Production of lignocellulolytic enzymes by Trametes gallica and detection of polysaccharide hydrolase and laccase activities in polyacrylamide gels

Abstract

White rot fungus Trametes gallica was studied for the production of lignocellulolytic enzymes: cellulase, xylanase, laccase, manganese-dependent peroxidase (MnP), and lignin peroxidase (LiP). The results demonstrated that low-nitrogen (2.2 mM N) and surface stationary cultivation favored production of extracellular MnP. MnP activity reached 118.1 UL(-1) while T. gallica was grown in a low-nitrogen culture containing phenylalanine. However, laccase levels observed in high-nitrogen (22 mM N) agitated cultures were much greater than those seen in low-nitrogen. The N source experiments seemed to reveal that NH4+ plays an important role in inducing MnP and laccase of the fungus. Results showed that T. gallica produces a series of the lignocellulolytic enzymes, and needs high N to produce all the enzymes during solid-state fermentation of wheat straw. This paper also presents a modified zymogram procedure to detect xylanase and laccase of T. gallica in polyacrylamide gel. Xylanase in crude enzyme of T. gallica was displayed by contacting protein gel strips with xylan substrate gels and by staining with iodine. By immersing the protein gel strips in o-tolidine solution, the blue-green zones representing laccase activity were visualized against a colorless background.