Integrated Hydrolysis-fermentation of Sweet Potato for Bioethanol via Co-culture of Saccharomyces cerevisiae TISTR 5088 and Saccharolytic Mold Isolates

This study evaluated bioethanol production from sweet potato flour using simultaneous saccharification and fermentation (SSF) and separate hydrolysis and fermentation (SHF) with commercial enzymes and mixed microbial cultures. Under SSF, the commercial enzyme control produced 14.90 ± 0.61 g/L ethanol at 96 h, while the co-culture of Saccharomyces cerevisiae TISTR 5088 and Amylomyces rouxii TISTR 3182 achieved a comparable ethanol concentration of 14.35 ± 0.18 g/L at only 60 h. The mixed fungal culture also produced similar ethanol levels, whereas the A. oryzae-based system showed lower performance. Although SHF promoted glucose accumulation during hydrolysis, ethanol production required a longer fermentation time, with the highest SHF ethanol concentration of 15.04 ± 0.35 g/L obtained from the mixed fungal system at 108 h. Overall, SSF using S. cerevisiae TISTR 5088 and A. rouxii TISTR 3182 was identified as the most suitable strategy due to its shorter processing time, simpler operation, and comparable ethanol yield to commercial enzymes. These findings demonstrate the potential of A. rouxii TISTR 3182 as an alternative amylolytic microorganism for reducing enzyme dependency in starch-based bioethanol production.