Fish processing waste as a source of alkaline proteases for laundry detergent

Proteases were extracted from the viscera of Colossoma macropomum and precipitated with ethanol (30–70%, v/v). The enzymatic extract was partially purified with a yield of 75% (2926 U/g of tissue); at least five caseinolytic proteases bands were observed in zymogram. The optimum pH of the preparation was in the alkaline pH range (10–12). The optimum temperature of activity was 60 °C and only about 15% of the initial activity was lost after an incubation period of 30 min at the above mentioned temperature. Both trypsin and chymotrypsin-like enzymes were detected in the proteases, but with a stronger prevalence for the former. These proteolytic enzymes remained stable in the presence of non-ionic (Tween 20 and Tween 80) and ionic surfactants (saponin and sodium choleate). They also revealed high resistance (60% residual activity) when incubated with 10% H2O2 for 75 min. Furthermore, the preparation retained approximately 80% of its proteolytic activity after incubation for 1 h at 40 °C with the commercial detergent.