Rapid and efficient microwave-assisted guanidine hydrochloride deep eutectic solvent pretreatment for biological conversion of castor stalk

Microwave-assisted guanidine hydrochloride deep eutectic solvents (DESs) was developed for rapid and efficient pretreatment of castor stalk. The DES synthesized with guanidine hydrochloride and lactic acid showed a better delignification (92.02%) and enzymatic saccharification yield (96.3%) than choline chloride and lactic acid DES resulted. In addition, high-purity (up to 98%) lignin was recovered from the pretreatment liquor. The good recyclability of the guanidine hydrochloride-based DES was also proven with up to 90% cellulose hydrolysis with third-time recycled DES without post purification. The proposed microwave-assisted guanidine hydrochloride/lactic acid DES showed its great potentials as a highly effective and recyclable pretreatment solvent for future biorefinery strategies.