Characterization of laccase isoforms produced by Pleurotus ostreatus in solid state fermentation of sugarcane bagasse

► Laccase isoforms pattern and activity were evaluated in solid state fermentation. ► Effects of nitrogen concentration and inducers were tested in sugarcane bagasse. ► Highest laccase activity was achieved with yeast extract 5g/L and both inducers. ► Six laccase isoforms (POXA1b, POXA3, POXC and 3 others) appeared in the native PAGE. ►Mass spectrometry confirmed presence of POXC, POXA3 and 4 other oxidases. Laccases are oxidative enzymes linked to biological degradation of lignin. The aim of this work was to evaluate the effect of inducers and different concentrations of nitrogen on production level of total laccase activity and pattern of laccase isoforms, produced in solid state fermentation of sugarcane bagasse by a selected strain of Pleurotus ostreatus. The addition of yeast extract 5g/L, copper sulfate 150μM and ferulic acid 2mM provided highest enzymatic activity (167U/g) and zymograms indicated the presence of six laccase isoforms (POXA1b, POXA3, POXC and three other isoforms). Results of protein identification by mass spectrometry confirmed the presence of POXC and POXA3 as the main isoenzymes, and also identified a glyoxal oxidase and three galactose oxidases. The fact that the isoenzyme POXA1b was not identified in the analyzed samples can be possibly explained by its sensitivity to protease degradation.