The efficacy of different Pleurotus ostreatus (L.) isolates to treat pulp and paper industrial effluent on a shake flask and fermentor were studied. In the shake flask and fermentor studies, Pleurotus ostreatus decolorized the effluent 69.68% and 66.66% respectively, on 7TH day of incubation. The chemical oxygen demand was reduced by 61.3% by Pleurotus ostreatus on day 7 of incubation. Various cultural conditions including different glucose concentrations, nitrogen sources, pH, temperature and incubation period influence on biomass and different enzymes viz; xylanase, CMCase and laccase production by Pleurotus ostreatus IMPP-02 were optimized in shake flask cultures. Under these culture conditions, the maximum level of xylanase activity (9.29 Uml-1), CMCase (7.37 U ml-1), laccase (13.57 U ml-1) and effluent decolorization (69.68%) were observed on 7th day during shake flask studies. Furthermore, the optimum pH and temperature were found to be 5.0 and 30 C, respectively in fermentor studies. The maximum color reduction of 66.66 %; biological oxygen demand (BOD) and chemical oxygen demand (COD) reduction of 65.35 % and 61.3 % respectively, were determined during fermentor studies.