(27bd) Harnessing Robustness of Thermophilic Bacillus Coagulans for Conversion of Switchgrass Hydrolysates to Designer Bioesters at Elevated Temperatures

Bacillus coagulans is a gram-positive thermophilic bacterium that can grow at elevated temperatures, utilize biomass hydrolysates, and produce lactate at high levels. We aim to understand and harness its robustness for conversion of biomass hydrolysates to designer bioesters (e.g., acetate esters, lactate esters) that have broad use as solvents, flavors, fragrances, and advanced biofuels. Through comprehensive screening of diverse undomesticated B. coagulans strains isolated from different environmental niches against a wide range of temperatures (30-60^oC), either single or mixed C5/C6/C12 sugars, and lactate concentrations (0-60 g/L), we found that most of the strains could grow in all the environments tested with different degrees of robustness. Some candidates could utilize all sugars with minimal exhibition of diauxic growth, grow optimally at 55^oC, and tolerate high concentrations of lactate up to at least 40 g/L, which serve as reference strains for elucidating cellular robustness and metabolic engineering. To investigate underlying genotypes, genome re-sequencing was performed on representative strain B-768, revealing it has the largest B. coagulans genome sequenced to date and accordingly, an expanded carbon metabolism and mobilome. Proteomic analysis showed B-768 is capable of metabolizing sugars in biomass hydrolysates and producing lactate. Overall, B. coagulans is a promising microbial manufacturing platform that will be advanced by a fundamental understanding of its robustness and the ability to harness it for production of designer bioesters from lignocellulosic hydrolysates.