Efficient use of brewer's spent grain hydrolysates in <scp>ABE</scp> fermentation by <i>Clostridium beijerinkii</i>. Effect of high solid loads in the enzymatic hydrolysis

Abstract

Abstract BACKGROUND Brewer's spent grain (BSG) has been employed to investigate the use of hemicellulosic and cellulosic sugars in Acetone‐Butanol‐Ethanol (ABE) fermentation. A dilute‐acid pretreatment was conducted, followed by enzymatic hydrolysis at different solid loads (10–15–20% DM) and ABE fermentation by Clostridium beijerinckii DSM 6422. Operation at solid loadings higher than 15% DM (60.1 g L −1 of total sugars, 1.03 g phenolic/L) makes the development of a detoxification step necessary. RESULTS The higher butanol and ABE concentrations for the pretreatment liquor were obtained when activated carbon was used as the detoxification agent (11.5 ± 0.1 g L −1 butanol, 16.2 ± 0.2 g L −1 ABE, 95.1% sugar uptake), whereas the sequential activated carbon and overliming detoxification strategy was the most effective for 15% DM enzymatic hydrolysates (11.6 ± 0.2 g L −1 butanol, 18.3 ± 0.3 g L −1 ABE, 89.6% sugar uptake). CONCLUSION The overall yield, taking into account the pretreatment liquor and enzymatic hydrolysate, was 99.8 g butanol/kg BSG and 146.5 g ABE/kg BSG, improving the results without detoxification by more than 40%. © 2020 Society of Chemical Industry