Abstract
In this work, amidoxime polyacrylonitrile (AOPAN) nanofibrous membrane was prepared by a reaction between PAN nanofibers and hydroxylamine hydrochloride. The AOPAN nanofibrous membranes were used for four metal ions (Fe3+, Cu2+, Ni2+, Cd2+) chelation under different conditions. Further, the competition of different metal ions coordinating with AOPAN nanofibrous membrane was also studied. The AOPAN chelated with individual metal ion (Fe3+, Cu2+, Ni2+, Cd2+) and also the four mixed metal ions were further used for laccase (Lac) immobilization. Compared with free laccase, the immobilized laccase showed better resistance to pH and temperature changes as well as improved storage stability. Among the four individual metal ion chelated membranes, the stability of the immobilized enzymes generally followed the order as Fe–AOPAN–Lac > Cu–AOPAN–Lac > Ni–AOPAN–Lac > Cd–AOPAN–Lac. In addition, the immobilized enzyme on the carrier of AOPAN chelated with four mixed metal ions showed the best properties.
Highlights
Laccase is a copper-containing enzyme that can catalyze the oxidation of a wide variety of substrates with the concomitant four electron reduction of oxygen to water [1,2]
The SEM images of the PAN and Amidoxime polyacrylonitrile (AOPAN) nanofibers are shown in Figure 2a,b, respectively
It could be observed that activities of both free and immobilized laccase were strongly dependent on temperature, and the maximal activity was exhibited at 50 °C
Summary
Laccase is a copper-containing enzyme that can catalyze the oxidation of a wide variety of substrates with the concomitant four electron reduction of oxygen to water [1,2]. It has been realized that free enzymes have the weakness of non-recyclability, and reusability in industrial applications. Various methods concerning laccase immobilization have been reported, including entrapment, encapsulation, adsorption, covalent binding, as well as self-immobilization [9]. As far as we are concerned, metal ion chelated AOPAN nanofibers have not been used for laccase immobilization yet. Four different metal ions (Fe3+, Cu2+, Ni2+, Cd2+) were chelated by AOPAN nanofibrous membranes. The AOPAN nanofibrous membrane chelated with these four mixed metal ions mentioned above was used as substrate to evaluate its ability in enzyme immobilization
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