Sequencing of Clostridium acetobutylicum DSM 792 mutants with inactivated transcriptional repressors araR and/or xylR

The solventogenic bacterium Clostridium acetobutylicum is naturally able to produce chemicals of interest by fermentation, such as acetone, butanol and ethanol. Currently, carbon catabolite repression (CCR) mechanisms found in this micro-organism impede the efficient assimilation of pentoses in the presence of hexoses. Since both types of sugars are commonly found in lignocellulose hydrolysates, those mechanisms lead to poor carbohydrate utilization when fermenting these substrates. The aim of this study was to tackle CCR mechanisms in C. acetobutylicum by genetic engineering, to obtain a micro-organism able to assimilate simultaneously hexoses and pentoses, which could therefore be utilized to efficiently produce chemicals of interest from 2G substrates. A CRISPR-Cas9 genetic tool was employed to delete the genes encoding several putative transcriptional repressors involved in the assimilation pathway of pentoses. Mutants were characterized by analyzing the kinetics of carbohydrate assimilation when grown on media containing sugar mixtures. The effect of genes deletion was precisely assessed by transcriptomic analyses.