Background: Although laccase has a good catalytic oxidation ability, free laccase shows a poor stability. Enzyme immobilization is a common method to improve enzyme stability and endow the enzyme with reusability. Adsorption is the simplest and common method. Modified biochar has attracted great attention due to its excellent performance.
Results: In this paper, cetyltrimethylammonium bromide (CTAB)-KOH modified biochar (CKMB) was used to immobilize laccase by adsorption method ([email protected]). Based on the results of the single-factor experiments, the optimal loading conditions of [email protected] were studied with the assistance of Design-Expert 12 and response surface methods. The predicted optimal experimental conditions were laccase dosage 1.78 mg/mL, pH 3.1 and 312 K. Under these conditions, the activity recovery of [email protected] was the highest, reaching 61.78 %. Then, the CKMB and [email protected] were characterized by TGA, FT-IR, XRD, BET and SEM, and the results showed that laccase could be well immobilized on CKMB, the maximum enzyme loading could reach 57.5 mg/g. Compared to free laccase, the storage and pH stability of [email protected] was improved greatly. The [email protected] retained about 40 % of relative activity (4 ℃, 30 days) and more than 50 % of relative activity at pH 2-6. In addition, the [email protected] indicated the reusability up to 6 reaction cycles while retaining 45.1 % of relative activity. Moreover, the thermal deactivation kinetic studies of [email protected] showed a lower k value (0.00275 min-1) and higher t1/2 values (252.0 min) than the k value (0.00573 min-1) and t1/2 values (121.0 min) of free laccase.
Conclusions: We explored scientific and reasonable immobilization conditions of [email protected], and the [email protected] possessed relatively better stabilities, which gave the immobilization of laccase on this cheap and easily available carrier material the possibility of industrial applications.