Engineering Thermotolerant Biocatalysts for Biomass Conversion to Products

Abstract

The main objective of this study is to identify thermotolerant facultative anaerobic bacteria that can ferment all the sugars that can be derived from lignocellulosic biomass to ethanol at 50°C and pH 5.0 that has been reported to be near optimal for the activity of commercial fungal cellulases being developed for simultaneous saccharification and fermentation of cellulose to ethanol. Since such a bacterium has not been described in the literature, we have embarked on isolating a bacterium from nature that can be engineered to ferment the biomass-derived sugars to ethanol. From about 77 environmental samples we have isolated bacteria that can grow both aerobically and anaerobically at 50°C and pH 5.0 in media containing xylose as the primary carbon source. From a total of 380 bacterial isolates we have identified strains 17C5, 36D1 and P4-102B for further study based on their growth and fermentation characteristics. Based on 16S rRNA(DNA) sequence the three bacterial isolates (strains 17C5, 36D1 and P4-102B) were identified as Bacillus coagulans that forms a diverse group of sporogenic lactic acid bacteria.