Application of laccase immobilized rice straw biochar for anthracene degradation

The present study explores the immobilization of ligninolytic enzyme-laccase on the surface of rice straw biochar and evaluates its application for anthracene biodegradation. The rice straw biochar was acid-treated to generate carboxyl functionality on its surface, followed by detailed morphological and chemical characterization. The surface area of functionalized biochar displayed a two-fold increase compared to the untreated biochar. Laccase was immobilized on functionalized biochar, and an immobilization yield of 66% was obtained. The immobilized enzyme demonstrated operational stability up to six cycles while retaining 40% of the initial activity. Laccase immobilization was further investigated by performing adsorption and kinetic studies, which revealed the highest immobilization concentration of 500 U g(-1) at 25 degrees C. The adsorption followed the Langmuir isotherm model at equilibrium, and the kinetic study confirmed pseudo-second-order kinetics. The equilibrium rate constant (K-2) at 25 degrees C and 4 degrees C were 3.6 x 10(-3) g U-1 min(-1) and 4 x 10(-3) g U-1 min(-1) respectively for 100 U g(-1) of enzyme loading. This immobilized system was applied for anthracene degradation in the aqueous batch mode, which resulted in complete degradation of 50 mg L-1 anthracene within 24 h of interaction exposure. (C) 2020 Elsevier Ltd. All rights reserved.

Automated summary

This study successfully immobilized laccase on the surface of functionalized rice straw biochar, achieving high stability and immobilization yield. Through adsorption and kinetic studies, the optimal immobilization concentration was found at 25 degrees C. The immobilized system was applied for anthracene degradation, resulting in complete degradation within 24 hours.