Digestive proteinases from marine fish processing wastes of Southwest Atlantic Ocean: their partial characterization and comparison

Abstract

Fish processing generates plenty of waste that is directly discarded on open-air dumpsand water sources, or treated in the same way as urban solid waste causing seriouspollution problems. The waste represents a significant source of high-value bioproductswith potential applications in different industrial processes such as the production of feed,fertilizers, biodiesel and biogas, detergent additives and cosmetics. The objective of thisstudy was to characterize and to compare specific activities under different pH values andtemperature conditions of acid and alkaline proteinases and viscera yield from thefollowing fish species: Argentine hake Merluccius hubbsi, Brazilian flathead Percophisbrasiliensis, Brazilian codling Urophycis brasiliensis, and Stripped weakfish Cynoscionguatucupa. Individuals were fished off the coast of Mar del Plata (Argentina) by acommercial fleet and the viscera were immediately extracted and kept on ice until use.Stomach proteinases from four species had the highest activity at pH 2, with stability inthe range of pH 2-4. The optimum pH was 11.5 from intestinal enzymes of C. guatucupa,M. hubbsi and P. brasiliensis and 9.5 from intestinal enzymes of U. brasiliensis. Alkalineproteinases from all species were highly stable in the range of 7-11.5. The optimumtemperature of stomach proteinases from the four species studied were 30 °C and 50 °C,with stability at 10 °C and 30 °C during 150 min. The optimum temperature of intestinalenzymes from the tested species were 50 °C with high stability at 10 °C and 30 °C during150 min. Alkaline proteinase from all species and acid proteinases from C. guatucupawere inactive at 70 ºC after 150 min; while there was a residual activity lower than 5 %at 80 °C on pre-incubated stomach enzymes of M.hubbsi, P. brasiliensis and U.brasiliensis after 5, 10 and 20 minutes, respectively. Digestive proteinases recovered inthis study could be appropriate for technological usage, reducing manufacturing costs,obtaining revenue from fishery wastes, and contributing to the reduction of environmental pollution.