Immobilization Of Laccase From Marine Bacteria And Its Decolorization Of Textile Dyeing Wastewater

Because of its large emissions, complex structure, poor biodegradability, textile mill effluents cause serious harm to the ecological environment and human health. Dyeing wastewater treatment has become a hot and difficult topic in the field of environment. Laccases are copper-containing polyphenol oxidases, with a wide range of catalytic substrates efficiency, low cost, environmentally friendly, and have great potential on dyeing wastewater treatment, papermaking wastewater treatment, medicine and other fields.In this experiment, the enzymatic properties of the free enzyme from marine bacteria were studied, the results showed that the optimum temperature for the free enzyme is45℃, the optimum pH is7.5. Thermal stability of the free enzyme is poor. When heated at a thermostat water bath of50℃for lh, laccase completely lost its activity. Compared with fungal laccase, the bacterial laccase exhibits high stability in the alkaline solution. The activity of laccase is more than80%in the range of pH6.0-9.0. This indicted that laccase has broad application prospects in alkaline wastewater treatment containing dyeing wastewater, papermaking wastewater. The half-life of uncontaminated laccase activity is9d, while contaminated laccase is only2d, the possible reason is that the laccase is susceptible to contamination by other substances, and is seen as nutrients by some bacteria, which causes the quantity of enzyme protein a significant reduction, resulting in a great fall in enzyme activity.Laccase from marine bacteria was immobilized by sodium alginate-PVA carrier. Immobilization laccase has high mechanical strength, which has a larger value in the actual wastewater treatment. Both Alginate and CaCl2perform inhibition of bacterial laccase, inhibitory effect of0.15mol/1of CaCl2on laccase is strongest; while the PVA can improve laccase activity. After enzyme was immobilized, the optimum temperature and pH did not change, but the immobilized enzyme had a stronger adaptability to high temperature. Immobilization efficiency of laccase on the carrier is83%. Immobilized laccase maintained about20%activity after six reaction cycles.Three different types of dyes were degraded by free enzyme. The results showed that under optimum conditions(20℃, pH7.5, the concentration of enzyme20U/L, dye concentration20mg/l, reaction time2d), laccase showed a very high decolorization efficiency towards azo dye reactive red24, decolorization rate was about88%, while the decolorization rate of triarylmethane dyes bromocresol green is low, only about8%; anthraquinones dye reactive brilliant blue X-BR could not be decolorized by laccase. Laccase also performed high decolorization ability for high concentrations of reactive red24.In three days,80%of 160mg/1reactive red24have been degraded. Mediator ABTS almost has no effect on the dye decolorization.Dye decolorization by immobilized laccase is a common effect of physical adsorption and enzymatic catalysis. Immobilized laccase degraded reactive red24in a continuous operation experiment. The results showed that dye decolorization rate of immobilized enzyme was1-16%every day when the dye concentration was640mg/1. The life of the immobilized enzyme can reach13d, about two times more than free enzyme.