Characteristics of Trametes villosa laccase adsorbed on aluminum hydroxide

The interaction of metal oxides with extracellular enzymes may influence humus formation and bioremediation processes. In this study, short-range ordered aluminum hydroxide exhibited a strong affinity for laccase from Trametes villosa (Xm = 6.18 μg mg−1) as evidenced by an H-type adsorption isotherm. Based on oxygen uptake measurements, free laccase had only slightly greater kinetic parameters (Km = 0.18 mM; Vmax = 14.35 mmol O2 min−1) than those of adsorbed laccase (Km = 0.15 mM; Vmax = 12.77 mmol O2 min−1). Free and adsorbed laccase showed similar activities under various pH conditions (from 3.8 to 7.8) and also showed similar activity loss over time (0–30 days). Adsorbed laccase was less resistant to thermal (4–100 °C) and proteolytic degradation, but also less sensitive to inhibition by humic acid than free laccase. Attenuated total reflectance infrared (ATR-IR) spectroscopy did not show significant changes in the secondary structure of laccase due to adsorption on aluminum hydroxide. These results indicate that laccase in soil may be found predominantly complexed with short-range ordered aluminum hydroxide, and laccase activity and stability is little affected by adsorption to the mineral. Consequently, use of immobilized enzymes such as laccase on aluminum hydroxide can be considered a practical tool for soil remediation.