Biobutanol production from brewer’s spent grain hydrolysates by Clostridium beijerinckii

•Brewer’s spent grain (BSG) as feedstock for ABE fermentation.•Acid dilute pretreatment at pH 1 recovered efficiently monosaccharides.•C. beijerinckii fermented enzymatic hydrolysates from pretreated BSG.•Pretreatment liquids can inhibit completely ABE fermentation.•Global yields of 75gbutanol/kg BSG and 95gABE/kg BSG. Brewer’s spent grain (BSG) is a promising feedstock for ABE fermentation. Sulfuric acid pretreatment of BSG at pH 1, 121°C and different solid loadings (5–15% w/w) was investigated. Enzymatic hydrolysis and ABE fermentation by Clostridium beijerinckii DSM 6422 of non-washed and washed pretreated BSG were performed to compare monosaccharide release and butanol production. Pretreatment at 15% w/w BSG resulted in higher availability of sugars in both the enzymatic hydrolysates and pretreatment liquid, and overall yields of 75gbutanol/kg BSG and 95gABE/kg BSG were obtained. When the enzymatic hydrolysate from the washed pretreated BSG was fermented, butanol (6.0±0.5g/L) and ABE (7.4±1.0g/L) concentrations were lower compared with 7.5±0.6g/L butanol and 10.0±0.8g/L ABE from a control. The fermentation of the liquid released in the pretreatment at 15% w/w resulted in a butanol production of 6.6±0.8g/L with a total ABE of 8.6±1.3g/L after overliming.