Efficient biobutanol production by acetone-butanol-ethanol fermentation from spent coffee grounds with microwave assisted dilute sulfuric acid pretreatment

Abstract

The integral valorization of potential sugars (cellulosic and hemicellulosic) from spentcoffee grounds (SCG), a lignocellulosic residue, is proposed in this work. With this aim,the microwave assisted dilute sulfuric acid pretreatment has been optimized, leading toa hemicellulosic sugar recovery in the pretreatment liquid (HSR L ) and an enzymatichydrolysis yield of 79 and 98%, respectively, at 160.47 ºC and 1.5% H 2 SO 4 .Moreover, the complete digestibility of cellulose (enzymatic hydrolysis yield = 100%)was also discovered for non-pretreated SCG, which is very interesting. Secondly, theproduction of biobutanol, an advanced biofuel, is also proposed from pretreated SCGenzymatic hydrolysate and pretreatment liquid achieved under optimal conditions.These were fermented by Clostridium beijerinckii , yielding 95 kg butanol/t SCG (drymatter) and 151 kg acetone-butanol-ethanol/t SCG (dry matter).