Purification and biochemical characterization of two laccase isoenzymes isolated from Trichoderma harzianum S7113 and its application for bisphenol A degradation

Two laccase isoenzymes (LacA and LacB) were isolated from a novel Trichoderma harzianum S7113 isolate employing ammonium sulfate precipitation, Sephadex G100, and DEAE Sepharose ion exchange chromatography. The molecular weights of the purified LacA and LacB laccases were estimated to be 63 and 48 kDa, respectively. The two isoenzymes had their optimum activities at the same temperature (50 ? ), but at slightly different pH values (pH 3.0 for LacA and pH 2.5 for LacB). LacA and LacB had the same thermal stability at 40 ? and pH stability at pH 9.0. The two isoenzymes also showed a high level of specific activity toward ABTS, where the K-m values of LacA and LacB were 0.100 and 0.065 mM, whereas their V-max values were 0.603 and 0.182 mu mol min(-1), respectively. LacA and LacB catalytic activity was stimulated by Mg2+, Zn2+, K+, and Ni2+, whereas it was inhibited by Hg2+ and Pb2+, beta-mercaptoethanol, EDTA, and SDS, and completely inhibited by sodium azide. Our findings indicate that purified laccase has a promising capacity for bisphenol A (BPA) bioremediation across a broad pH range. This finding opens up new opportunities for the commercialization of this technique in a variety of biotechnology-based applications, particularly for removing endocrine chemicals from the environment.

Automated summary

Two laccase isoenzymes (LacA and LacB) were isolated and purified from Trichoderma harzianum S7113. LacA had a molecular weight of 63 kDa, while LacB had a molecular weight of 48 kDa. Both isoenzymes exhibited optimum activity at 50℃, but at slightly different pH values. They also showed similar thermal and pH stability. LacA and LacB had high specific activity toward ABTS, with LacB having a lower K-m and V-max value than LacA. The catalytic activity of both isoenzymes was affected by various ions, and completely inhibited by sodium azide.