Integrated understanding of enhancing enzymatic hydrolysis of bulrush through the metal chloride-assisting choline chloride: Glycerol pretreatment

Abstract

To improve the saccharification efficiency of bulrush, the supplementary of metal chlorides in pretreatment of lignocellulose had been researched. The effect of metal chloride type and dosage on the ability of deep eutectic solvent (DES ChCl: Gly) pretreatment was evaluated by composition analysis of biomass, characterization analysis [scanning electron microscope, Fourier transform infra spectra, X-ray diffraction, accessibility of cellulose (Direct red dye adsorption experiment), surface area of lignin (Azure B dye adsorption experiment)], and enzymatic saccharification. One-pot pretreatment of bulrush using the AlCl3/ChCl:Gly (molar ratio, 1:2:0.06) with the solid liquid ratio of 1:10 (w:w), lignin (70.8%) and hemicellulose (87.7%) could be effectively removed, and the enzymatic saccharification yield could reach 90.1%, much higher than that of raw bulrush (21.4%). AlCl3/ChCl:Gly pretreated bulrush showed an apparent reduction in lignin surface area due to lignin removal. The correlations between the Azure B dye adsorption data and delignification [Y(delignification) = 0.29 × X(surface area of lignin) + 226.9, R2 = 0.90] and glucose yield [Y(glucose yield) = −0.31 × X(surface area of lignin) + 247.9, R2 = 0.93] were observed during the AlCl3/ChCl:Gly pretreatment. This constructed pretreatment system could improve the bioconversion efficiency of bulrush, which had potential application in biorefinery of lignocellulose.