The continuous use of chemical dyes in various industries,and their discharge into industrial effluents,results in severe problems to human life and water pollution.Laccases have the ability to decolorize dyes and toxic chemicals in industrial effluents as green biocatalysts.Their possible industrial applications have been limited by poor reusability,low stability,and loss of free laccase action.In this research,lac-case was immobilized on zeolitic imidazolate framework coated multi-walled carbon nanotubes(Laccase@ZIF-8@MWCNTs)via metal affinity adsorption to develop an easy separable and stable enzyme.The optimum reaction conditions for immobilized laccase are at a pH of 3.0 and a temperature of 60℃.The immobilized laccase was enhanced in storage and thermal stability.The results indicated that Laccase@ZIF-8@MWCNTs still maintained 68%of its original activity after 10 times of repeated use.Most importantly,the biocatalytic system was applied for decolorization of different dyes(20 mg·L^(-1))without a mediator,and up to 97.4%for Eriochrome black T and 95.6%Acid red 88 was achieved in 25 min.Biocatalysts with these properties may be used in a variety of environmental and industrial applications.
Pascal HabimanaYanjun JiangJing GaoJean Bernard NdayambajeOsama M.DarweshJean Pierre MwizerwaXiaobing ZhengLi Ma
Cross-linked enzyme aggregates(CLEAs) of nitrile hydratase(NHase) ES-NHT-118 from Escherichia coli were prepared by using ammonium sulfate as precipitating agent followed by cross-linking with dextran polyaldehyde for the first time. In this process, egg white was added as protein feeder for facilitating the formation of CLEAs. The optimal conditions of the immobilization process were determined. Michaelis constants(Km) of free NHase and NHase CLEAs were also determined. The NHase CLEAs exhibited increased stability at varied pH and temperature conditions compared to its free counterpart. When exposed to high concentrations of acrylamide, NHase CLEAs also exhibited effective catalytic activity.
Liya ZhouHaixia MouJing GaoLi MaYing HeYanjun Jiang
