Effects of alkaline hydrogen peroxide treatment on cellulose accessibility of switchgrass pretreated by acidic deep eutectic solvent

Abstract

Choline chloride: lactic acid (ChCl:LA) is a promising green acidic deep eutectic solvent for biomass fractionation and lignin extraction. This study reported an efficient ChCl:LA pretreatment for delignification and xylan solubilization from biomass. Under a mild condition (30 min, 130 °C), 83.4% lignin and 80.4% xylan were selectively removed from switchgrass. The pretreated switchgrass was highly enriched with cellulose (71.4%), but showed slow release of sugar. Its enzymatic hydrolysis efficiency was much improved by alkaline hydrogen peroxide (AHP) post-treatment. Synergistic effects of AHP suggested that additional physical barrier to cellulose accessibility could be created through side reactions between LA and cellulose. After AHP post-treatment, cellulose became highly accessible and digestible, with 94.1% glucose yield even at a high solid loading (20%). ChCl:LA can be recycled and reused without conditioning although pretreatment effectiveness diminished gradually. Overall, an efficient ChCl:LA pretreatment was developed for biomass pretreatment, and possible interaction between LA and cellulose during the pretreatment can be decoupled by AHP post-treatment.