Fig. 5 shows the data for static and shaking conditions at 30 ◦C
for different time periods. As shown in Fig. 5, at 30 ◦C the concentration
of ethanol after 7 days reached up to the maximum level of
105 g/L in shaking conditions compared to the maximum produc-
Fig. 5. Ethanol production in shaking and static cultures at 30 ◦C using 50 mL of
WBFB supernatant contained in vials.
tion 91.5 g/L in static conditions. The CFU variation of yeast cells in
the supernatant of WBFB is much different from that in the original
WBFB shown in Table 1. The solid residue of WBFB seems to
affect the populations of microbial cell consortium. CFU of yeast
cells for the static culture at 30 ◦C increased from initial 7.0 CFU/mL
to 4.0
×
102 after 5 days and 2.0
×
105 after 7 days. The variation in
the population of live yeast cells for shaking culture was nearly the
same with that for static culture. A slight increase in ethanol production
in shaking conditions is reasonable because the contact of
yeast cells with the nutrients was more effective in shaking compared
to static conditions. This can be supported by the fact that
biochemical reactions during fermentation are greatly affected by
the mixing and mass transfer of substrates to microorganism [33].