碱木质素聚乙氧基接枝共聚物表面特性对纤维素酶糖化效率的影响

以碱木质素(AL)与聚乙二醇二缩水甘油醚(PEGDE)为原料,于80 ℃和150 r/min条件下,反应2 h,制备碱木质素-聚乙氧基接枝共聚物(PEGDE-AL),研究其对纤维酶的非生产性吸附性能和酶糖化效率的影响机制。X射线光电子能谱(XPS)、Zeta电位滴定和接触角测试的结果表明,碱木质素经过聚乙氧基接枝共聚改性后,表面元素组成发生了较大变化,氧元素与碳元素的比率由0.28增至1.56; 表面正电荷数目降低,亲水性能增强,使得纤维素酶与PEGDE-AL间吸附结合力较纤维素酶与AL间结合力降低了57%,酶蛋白与底物间的非生产性吸附能力下降。在水解体系中分别添加质量浓度为4 g/L的AL和PEGDE-AL,PEGDE-AL和微晶纤维素72 h的葡萄糖得率为50.67%,较碱木质素和Avicel水解体系72 h的葡萄糖得率增加了41.14%,且上清液中游离蛋白的质量分数增加了1.56倍。碱木质素经过聚乙氧基接枝共聚后,显著减弱了对纤维素酶的无效吸附,该研究结果可为优化现有的预处理技术提供理论基础。
The non-productive adsorption of cellulase enzyme on lignin can obviously decrease its efficiency on the enzymatic hydrolysis of lignocellulosic biomass. In this study, polyoxyethylene ether grafted alkali lignin(PEGDE-AL)was obtained by mixing alkali lignin(AL)with polyethylene glycol diglycidyl ether(PEGDE)at 80 ℃, 150 r/min for 2 h of reaction time. And the effects of PEGDE-AL on the non-productive adsorption of cellulase enzymes and enzymatic hydrolysis of Avicel were evaluated and analyzed. The results from XPS, Zeta potential and contact angle analysis showed that, after the modification of the AL by grafting poly oxyethylene, the surface groups on lignin were changed to some extent and the O/C ratio increased from 0.28 to 1.56. Compared with the AL, the values of surface positive charge and the hydrophobicity reduced in PEGDE-AL, which would result in the reduction of adsorption binding force between cellulase enzyme and PEGDE-AL. With the addition of 4 g/L AL and PEGDE-AL to enzymatic hydrolysis of Avicel, the 72 h hydrolysis yield of Avicel was 50.67% for PEGDE-AL, which increased by 41.14% compared with the enzymatic hydrolysis of Avicel and AL. And the content of free enzyme protein in supernatant increased by 1.56 times than that of the enzymatic hydrolysis of Avicel and AL. All the results indicated the formation of functional factors on lignin moieties, which could alleviate the irreversible adsorption of cellulose and consequently be responsible for the promoting of enzymatic digestibility efficiency. The results from this study could help to optimize the existing pretreatment methods as well as to develop new pretreatment technologies that lead to less lignin inhibitory