Pretreatment with fermentable and recyclable deep eutectic solvent (DES) for improving resource utilization of biomass

Abstract

A series of acidic FDES were prepared to pretreat lignocellulose. After pretreatment, solid product containing 82% cellulose, high quality lignin and liquid product containing hemicellulose were obtained, respectively. The enzymatic hydrolysis of the solid product could reach 84.5%. The enzymatic hydrolysate with the was used as feedstock for ethanol fermentation using commercial Saccharomyces cerevisiae live preparation instead of genetically engineered strains that can use 5-carbon sugars. The pretreatment solution was used as a raw material to culture Rhodotorula glutinis for microbial lipid production. phosphoric acid (PA) as a pretreatment catalyst could ensure the enzymatic efficiency compared with other acids, while more polysaccharide fractions could be formed. At the end of fermentation, the biomass could reach 30 g/L, and the lipid concentration could reach 7 g/L. In addition, the lignin prepared in this study has a consistent structure and low molecular weight, showing high potential for bio-based chemicals and materials conversion. According to the results of FDES reutilization, the pretreatment effect and fermentation effect of the FDES prepared here did not decrease significantly with the increase in the reutilization. The biomass pretreatment process developed in this study realized the full utilization of cellulose, hemicellulose, lignin and pretreatment solvent. It is innovative compared with the genetically engineered strain which mainly rely on the co-fermentation of glucose and xylose for cellulosic ethanol fermentation.