Liquid hot water pretreatment (LHWP) can convert hemicellulose in biomass into valuable xylooligosaccharides, but the utilization of glucan in the solid residue after hemicellulose extraction is usually constrained due to the significant lignin condensation during the LHWP. To alleviate lignin’s inhibition on glucan saccharification, this study established a variety of functional deep eutectic solvents (DESs) for the pretreatment of the solid residues after LHWP. The applied DES pretreatments resulted in different glucan saccharification yields. Under the premise of similar lignin removal, the ChCl/ethylene glycol (EG) system obtained near complete glucan digestibility, while the acid or alkali DESs had much lower enzymatic saccharification yields (35.7% and 20.6%). The mechanism of boosting the glucan saccharification by ChCl/EG was comprehensively analyzed by 2D-HSQC NMR, hydrophobicity, GPC and Langmuir adsorption isotherm of enzymes onto the cellulolytic enzyme lignin. Results indicated that lignin remaining in the ChCl/EG pretreated substrates had a lower hydrophobicity (2.8 L/g) and enzyme adsorption (4.6 mg/g), resulting from the EG grafting onto the α-position of the lignin side chain (as high as 5.0/100 Ar). The LHWP-DES pretreatment in this study unveiled the mechanism for cellulose digestibility enhancement using three common DESs and maximized the enzymatic hydrolysis yield, which provided a new scheme for the high-value utilization of biomass.

中文翻译：

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深共熔溶剂对缩合木质素的改性：深入了解改善酶促糖化的机制


液体热水预处理 （LHWP） 可以将生物质中的半纤维素转化为有价值的低聚木糖，但由于 LHWP 过程中明显的木质素缩合，半纤维素提取后固体残留物中葡聚糖的利用通常会受到限制。为了减轻木质素对葡聚糖糖化的抑制，本研究建立了多种功能性深共熔溶剂 （DES），用于 LHWP 后固体残留物的预处理。应用的 DES 预处理导致不同的葡聚糖糖化产量。在相似木质素去除的前提下，ChCl/乙二醇 （EG） 系统获得了接近完全的葡聚糖消化率，而酸或碱 DES 的酶糖化产率要低得多（35.7% 和 20.6%）。通过 2D-HSQC NMR、疏水性、GPC 和 Langmuir 吸附等温线综合分析酶对纤维素分解酶木质素的 ChCl/EG 促进葡聚糖糖化的机制。结果表明，由于 EG 接枝到木质素侧链的 α 位置（高达 5.0/100 Ar），残留在 ChCl/EG 预处理底物中的木质素具有较低的疏水性 （2.8 L/g） 和酶吸附 （4.6 mg/g）。本研究中的 LHWP-DES 预处理揭示了使用 3 种常见 DES 提高纤维素消化率的机制，并最大限度地提高了酶解产率，为生物质的高值化利用提供了新的方案。