Lv Xianqing, Yang Guangxu, Gong Zhenggang, Cheng Xin, Shuai Li, Huang Liulian, Chen Lihui, Luo Xiaolin, Liu Jing
College of Materials Engineering, Fujian Agriculture and Forestry University, Fuzhou, China.
Jiangsu Provincial Key Laboratory of Pulp and Paper Science and Technology, Nanjing Forestry University, Nanjing, China.
Front Bioeng Biotechnol. 2021 Nov 30;9:804456. doi: 10.3389/fbioe.2021.804456. eCollection 2021.
Chemical pretreatment followed by enzymatic hydrolysis has been regarded as a viable way to produce fermentable sugars. Phenylsulfonic acid (PSA) pretreatment could efficiently fractionate the non-cellulosic components (hemicelluloses and lignin) from bamboo and result in increased cellulose accessibility that was 10 times that of untreated bamboo. However, deposited lignin could trigger non-productive adsorption to enzymes, which therefore significantly decreased the enzymatic hydrolysis efficiency of PSA-pretreated bamboo substrates. Herein, poly(N-vinylcaprolactam) (PNVCL), a non-ionic surfactant, was developed as a novel additive for overcoming the non-productive adsorption of lignin during enzymatic hydrolysis. PNVCL was found to be not only more effective than those of commonly used lignosulfonate and polyvinyl alcohol for overcoming the negative effect of lignin, but also comparable to the robust Tween 20 and bovine serum albumin additives. A PNVCL loading at 1.2 g/L during enzymatic hydrolysis of PSA pretreated bamboo substrate could achieve an 80% cellulosic enzymatic conversion and meanwhile reduce the cellulase loading by three times as compared to that without additive. Mechanistic investigations indicated that PNVCL could block lignin residues through hydrophobic interactions and the resultant PNVCL coating resisted the adsorption of cellulase via electrostatic repulsion and/or hydration. This practical method can improve the lignocellulosic enzymatic hydrolysis efficiency and thereby increase the productivity and profitability of biorefinery.
化学预处理后进行酶水解被认为是生产可发酵糖的一种可行方法。苯磺酸（PSA）预处理可以有效地从竹子中分离出非纤维素成分（半纤维素和木质素），并使纤维素的可及性提高，是未处理竹子的10倍。然而，沉积的木质素会引发对酶的非生产性吸附，从而显著降低PSA预处理竹子底物的酶水解效率。在此，聚（N-乙烯基己内酰胺）（PNVCL），一种非离子表面活性剂，被开发为一种新型添加剂，用于克服酶水解过程中木质素的非生产性吸附。发现PNVCL不仅比常用的木质素磺酸盐和聚乙烯醇更有效地克服木质素的负面影响，而且与强大的吐温20和牛血清白蛋白添加剂相当。在PSA预处理竹子底物的酶水解过程中，PNVCL负载量为1.2 g/L时，可实现80%的纤维素酶促转化率，同时与无添加剂相比，纤维素酶负载量降低三倍。机理研究表明，PNVCL可以通过疏水相互作用阻断木质素残留，并且由此产生的PNVCL涂层通过静电排斥和/或水合作用抵抗纤维素酶的吸附。这种实用方法可以提高木质纤维素的酶水解效率，从而提高生物炼制的生产率和盈利能力。
