A novel lignin peroxidase-mimicking by CoO-Co2VO4/C nanocomposite and its application in sensing fungal metabolite veratryl alcohol.

Various types of peroxidase mimics have been reported so far, among which horseradish peroxidase (HRP) mimicking nanozymes have been the most intensively studied. Lignin peroxidase (LiP), a main lignin-biodegrading enzyme class, is relatively complex to extract from white-rot fungi and suffers from poor stability and easy denaturation. Herein, we report a CoO-Co2VO4/C nanocomposite with nanosphere and flaky flower structure prepared by a simple one-step solvothermal method, which exhibits both excellent LiP-like and HRP-like activities. This LiP-mimicking nanozyme can catalyze H2O2 to selectively oxidize the common model substrate veratryl alcohol (VA) to veratraldehyde. Interestingly, the LiP-like activity outperforms at pH 8.0 with the catalytic mechanism originating from oxygen vacancies, while the HRP-like activity is excellent at pH 4.0 with the catalytic mechanism originating from singlet oxygen. CoO-Co2VO4/C strictly follows the enzymatic kinetics with a high catalytic rate. H2O2 is both an activator and an inhibitor of the LiP mimic. Based on this LiP-mimicking activity, a sensitive and rapid VA sensing platform was established. The sensing platform achieved a detection limit for VA of 0.021 mM. Furthermore, the proposed method was applied to assay VA in fungal metabolite culture filtrates, and the results were consistent with those obtained by traditional high-performance liquid chromatography. Given that CoO-Co2VO4/C demonstrates both excellent LiP-like and HRP-like activities under different pH conditions, it holds great potential for a wide range of applications.