(29v) Metabolic Engineering of Thermoanaerobacterium Aotearoense SCUT27 for Biofuels Production from Sucrose and Molasses

Thermoanaerobacterium aotearoense strain SCUT27 has been considered as an efficient ethanol producer at 55^oC with broad substrate spectrum, but it lacks the key enzymes for sucrose metabolism. Herein, the sucrose-6-phosphate hydrolase (scrB) from a new screened strain Thermoanaerobacterium thermosaccharolyticum G3-1 was overexpressed in SCUT27, endowing it with the ability to utilize sucrose. Additionally, expression of the sucrose-specific PTS system (scrA) from Clostridium acetobutylicum and knockout of the redox-sensing transcriptional repressor (rex) in strain SCUT27 further strengthened the biofuels production from sucrose. With the gene arginine repressor (argR) deleted, the ethanologenic mutant P8S10 showed great inhibitors-tolerance and accumulated ~34 g/L ethanol (with a yield of 0.49 g/g sugar) using pretreated cane molasses in 5 L tank by fed-batch fermentation. When overexpressing the butanol metabolic pathway in strain P8S07, an alcohol yield of 0.33 g/g sucrose was obtained with the butanol/total solvent ratio of 0.23 (w/w). This study demonstrated the potential application of the engineered strains of SCUT27 for economic biofuels production from low cost cane molasses.