Enhanced stability of Thermus thermophiles SG0.5JP17-16 laccase immobilized by CuF-MOF and its application in the Congo red decolorization

Abstract

Laccase attracts the extensive attention in degradation of pollutants due to its environmental friendliness and high efficiency. Free laccase has the disadvantages of easy inactivity, poor stability and difficulty in reuse, so its application in industry is confined. The immobilization of laccase can protect the laccase and actualize the cycle. In this work, copper fumarate metal-organic-frameworks (CuF-MOFs) were prepared and utilized to immobilize the Thermus thermophiles SG0.5JP17–16 laccase (lacTT) by encapsulation and surface adsorption at room temperature. The results from SEM, FTIR, XRD and BET indicated that lacTT was immobilized successfully. The optimal pH and temperature of lacTT@CuF-MOF and lacTT#CuF-MOF were determined to be pH 6.5 at 95 ℃ and pH 5.0 at 95 ℃ respectively. The immobilized laccase had the elevated stability in storage and reuse. The lacTT@CuF-MOF displayed higher thermal stability as compared with lacTT#CuF-MOF. But the Vmax (11.15 μM.min−1) value of lacTT@CuF-MOF was lower than that of lacTT#CuF-MOF (Vmax = 37.61 μM.min−1). The degradation efficiencies of lacTT@CuF-MOF and lacTT#CuF-MOF on Congo red were 41 % and 30 % at 6th cycle respectively. Therefore, the MOF was beneficial and could serve as sustainable carrier for laccase immobilization. The immobilized laccase might be more efficient to degrade the dyes in wastewater from textile industry than free enzyme.