Combination of RNA sequencing and metabolite data to elucidate improved toxic compound tolerance and butanol fermentation of Clostridium acetobutylicum from wheat straw hydrolysate by supplying sodium sulfide

•Sodium sulfide (SS) can improve ABE fermentation from wheat straw hydrolysate.•Supplementation with SS affected the central fermentative metabolic pathway.•Supplementation with SS down-regulated metabolic flux toward acid formation branches.•Supplementation with SS up-regulated metabolic flux toward ABE formation branches.•Supplementation with SS demonstrated applied value for commercial ABE production.

Sodium sulfide (SS) was added to the non-detoxified wheat straw hydrolysate for ABE fermentation by Clostridium acetobutylicum CICC8012. Biochemical measurements demonstrated that supplementation with SS promoted earlier and enhanced conversion of acid to ABE and led to a 27.48% improvement in sugar consumption, a 20.48% improvement in the sugar-based ABE yield, a 47.63% improvement in the butanol titer, and a 53.50% improvement in the ABE concentration. The response of C. acetobutylicum CICC8012 at the mRNA level was examined by a transcriptional analysis performed with RNA sequencing. The expression of genes involved in the membrane transport of carbohydrates, glycolysis, and ABE formation increased following SS-supplemented fermentation, whereas the expression of genes encoding enzymes involved in acid formation decreased, which indicates that supplemental SS affected the central fermentative pathway, down-regulated the metabolic flux toward the acid formation branches, and up-regulated the metabolic flux toward the ABE formation branches.