Production, purification and characterization of novel laccase produced by Schizophyllum commune NI_07 with potential for delignification of crop residues

Abstract

The rumen microbial utilization of energy-rich cell walls of crop residues is hindered by the presence of lignin, which limitsits overall digestion process and significantly influences animal performance. In the frame of the development of a bioprocess using the competences of white rot fungi to enhance digestibility of crop residues by delignification, a new strain of Schizophyllum commune NI-07 was isolated. The sole lignolytic activity detected in submerged culture was laccase which increased 3-fold after immobilization of fungus on polyurethane foam cubes. The enzyme was purified 42-fold by employing ammonium sulphate precipitation and size exclusion chromatography on Sephadex G-50 to a specific activity of 15930 U/mg of protein and had a molecular mass of 75 kDa. The laccase obtained from submerged culture medium after cul- tivation of immobilized S. commune NI-07, exhibited considerably higher pH and thermostability and affinity for 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonate) compared to those obtained without immobilization of the fungus. Highly significant (P < 0.05) improvement in the in vitro dry matter digestibility was obtained in 5 common crop residues treated with fungal laccases. We prove the potential of laccase obtained from S. commune NI-07 in enhancement of digestibility of crop residues by way of delignification.