Degradation of 2,4-DCP by the Immobilized Laccase on the Carrier of Fe304@SiO2-NH2

In this paper, the laccase immobilized on Fe304@SiO2-NH2 nanoparticles was successfully prepared by the glutaraldehyde cross-linking method. The degradations of 2,4-diehlorophenol （2,4-DCP） catalyzed by laccase and immobilized laccase were carried out. The optimal conditions regarding degradation efficiency were also discussed, which include reaction time, pH value, temperature, concentration of 2,4-DCP and laccase. When laccase was immobilized on Fe304@SiO2-NH2 carrier by crosslinking with glutaraldehyde, the stability and repetition were im- proved significantly. The removal efficiency of 2,4-DCP by immobilized laccase still remained over 59% after six cycles of operation. Degradation of 2,4-DCP is a first-order reaction and the activation energies of 2,4-DCP catalyzed by laccase and immobilized laccase are 51.93 kJ·mol-1 strate the immobilized laccase had a faster degradation Fe304@MSS-NH2 can promote the degradation reaction. and 44.12 kJ·mol-1, respectively. The results demonrate than the free laccase; the magnetic carrier

Influence of counteranions on catalytic ability of immobilized laccase in Cu-alginate matrices: Inhibition of chloride and activation of acetate

Laccase is a promising oxidase with environmental applications, such as lignin degradation and chlorophenol detoxification. Laccase immobilization can significantly improve physiochemical stability and reusability compared to the free enzymes. In this work, anion effect was investigated in entrapment of Cu-alginate matrix with five types of anions, including perchlorate （ClO4）, nitrate （NO3）, sulfate （SO42 ）, chloride （Cl）, and acetate （CH3CO2-）. Accordingly, chloride inhibition and acetate activation were detected in the o-tolidine kinetic experiments, while effects of the other three anions were much smaller. Such counteranion effects were also observed in the laccase-catalyzed biodegradation of 2,4- dichlorophenol. The results indicated that counteranions in the enzyme immobilization process are crucial for catalytic capacity, probably due to the competition with the carboxylate groups in alginate. Our results also imply that these anions might coordinate the copper cations in laccase.

Enhancing laccase stability and activity for dyes decolorization using ZIF-8@MWCNT nanocomposite

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.

Immobilization of laccase on organic–inorganic nanocomposites and its application in the removal of phenolic pollutants

Polydopamine-functionalized nanosilica was synthesized using an inexpensive and easily obtainable raw material,mild reaction conditions,and simple operation.Subsequently,a flexible spacer arm was introduced by using dialdehyde starch as a cross-linking agent to bind with laccase.A high loading amount(77.8 mg∙g^(‒1))and activity retention(75.5%)could be achieved under the optimum immobilization conditions.Thermodynamic parameters showed that the immobilized laccase had a lower thermal deactivation rate constant and longer half-life.The enhancement of thermodynamic parameters indicated that the immobilized laccase had better thermal stability than free laccase.The residual activity of immobilized laccase remained at about 50.0%after 30 days,which was 4.0 times that of free laccase.Immobilized laccase demonstrated excellent removal of phenolic pollutants(2,4-dichlorophenol,bisphenol A,phenol,and 4-chlorophenol)and perfect reusability with 70% removal efficiency retention for 2,4-dichlorophenol after seven cycles.These results suggested that immobilized laccase possessed great reusability,improved thermal stability,and excellent storage stability.Organic–inorganic nanomaterials have a good application prospect for laccase immobilization,and the immobilized laccase of this work may provide a practical application for the removal of phenolic pollutants.

Immobilization of laccase by Cu^(2+) chelate affinity interaction on surface modified magnetic silica particles and its use for the removal of pentachlorophenol

Magnetic Cu^（2＋）-chelated silica particles using polyacrylamide as a metal-chelating ligand was developed and used for the immobilization of laccase by coordination.The effect of pH and temperature on the enzymatic property of immobilized laccase and its catalytic capacity for pentachlorophenol（PCP） degradation were evaluated systemically.Compared with free laccase,the immobilized laccase showed improved acid adaptabihty and thermal stability.The immobilized laccase prepared in this work exhibited a good catalytic capacity for PCP removal from aqueous solutions.