An efficient material (Mn–Cu-AC/cellulose beads) for immobilizing laccase: excellent activity, high stability and effective pollutant removal rate

Abstract

Laccase immobilization is an effective way to realize the industrial application of laccase, but the loss of immobilized laccase activity is serious, which is an urgent problem to be solved. In this study, a novel laccase immobilization material was prepared by mixing waste Mn–Cu-loaded activated carbon with cellulose solution and regenerated in hydrochloric acid solution, which significantly improved the immobilized laccase activity. The optimum immobilization conditions (T, pH and initial laccase concentration) of Mn–Cu-AC/cellulose beads (Mn–Cu-ACC) for laccase were studied by the response surface method. Under the optimum conditions (T = 43 °C, pH = 4.0 and c = 6.8 g L⁻¹), immobilized laccase (Laccase@Mn–Cu-ACC) showed excellent performance in terms of pH stability, thermostability and storage stability. And the enzyme activity of the laccase immobilized on the Mn–Cu-ACC carrier remarkably increased by 29.6% compared to that of the ACC. At last, the Laccase@Mn–Cu-ACC was used for the degradation of bisphenol A (BPA). Under the optimum conditions (t = 5.5 h, T = 45 °C, pH = 4.0 and initial c_BPA = 70 mg L⁻¹), the removal rate of BPA reached 72.3% in the first cycle, and after 5 cycles of reusing the immobilized laccase, the relative removal rate of BPA was retained at 53.2% of the initial removal rate. This study developed a new type of immobilized laccase carrier and provided a new path for the application of waste heavy metal loaded activated carbon.