Comparison of enzymatic degradation of tetracycline hydrochloride by laccases from different sources

BACKGROUND

Enzymatic degradation has been recognized as an efficient and environmentally-friendly method for pollutant removal, and has attracted increasing attention. Here, the catalytic removal of tetracycline hydrochloride (TC·HCl) from water using two different sources of laccase (EC 1.10.3.2), Rhus vernicifera laccase (L_Rv) and Aspergillus oryzae laccase (L_Ao), is comparatively evaluated for the first time, and the role of ABTS as a mediator is studied.

RESULTS

In the presence of ABTS, the laccases can effectively remove TC·HCl and its antibiotic activity in weakly acidic environments (pH 4.0–6.0). The efficiency of TC·HCl degradation in the L_Ao-ABTS system was much higher than that in the L_Rv-ABTS system. When the concentrations of laccase, TC·HCl and ABTS were 60, 20 and 15 mg L⁻¹, respectively, the former degraded 71.3% of TC·HCl at 20 °C and pH 4.0 in 5 h, whereas the latter only degraded 35.1% of TC·HCl. At a molar ratio of ABTS to TC·HCl of 2, L_Ao completely degraded TC·HCl within 3 h. However, ABTS was consumed in the L_Ao system and not in the L_Rv system. In the L_Ao-ABTS system, L_Ao concentration, pH value and visible light irradiation significantly affected TC·HCl degradation whereas they only had a slight effect in the L_Rv-ABTS system. Additionally, the degradation pathways of TC·HCl are more complex in the L_Ao-ABTS system.

CONCLUSION

This study indicates that there are significant differences in the mechanisms and influencing factors of two different sources of laccase for removing antibiotics from water, which helps to promote the application of laccase in environmental bioremediation. © 2025 Society of Chemical Industry (SCI).