漆酶介体系统催化碱木质素降解及其结构演变研究

Catalytic Degradation of Alkali Lignin by Laccase Mediator System and Its Structural Evolution Studies

漆酶介体系统(Laccase-mediator system,LMS)以介体为电子穿梭体,对底物有较高的催化效率,被广泛应用于环境污染物的降解。本研究系统探究了漆酶及漆酶/H_(2)O_(2)、漆酶/HBT (1-羟基苯并三唑)和漆酶/ABTS (2,2’-联氮双(3-乙基苯并噻唑啉-6-磺酸)二铵盐) 3种介体系统对碱木质素的降解效果,探究了漆酶/ABTS介体系统降解碱木质素的影响因素,并对漆酶和3种LMS反应前后的碱木质素进行了结构表征分析。结果表明,漆酶/ABTS介体系统的碱木质素降解率最高,在32℃、pH值=5、ABTS浓度2 mmol/L、反应时间24 h的条件下,碱木质素降解率可达39%;漆酶处理所得碱木质素的官能团种类未发生变化,但多分散系数减小,分子质量增加;LMS处理所得碱木质素的多分散系数和分子质量进一步减小,尤其是漆酶/ABTS处理后,碱木质素的数均分子质量减少了50.5%;LMS处理后碱木质素化学键发生了不同程度的断裂,引起了C—O、β-O-4连接键断裂,脱甲基反应,苯环开环等变化。

Laccase-mediator system(LMS),which uses the mediator as an electron shuttle,has been widely used in the degradation of environmental pollutants because of its higher catalytic efficiency for substrates.This study systematically investigated the degradation effects of laccase and laccase/H_(2)O_(2),laccase/HBT(1-hydroxybenzotriazole)and laccase/ABTS(2,2’-bisazobis(3-ethylbenzothiazolin-6-sulfonic acid)diammonium salt)on alkali lignin,and explored the influencing factors of laccase/ABTS mediator system on degradation of alkali lignin.The structural characterization of alkali lignin before and after the reaction with laccase and the three LMS was also analyzed.The results showed that the highest degradation rate of alkali lignin was achieved by the laccase/ABTS mediator system,which could reach 39%under the reaction conditions at 32℃for 24 h with pH valve of 5,and ABTS concentration of 2 mmol/L.The types of functional groups of alkali lignin obtained from the laccase treatment remained unchanged,but the polydispersity coefficient was decreased and the molecular mass was increased;and the polydispersity coefficient and the molecular mass of alkali lignin obtained from the LMS treatment were further decreased,especially the polydispersity coefficient and the molecular mass of alkali lignin obtained from the LMS treatment.In particular,the number average molecular weight of alkali lignin was reduced by 50.5%after laccase/ABTS treatment;the chemical bonds of alkali lignin were broken to different degrees after LMS treatment,which induced changes such as C—O andβ-O-4 linkage breaking,demethylation reaction,and benzene ring-opening.