基于乳酸的深度共熔溶剂提取秸秆木质素对纤维素酶水解效率的影响

doi:10.16085/j.issn.1000-6613.2021-2364

摘要/Abstract

摘要：

基于乳酸的深度共熔溶剂（DES）在脱木素和木质纤维素转化方面显示出巨大潜力。本文以乳酸为氢键供体（HBD），氯化胆碱、盐酸胍、精氨酸、甜菜碱盐酸盐为氢键受体（HBA）合成了4种DES，并分别提取了木质素，对比研究了4种木质素对微晶纤维素酶水解效率的影响。结果表明，4种DES提取木质素的疏水性与其对酶蛋白吸附能力线性正相关，而两者与木质素与酶水解效率呈线性负相关性。非特异性吸附是该类木质素抑制纤维素酶水解效率最重要的因素，而疏水性作用则是引起酶蛋白吸附的主要原因。结构分析表明木质素的脂肪族羟基和酚羟基主导的氢键相互作用是促进酶蛋白吸附、降低酶水解效率的原因之一。此外，由羧基产生的静电斥力对纤维素酶水解效率的影响较弱。随着DES提取木质素能力的增强，木质素的羟基和羧基含量逐渐增高，其对纤维素酶的抑制作用增大。氯化胆碱-乳酸因其优良的木质素提取和生物质解构能力，提取的木质素对酶的抑制作用最强，其次是乳酸-盐酸胍和乳酸-甜菜碱盐酸盐，最后是乳酸-精氨酸。

关键词: 溶剂, 木质素纤维素生物质, 木质素, 酶, 吸附（作用）, 抑制效应

Abstract:

Lactic acid-based DES has shown great capability in removal of lignin from biomass and conversion of lignocellulose to fuels, chemicals and materials. In this work, lignin was extracted by four DESs, in which lactic acid was used as hydrogen bond donor (HBD) and choline chloride, guanidine hydrochloride, arginine or betaine hydrochloride was used as the hydrogen bond acceptor (HBA), and its effect on the hydrolysis efficiency of Avicel was studied. The results showed that the adsorption capacity of lignin towards cellulase shows a good linear positive correlation with the hydrophobicity of lignin, and both of them are linearly negatively correlated with the enzymatic hydrolysis efficiency of Avicel. The non-specific adsorption of lignin towards protein was the major cause of the inhibition, and the hydrophobic effect is mainly responsible for the adsorption of enzymes on lignin. Furthermore, the structural analysis of lignin revealed that the hydrogen bond interaction of aliphatic hydroxyl groups, phenolic hydroxyl groups, and the amino acids residues of proteins was the reason for promoting enzyme protein adsorption and reduced enzyme hydrolysis efficiency. Besides, the electrostatic repulsion generated by carboxyl group of lignin had weak effect on the hydrolysis efficiency of cellulase. DES with strong deconstruction severity may cause high hydroxyl group content, which always lead to strong inhibition of cellulase. Lactic acid/ choline chloride (LC) had the strongest inhibitory effect on enzyme due to its excellent lignin extraction and biomass deconstruction ability, followed by lactic acid guanidine hydrochloride and lactic acid betaine hydrochloride, and finally lactic acid arginine. This work is expected to improve the fundamental understanding of the knowledge of DES application in the field of biorefinery,and lay a foundation for the development of novel solvents-driven lignocellulosic biomass refining.

Key words: solvents, lignocellulosic biomass, lignin, enzyme, adsorption, inhibitory effect

中图分类号:

TQ353

蒲福龙, 伍尚炜, 郑映玲, 郑玉意, 侯雪丹. 基于乳酸的深度共熔溶剂提取秸秆木质素对纤维素酶水解效率的影响[J]. 化工进展, 2022, 41(9): 4937-4945.

PU Fulong, WU Shangwei, ZHENG Yingling, ZHENG Yuyi, HOU Xuedan. Effect of lignin extracted by lactic acid-based deep eutectic solvent from rice straw on cellulase hydrolysis efficiency[J]. Chemical Industry and Engineering Progress, 2022, 41(9): 4937-4945.

图/表 10

图1 微晶纤维素酶水解过程曲线

图2 木质素对纤维素酶蛋白的Langmuir吸附作用

表1 Langmuir吸附等温线参数

样品	Г_max/mg∙g^-1	K/mL∙mg^-1	R/L∙g^-1
L-LC	46.35	3.39	0.157
L-LGH	29.81	5.57	0.166
L-LArg	4.52	5.69	0.026
L-LBH	25.79	2.47	0.064

图3 最大酶吸附量与微晶纤维素酶水解效率的关系

表2 木质素疏水性数据

样品	疏水性/L∙g^-1	R²
L-LC	0.0153	0.9874
L-LGH	0.0112	0.9856
L-LArg	0.0332	0.9874
L-LBH	0.0103	0.9262

图4 木质素对酶蛋白的最大吸附量与木质素疏水性的关系

图5 木质素的红外光谱

图6 木质素的HSQC图谱methoxy—甲氧基结构；A（Aα、Aγ）—β-O-4醚键结构；B（Bβ）—树脂醇结构；C（Cγ）—苯基香豆素结构；Ara（Ara(2，3，4)、Ara5）—阿拉伯糖结构；Xyl（Xyl4）—木糖结构；G（G2、G5、G6）—愈创木基结构；S（S2，6、S2,6cond’）—紫丁香结构；H（H2，6）—对羟苯基结构；PCA（PCAβ、PCA2,6）—愈创木基结构；FA（FAβ）—阿魏酸结构

图7 羟基含量与酶解效率、酶蛋白最大吸附量的关联图虚线—脂肪族羟基和总羟基含量与葡萄糖释放量的线性拟合曲线；实线—酚羟基和总羟基含量与酶蛋白最大吸附量的线性拟合曲线

图8 羧基含量对酶解效率、木质素疏水性和木质素对酶蛋白的最大吸附量的影响虚线—羧基含量与葡萄糖释放量的线性拟合曲线；实线—羧基含量与酶蛋白最大吸附量的线性拟合曲线

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