Immobilization Of Recombinant CotA Laccase And Its Application In Decolorization Of Textile Dyes

In this study,recombinant CotA laccase was immobilized with sodium alginate-calcium chloride embedding,GO-nFe₃O₄ adsorbing and admixture combined sodium alginate-calcium chloride with GO-nFe₃O₄ and the three methods were compared with.The results showed that the immobilization rate of embedding method,adsording method and admixture method was 33.25%,92.46% and 100%,respectively.We studied the enzymatic properties of both immobilized laccases and free laccase,and the results showed that the optimum pH of the three immobilized laccases and free laccase was different at all and the immobilization of laccase by different materials resulted in the shift of the optimum pH.The immobilization enhanced the pH stability of laccase.The optimum temperature of immobilized laccases and free laccase was 60°C.The immobilization failed to enhance the thermal stability of laccase,and free laccase showed higher thermal stability than immobilized laccases.Immobilized laccases showed high tolerance towards metal ions,inhibitors,detergents,and organic solvents.Experiments examining the decolorization of dyes?RBBR,Congo red,Malachite green and Indigo carmine?by immobilized laccases and free laccase were carried out.The results indicated that immobilized laccases showed a higher decolorization capacity than free laccase,and support adsorption played an important role in the removal of dyes.The decolorization of Malachite green and Indigo carmine by three immobilized laccases and free laccase had no big difference and the decolorization ratio was above 97% in 2h.The decolorization ratio of RBBR and Congo red by admixture was 95.99% and 97.81%,respectively,which was the highest than the other two methods and free laccase.The decolorization of Malachite green by embedding method,adsording method and free laccase was 88%,48% and 80%,respectively,while Congo red was 96%,84% and 82%,respectively.The decolorization by embedding method was apparently higher than by adsording method.The reuse potential of decolorizing dyes by immobilized laccases was studied.The results showed that immobilized laccase by admixture showed high potential for reuses with 60.65% and 67.08% of immobilization ratio after 10 cycles for RBBR and 20 cycles for Congo red,respectively;and with 97% and 94% after 50 cycles for Malachite green and Indigo carmine,respectively.The embedding method immobilized laccase showed high potential for reuses with 60% of immobilization ratio after 7 cycles for RBBR and 18 cycles for Congo red;and above 90% of immobilization ratio after 50 cycles for Malachite green and Indigo carmine.The absorbing method immobilized laccase showed lower potential for reusability with 24% and 51% of immobilization ratio after 3 cycles for RBBR and 4 cycles for Congo red,respectively;and with 66% and 49% after 17 and 13 cycles for Malachite green and Indigo carmine,respectively.Immobilized laccases by admixture method and embedding method showed high potential for reusability and high stability even after many consecutive uses which showed huge potential for the treatment of wastewater and textile dye effluents.