不同类型低共熔溶剂预处理对玉米秸秆酶解效率的影响

为探索不同类型低共熔溶剂（DES）预处理提高生物质酶解效率的机制，该研究选取两类DES即酸性（氯化胆碱(ChCl)-乳酸(Lac)、甜菜碱(B)-Lac）和碱性DES（ChCl-乙醇胺(M)、ChCl-N-(2-羟乙基)乙二胺(CN-2)）预处理玉米秸秆，对比研究不同酸碱性的DES对玉米秸秆组分和酶解效果的影响。研究表明碱性DES预处理和酶解效果较好，多糖含量从未处理时51.59%提高到81.33%~83.36%，木质素去除率71.35%~89.72%，多糖降解较为完全。红外光谱显示预处理中大量木质素和半纤维素的链接键发生断裂，糖苷键吸收峰显著增强；X-射线衍射表明玉米秸秆结晶度数值由32.99增至处理后的53.60，但晶体结构未改变。与酸性DES相比，碱性DES处理后外观色泽较浅，扫描电镜显示与未处理相比，预处理后的纤维疏松且粗糙。两类DES均是高效的预处理溶剂，碱性DES除本身碱性外，还可选择性的去除木质素，破坏半纤维素和木质素间链接键，纤维素与酶的接触面增大，从而酶解效率显著提高。该研究为生物质预处理新型DES溶剂的设计和选择提供一定的理论参考。

Effects of Different Deep Eutectic Solvent Pretreatments on the Efficiency of Corn Stover Enzymolysis

To elucidate the mechanism by which deep eutectic solvent (DES) pretreatments improve enzymolysis efficiency, acidic (choline chloride-lactic acid (ChCl-Lac), betaine (B)-Lac), alkaline (ChCl-ethanolamine (ChCl-M), and ChCl-N-(2-hydroxyethyl) ethylenediamine (ChCl-N-2)) DESs were used to pretreat corn stover and the effects of acidic/basic DESs on corn stover composition and enzymolysis efficiency were compared. Results indicated that alkaline DES is more effective in improving enzymolysis efficiency, with increased polysaccharide content (from 51.59% (untreated) to 81.33%~83.36%), lignin removal rates of 71.35%~89.72%, and the near-complete degradation of all polysaccharides. Fourier transform infrared (FT-IR) analysis indicated that pretreatment cleaved many of the lignin-hemicellulose bonds and enhanced the absorption peak associated with glycosidic bonds. X-ray diffraction (XRD) analysis demonstrated an increase in the crystallinity index (CrI) of corn stover following pretreatment, from 32.99 to 53.60, with no associated changes in the crystal structure. Furthermore, corn stover that is pretreated with alkaline DESs is lighter in color than that treated with acidic DESs, and scanning electron microscopy (SEM) indicated that DES-pretreated corn stover comprises looser and coarser fibers than untreated corn stover. Although acidic and alkaline DESs are both highly efficient pretreatment solvents, the intrinsic alkalinity of the latter renders it able to selectively remove lignin, cleave hemicellulose-lignin bonds, and increase the area of contact between the cellulose and biodegradation enzymes, greatly increasing the enzymolysis efficiency. The findings of this study are expected to serve as a theoretical reference for the design and selection of novel biomass pretreatment DESs.