Facile fractionation of poplar by a novel ternary deep eutectic solvent (DES) for cellulosic ethanol production under mild pretreatment conditions

Abstract

The efficient fractionation of lignocellulosic biomass using deep eutectic solvent (DES) is emerging as an innovative and eco-friendly approach. In this study, a novel ternary DES composed of triethylbenzyl ammonium chloride (TEBAC), p-toluene sulfonic acid (TsOH), and ethylene glycol (EG) was employed for the pretreatment of poplar wood to enhance cellulosic ethanol production. Key pretreatment parameters, including temperature, DES molar ratios, and reaction time, were systematically optimized. Under optimal conditions (90 ºC, 60 min, TEBAC/TsOH/EG ratio of 1:1.5:3) lignin removal reached 90.64±1.28 % and xylan removal achieved 85.56±1.34 %, significantly improving cellulose digestibility. The improvement might be attributed to the removal of hemicellulose and lignin, which exposed cellulose and enhanced the accessibility of cellulase to cellulose. Additionally, optimized enzymatic hydrolysis yielded a glucose concentration of 65.98±0.97 g/L using an enzyme loading of 15 FPU/g poplar and a solid loading of 13.33 %. Furthermore, during pre-hydrolysis combined with simultaneous saccharification and fermentation (PSSF), an ethanol concentration of 37.58±0.23 g/L was achieved. Overall, this study demonstrates a novel ternary DES pretreatment method that effectively facilitates the fractionation and conversion of woody biomass into cellulosic ethanol. • A novel DES of TEBAC, TsOH, and EG was used in poplar pretreatment. • DES (TEBAC/TsOH/EG) removed 90.64±1.28 % lignin and 85.56±1.34 % xylan from poplar. • Cellulose digestibility of pretreated poplar was 15 times higher than untreated. • Ethanol yield of 117.70±0.74 mg/g poplar (37.58±0.23 g/L) achieved via PSSF.