The effect of carbon and nitrogen sources, lignocellulosic substrates, and metal ions on lignin peroxidase (UP) activity of Aspergillus sp., which was isolated from a mangrove area, was studied. Glucose (1%) was found to be the best carbon source. Among the various lignocellulosic substrates used, coir pith at 3% concentration increased UP activity twofold on the second day of incubation. Peptone and KNO3, completely inhibited the enzyme synthesis while (NH4)(2)SO4 at 12.5 mM produced maximum activity. Since sea-water contained all the requisite metal ions, any added ions had a negative effect on activity. Cu2+ had the most inhibiting effect while K+ the least. When all the optimized conditions were provided, in nitrogen- and carbon-sufficient medium, a maximum UP activity of 345 U/mL, was obtained on the second day of incubation.