Regulation of extracellular laccase production of Agaricus bisporus by nitrogen sources in the medium

Agaricus bisporus was grown on defined liquid media with protein as sole source of carbon, nitrogen or sulphur and with these nutrients supplied in the form of glucose, ammonium or sulphate. Cultures were incubated at 25°C in the dark in static conditions. Mycelia were harvested at suitable intervals, biomass yields determined and culture filtrates tested for extracellular laccase activity. Constitutive laccase production was observed under all conditions tested. However, Agaricus laccase, though constitutive, was induced by protein and repressed by ammonium. No detectable extracellular laccase activity was found in similarly tested cultures of Coprinus cinereus or Volvariella volvacea.