尺寸可控的固定化漆酶-介体凝胶小球微反应器的制备和性能评价

Facile Synthesis and Evaluation of Size-tunable Immobilized Laccase-mediator Microreactor

首次利用漆酶-乙酰丙酮(AA)-过硫酸钾组成的复合引发体系在室温水相中引发丙烯酰胺的聚合,采用滴球法将上述反应液滴入硫酸铜溶液,利用铜离子与壳聚糖的络合交联反应制备得到尺寸可控的核壳结构小球.小球内部发生自由基聚合反应,将漆酶-AA同步固定于新生成的具有三维网络结构的水凝胶中.微反应器小球的形貌和内部孔道结构通过扫描电镜和氮气吸附实验进行了表征.该固定化漆酶-介体小球微反应器相比于游离漆酶表现出更高的p H稳定性和耐热性.得益于固定化AA的介导作用,漆酶的可重复使用性能得到显著提升,降解孔雀石绿的有效循环批次较游离漆酶-介体体系延长了3倍,为降低漆酶在实际废水处理中的成本、削减游离介体带来的二次污染提供了一条有效途径.

A series of immobilized laccase-mediator microreactor （LMMR） was prepared in a one-pot process by simultaneously immobilizing Trametes versicolor laccase and acetylacetone （AA） into size-tunable chitosan copper-polyacrylamide hydrogel beads. The polymerization was induced by a laccase-AA-persulfate ternary initiating system and was finished within the chitosan beads at room temperature. The preparation conditions for the LMMR were optimized by an orthogonal array design. The method developed in this work, for the first time, realized the coimmobilization of laccase and mediator in microreactors of tunable size and mechanic strength. Experimental results from scanning electron microscopy and nitrogen adsorption-desorption analysis indicate that the resulting LMMR had a core-shell structure. Chitosan copper served as the mechanical shell, whereas polyacrylamide hydrogel was the core of three-dimensional network. Throughout the hydrogel beads, there were abundant mesopores of size in the range of 2-8 nm. The microreactor beads could endure a 20 N pressure in the axial direction, ensuring the structural integrity in the practical application in wastewater. The loading efficiency of laccase in the microreactor reached up to 93.5%. As compared with the free laccase, the LMMR showed better storage stability and higher tolerance to changes in solution pH and temperature. In the enzymatic conversion of malachite green （MG）, benefited from the mediation effect of the immobilized AA, the LMMR still worked after 17 cycling runs （12 h for each cycle）, which was 3-fold longer than that of a free laccase-mediator system. The successful recovery of both laccase and mediator is promising to reduce the cost for the application of laccase in wastewater treatment and might be helpful to cut down the secondary pollution from free laccase mediators. These results demonstrate that this novel one-pot synthesis was a useful strategy in the immobilization of laccase. The LMMR has a great potential in large-scale application for dyeing effluent treatment.