2.3. Culture conditions
The immobilized or free cells of S. cerevisiae were cultured in
YPD broth with the addition of 10%
glucose at pH 5.0, 30 C,
and 150 rpm. Ethanol was added initially to the broth ranging from
0 to 10%). For ethanol fermentation, the co-immobilization
gel beads (2 or 3 strains of microorganisms) were incubated at
pH 4.0, 30 C, and 150 rpm. To achieve limited aerobic conditions,
flasks were fitted with a one-hole silicon stopper into which
a cotton-plugged Pasteur pipette was inserted to vent out CO2
during fermentation