Bioethanol production potential of a novel thermophilic isolate Thermoanaerobacter sp. DBT-IOC-X2 isolated from Chumathang hot spring

Dilute acid pretreatment of biomass generates enormous amount of hydrolysate (rich in inhibitors and pentose sugars), that remains unutilized for bioethanol production due to inadequacy of efficient C5-fermenting organisms. In this study, a predominantly pentose fermenting extremely thermophilic bacterium strain DBT-IOC-X2, pertaining to the genus Thermoanaerobacter was isolated from Himalayan hot spring. Batch experiments indicated substantial inhibitor resistance (2 g dm−3for furfural, 5-HMF, and acetic acid), substrate tolerance (∼15 g dm−3), co-sugar fermentation ability (co-production ethanol yield of 0.29 g/g), and high ethanol yield (83.57% and 91.12% of the theoretical maximum from 5 g dm−3glucose and xylose, respectively) by the bacterium at 70 °C and pH 8.0. Here, bioethanol production process was developed using pre-treated rice straw hydrolysate (PRSH) as low-cost agro-waste and 83.47% of the total sugar conversion was obtained. This study shows that Thermoanaerobacter sp. DBT-IOC-X2 could utilize diluted PRSH efficiently to improve the overall cost-effectiveness of biomass processing to bioethanol.