Effect of different carbon and nitrogen sources on laccase and peroxidases production by selected Pleurotus species

Pleurotus eryngii, P. ostreatus and P. pulmonarius produced laccase (Lac) both under conditions of submerged fermentation (SF) and solid-state fermentation (SSF) with all of the investigated carbon and nitrogen sources. The highest levels of Lac activity were found in P. eryngii, under SF conditions of dry ground mandarine peels and in P. ostreatus, strain No. 493, under SSF conditions of grapevine sawdust. High levels of peroxidases activities were occurred in P. ostreatus, strain No. 494, and P. pulmonarius, under SSF conditions of grapevine sawdust, whereas in SF, these activities were either very low or absent. After purification of extracellular crude enzyme mixture of investigated species and strain which were grown in the medium with the best carbon sources, the Lac activity measurements revealed two peaks in P. eryngii, three peaks in both P. ostreatus strains and three in P. pulmonarius. Results obtained after purification also showed that the levels of phenol red oxidation in absence of external Mn²⁺ were higher than phenol red oxidation levels in presence of external Mn²⁺. In the medium with the best carbon sources (mandarine peels and grapevine sawdust, respectively), both P. eryngii and P. ostreatus, strain No. 493, showed the highest Lac activity with (NH₄)₂SO₄, as a nitrogen source, with a nitrogen concentration of 20 and 30 mM, respectively. In P. ostreatus, strain No. 494, and P. pulmonarius, the best nitrogen sources for peroxidases production were peptone in a concentration of 0.5% and NH₄NO ₃ with a nitrogen concentration of 30 mM, respectively.