Wen-Shiang et al (2012) [40] investigated the
bioethanol production from sweet potato, the
saccharification and fermentation conditions of co-
immobilization of saccharolytic molds (Aspergillus
oryzae and Monascus purpureus) with
Saccharomyces cerevisiae. The immobilized yeast
cells showed that at 10% glucose YPD (yeast
extract peptone dextrose) the maximum
fermentation rate was 80.23%. Viability of yeasts
cells were 95.70% at a final ethanol concentration
of 6%. Immobilization enhanced the ethanol
tolerance of yeast cells. In co-immobilization of S.
cerevisiae with A. oryzae or M. purpureus, the
optimal hardening time of gel beads was between
15 and 60 min. Bioethanol production was 3.05-
3.17% (v v-1) and the YE/s (yield of ethanol
production/starch consumption) was 0.31-0.37 at
pH 4, 30°C and 150 rpm during 13 days
fermentation period. Co-immobilization of S.cerevisiae with a mixed cultures of A. oryzae and
M. purpureus at a ratio of 2:1, the bioethanol
production was 3.84% (v v-1), and the YE/s was
0.39 for 11 days incubation. However a ratio of A.
oryzae and M. purpureus at 1:2 resulted a
bioethanol production rate of 4.08% (v v-1), and a
YE/s of 0.41 after 9 days of fermentation.