Extraction and purification of hydrolytic enzymes from activated sludge

► Enzymes can be extracted from activated sludge. ► Ultrasound with a non ionic detergent is able to extract protease and lipase. ► Triton X100 has a strong influence on protease and not on lipase extraction. ► Optimal process was ultrasound, no detergent, plus dialysis and lyophilisation. ► The process allowed recovering up to 23 lipase units/g solid. A major proportion of the organic matter contained by domestic wastewater is mainly formed by lipids, proteins and carbohydrates. Hydrolytic enzymes like proteases and lipases are produced by microorganisms to degrade this organic matter. In the present study protease and lipase were extracted from activated sludge using ultrasound disintegration combined with a non ionic detergent. It was observed that the concentration of Triton X100 has a strong influence for the extraction of protease, while it has a negligible effect for the extraction of lipase. Samples obtained after ultrasound disintegration using 0% and 2% (v/v) Triton X100 were further purified by precipitation with ammonium sulphate and dialysis. The samples were frozen and lyophilised to recover them in powder form. Lipase activity was tested after all the purification steps, finding that the optimal process was a combination of ultrasound treatment (without any detergent) followed by dialysis and lyophilisation. This process allowed recovering up to 23 lipase units/g solid.