Abstract
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.
Highlights
Scarcity of energy and pollution are two major challenges that have become a threat to all living things worldwide
Conventional multistage use of commercial amylase enzymes for liquefaction and saccharification followed by fermentation in separate hydrolysis and fermentation (SHF) process have two main drawbacks: (a) process is carried out in two separate independent reactors for saccharification and fermentation as a result the capital cost is relatively higher than the simultaneous process; (b) the detoxifying effect of fermented inhibitors present in the pretreatment hydrolysate, which decreases the overall performances of the process
Simultaneous saccharification and fermentation (SSF), in which enzymatic hydrolysis is coupled with fermentation by yeast in the same vessel is advantageous over SHF process because it requires less equipment and fermentation time[10]
Summary
Scarcity of energy and pollution are two major challenges that have become a threat to all living things worldwide. 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. We performed SSF fermentation at high temperature by adapted Dj-3 and amylolytic strains using 10.0% starch feedstock. Detection of suitable couple co-cultivating thermotolerant amylolytic and fermenting strain offers an advantage for performing hydrolysis and fermentation at elevated temperature. This will contribute in the improvement of SSF fermentation efficiency along with reduction of cooling costs and helps in preventing contamination[18–22]. Our results suggest the feasibility of high temperature starch-based bioethanol production using thermotolerant S. cerevisiae and Bacillus amyloliquefaciens
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