Degradation of lignocellulose by Pleurotus ostreatus in the presence of copper, manganese, lead and zinc

Pleurotus ostreatus produces the cellulolytic and hemicellulolytic enzymes endo-1,4-β-glucanase, exo-1,4-β-glucanase, 1,4-β-glucosidase, endo-1,4-β-xylanase, 1,4-β-xylosidase, endo-1,4-β-mannanase and 1,4-β-mannosidase and ligninolytic enzymes Mn-peroxidase and laccase during growth on wheat straw in the presence and absence of Cu, Mn, Pb, and Zn. This is the first report concerning endo-1,4-β-mannanase in P. ostreatus. Although the concentrations of trace metals in wheat straw ranged from units to tens of μg g−1, only 3-6% (Fe, Pb) or 30-45% (Cu, Mn, Zn) of the total amount was extractable and available for the fungus. The substrate colonization rate was only decreased by high concentrations of Cu and Zn; the loss of dry mass differed among treatments in the initial phase of fungal growth, and at the end of the experiment (day 98) it was significantly lower in metal-containing treatments (63-66%) than in the control (70%). The cellulolytic and hemicellulolytic enzyme were prone to a metal effect except for the increase in endo-1,4-β-glucanase and 1,4-β-glucosidase in the presence of Zn. Laccase activity was increased by all tested metals, and unlike other white-rot fungi, Mn-peroxidase levels were low in the presence of manganese.