Development of high temperature simultaneous saccharification and fermentation by thermosensitive Saccharomyces cerevisiae and Bacillus amyloliquefaciens

Scarcity of energy and pollution are two major challenges that have become a threat to all living things worldwide. Bioethanol is a renewable, ecological-friendly clean energy that may be utilized to address these issues. This study aimed to develop simultaneous saccharification and fermentation (SSF) process through high temperature-substrate adaptation and co-cultivation of S. cerevisiae with other potential amylolytic strains. In this study, we adapted our previously screened thermosensitive Saccharomyces cerevisiae Dj-3 strain up-to 42 °C and also screened three potential thermotolerant amylolytic strains based on their starch utilization capability. We performed SSF fermentation at high temperature by adapted Dj-3 and amylolytic strains using 10.0% starch feedstock. Interestingly, we observed significant ethanol concentration [3.86% (v/v)] from high temperature simultaneous saccharification and fermentation (HSSF) of adapted Bacillus amyloliquefaciens (C-7) and Dj-3. We attribute the significant ethanol concentration from starch of this HSSF process to C-7’s high levels of glucoamylase activity (4.01 U/ml/min) after adaptation in starch (up-to 42 °C) as well as Dj-3's strong glucose fermentation capacity and also their ethanol stress tolerance capability. This study suggests the significant feasibility of our HSSF process.