Different inducers for laccase production in Pleurotus ostreatus (ACCC 52857) were screened: carbon and nitrogen source, phenolic compounds and metal ions. Among the tested substances, yeast extract and copper showed the strongest effect on laccase activity. Laccase activity increased during the early phase of cultivation in the presence of yeast extract, peaking on the 6th day and decreasing thereafter. Copper-induced laccase activity increased both in a dose-dependent and a time-dependent manner. The highest laccase activity was obtained with 2 mmol/L Cu 2C , while the mycelial growth was inhibited approximately 27%. Thus, the time-dependent effect of copper on laccase activity was examined. The results showed that the best laccase production was induced when copper was added during the mid-logarithmic phase of cultivation (the 5th day). A positive synergistic effect of yeast extract and copper on the laccase production was observed. Laccase activity dramatically increased upon the addition of copper to medium containing 1% yeast extract on the 5th day of cultivation. The highest activity (8533.33 § 1228.94 U/mL) was observed on the 13th day of cultivation, increased more than 80 folds compared to the original level.

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