Optimizing deep eutectic solvent pretreatment for enhanced glucan recovery from miscanthus

Abstract

This work focuses on the use of the deep eutectic solvent composed of choline chloride and acetic acid (1 : 2) in the pretreatment of the perennial energy crop Miscanthus, commonly called silvergrass. The pretreatment time and temperature were optimized to achieve a maximum of the glucan and minimum of the lignin contents in the pretreated biomass. In the optimization approach, the maximal glucan recovery in the pretreated solid was also considered. The performed optimization resulted in conditions (2 h 52 min and 150 °C), at which a pretreated biomass contained 74.1 wt% and 9.5 wt% of glucan and lignin respectively, and a glucan recovery was as high as 87.0 wt%. Furthermore, the biocompatibility of deep eutectic solvent was evaluated by using enzymatic hydrolysis washed and unwashed pretreated biomass produced at optimal conditions. The enzymatic hydrolysis of washed biomass resulted in higher glucan and xylan conversion than those achieved from unwashed biomass, deeming the step of biomass washing necessary. This was confirmed by the fractal kinetics modelling that confirmed higher accessibility of glucan for washed biomass than for unwashed Miscanthus sample.