial
glucose concentrations in the batch experiments were 20, 40,
80, 160 and 300 kg m3 tested at 30 C. The experimental
conditions and the results summarized in Fig. 4 show the
changes in ethanol concentrations at different initial glucose
concentrations over a one week incubation period, while Fig. 5
demonstrates the specific ethanol production rate and
ethanol conversion rate at different initial glucose concentrations
after 48 and 72 hour’s incubation.
The production of ethanol was affected by the substrate
concentration between 20 and 300 kg m3
. As shown in Fig. 4,
higher substrate concentrations may achieve higher ethanol
production, but a longer incubation time was required for
higher initial glucose concentrations above 80 kg m3 at
a temperature of 30 C when the pH was not controlled. Moreover,
higher initial glucose concentrations, such as 300 kg m3
,
may have actually decreased the ethanol conversion efficiency
when the pH value was not controlled, since the higher
substrate and production concentrations may have inhibited
the process of ethanol fermentation (as