Ultrasound-assisted biomimetic mineralization immobilization improves the stability and catalytic performance of laccases derived from Bacillus licheniformis

Abstract

Currently, there is less research on the biomimetic mineralization immobilization of bacterium-derived laccase as an organic component and noncopper-based inorganic salts as an inorganic component. In this study, a method for rapid biomimetic mineralization immobilization of Bacillus licheniformis-derived laccase was explored to improve its stability and catalytic performance. The type and concentration of metal ions, enzyme concentration, and ultrasonication time were optimized. Finally, the optimal immobilization conditions for the laccases were 1 mM Ni²⁺ mixed with 0.1 mg·mL⁻¹ laccases and sonication for 15 min. Under these conditions, the highest enzyme activity recovery rate was 453 %. The immobilized laccase exhibited a nanospherical structure. After immobilization, the half-life of the enzyme activity increased from 40 min to 50 min at 50°C. The free enzyme retained only 43 % of the relative activity after 8 days of storage (25°C), whereas the immobilized enzyme retained over 60 % of the relative activity. Furthermore, the catalytic efficiency of the immobilized enzyme reached 29.844 s⁻¹·μM⁻¹, which was 3.5 times greater than that of the free enzyme. The specific activity increased from 28.49 U·mg⁻¹ to 83.86 U·mg⁻¹. Our study would provide a methodological reference for the immobilization of laccases derived from bacteria and promote the practical application of laccases.