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

The integral valorization of potential sugars (cellulosic and hemicellulosic) from spent coffee grounds (SCG), a lignocellulosic residue, is proposed in this work. With aim, the microwave assisted dilute sulfuric acid pretreatment has been optimized, leading to hemicellulosic sugar recovery liquid (HSRL) an enzymatic hydrolysis yield 79 98%, respectively, at 160.47 °C 1.5% H2SO4. Moreover, complete digestibility cellulose (enzymatic = 100%) was also discovered for non-pretreated SCG, which very interesting. Secondly, production biobutanol, advanced biofuel, pretreated SCG hydrolysate achieved under optimal conditions. These were fermented by Clostridium beijerinckii, yielding 95 kg butanol/t (dry matter) 151 acetone-butanol-ethanol/t matter).