Delignification of Lignocellulose Biomasses by Alginate–Chitosan Immobilized Laccase Produced from Trametes versicolor IBL-04

Abstract

An extracellular laccase was produced from a lignin-degrading white-rot fungus Trametes versicolor IBL-04 using the solid-state bioprocessing of corncobs. The enzyme thus produced was effectively immobilized on alginate–chitosan beads. Immobilized laccase furnished the highest immobilization yield (81.43 ± 2.98) under optimized working conditions of 3.0% (w/v) sodium alginate concentration, 2.4% CaCl2, 0.25% chitosan concentration following an immobilization time of 5 h. The immobilization process altered the optimum pH from 5.0 to 4.0 (an acidic shift), whereas the temperature optima were displaced from 40 to 50 °C (towards higher temperature). The Michaelis–Menten constant (K m) and the maximum reaction rate (V max) of the free and immobilized laccase were 0.14 mM, and 780 µmol/mL and 0.10 mM and 814 µmol/mL, respectively. The alginate–chitosan immobilized laccase was more stable and tolerant against the activity inhibition caused by the denaturants tested, concerning its soluble laccase. Delignification results revealed that the enzyme led to a marked reduction in lignin content of all the lignocellulosic wastes with the highest delignification of 78.29% in sugarcane bagasse, followed by wheat bran and corn stover after 15 h. It is demonstrated that the immobilized laccase could be a promising option as a green catalyst for the efficient delignification of lignocellulosic biomass residues.