3.3. Simultaneous saccharification and ethanol fermentation of L.
japonica hydrolysates
Ethanol yields for acid lysates treated with enzymes and
simultaneously inoculated with E. coli KO11 or S. cerevisiae or sequentially with S. cerevisiae and E. coli KO11 are illustrated in
Fig. 5. Fermentation with S. cerevisiae alone resulted in ethanol
concentrations of 7.0–9.8 g/L. This low yield was likely due to the
yeast’s inability to utilize mannitol. Removal of the yeast from
the fermentation medium and inoculation of this medium with
E. coli KO11 resulted in a final ethanol yield of 23–29 g/L, since
the E. coli was able to utilize the mannitol that had remained in
the medium. A similar yield was obtained when E. coli KO11 was
added to the acid hydrolysate along with the enzymes. The lower
concentration of ethanol in acid- and Viscozyme L-treated hydrolysate
can be attributed to the lower content of consumable sugars
as shown in Table 3.