The effect of a lipase-rich enzyme preparation produced by the fungus Penicillium simplicissimum on solid-state fermentation was evaluated in a 4.9 L up-flow anaerobic sludge blanket bioreactor (UASB) treating fish-processing plant wastewater containing 1500 mg oil and grease (O&G)/L The oil and grease hydrolysis step was carried out with 0.5% or 0.2% (w/v) of the solid enzyme preparation (SEP) at 30 degrees C for 8 h. The bioreactor operated at 30 degrees C with a hydraulic retention time of 10 h fora period of over 100 days, showed high total COD removal efficiencies (85.3% for 0.5% SEP and 90.9% for 0.2% SEP), when fed with pre-hydrolyzed wastewater, compared to a Control bioreactor fed with raw wastewater (79.9%). The Control bioreactor also showed high oil and grease accumulation in the biomass throughout the operational period (the O&G content reached 1.7 times that found in the inoculum of the UASB bioreactor), intensive scum formation, and several episodes of cessation of treatment to clean the three-phase separator. Thus it can be concluded that the enzyme pre-hydrolysis step together with anaerobic treatment of the fish-processing plant wastewater improved the quality of the treated effluent and reduced operational problems. (C) 2011 Elsevier Ltd. All rights reserved.