The effect of inoculation rate of S.cerevisiae was investigated in
many reports [19]. The maximum bioethanol yield was obtained at
10% inoculation rate in the study conducted by Neelakandan and
Usharani [20]. In this mixed culture fermentation study, it was
found that low inoculation levels of S.cerevisiae led to effective
bioethanol production. The relation between the inoculation rates
of S.cerevisiae with respect to bioethanol production demonstrated
that bioethanol production was high at the low level of inoculation
rate of S.cerevisiae, when inoculation rates of A.sojae and T.harzianum
were low, agitation speed was high and vented flasks were
used (Fig. 1c). When inoculation rates of A.sojae and T.harzianum
were changed to high levels (other parameters were the same),
high bioethanol concentrations was obtained at low inoculation
levels of S.cerevisiae. Although aeration was a nonsignificant term
according to the model, its interactions were significant (Fig. 1d).
Therefore it could not be removed from the model due to the hierarchy
principle. The use of vented flasks led to higher bioethanol
concentrations than the sealed flask. Since microorganisms favoured
mild conditions and not strictly anaerobic conditions, this
was an expected result.