Pretreatment of multiple lignocellulosic batches with recoverable and fermentable deep eutectic solvent (FDES) for co-production of sugar, lignin and lipid

Addressing the high cost of comprehensive utilization of lignocellulose, an efficient and green lignocellulosic biorefinery process was developed in this study, which can achieve the co-production of lignin, sugar and lipid. A series of FDES were prepared using glycerin, choline chloride (ChCl), and H2SO4 for the pretreatment of lignocellulose and ultimately for fermentation. After optimization, the hemicellulose removal reaches 98%, and enzymatic hydrolysis rate of pretreated solids exceeds 90%. The FDES was then recovered and reused for pretreatment, in total five batches of lignocellulose were pretreated, only a slight decrease in lignin and hemicellulose removal rate occurred, no significant decrease in lignin yield, and a decrease in solid enzyme hydrolysis from 83.26% to 78.25%. Finally, FDES after using five batches was used as a substrate for Rhodotorula glutinis with biomass up to 40.25 g/L and lipid concentration up to 8.33 g/L. In addition, the cellulose was probed with high solid-loading enzymatic hydrolysis, obtaining high concentration of glucose (137.4 g/L) for ethanol fermentation. In conclusion, this study developed a biorefinery technology for the efficient utilization of lignocellulosic fractions and pretreatment solvents, which reduces the cost of DES pretreatments of lignocellulose, and achieves the cogeneration of lignin, sugar and lipids.