Digestive Proteases From Fish Processing Wastes: Their Partial Characterization and Comparison

Fish processing generates a lot of wastes which are discarded resulting in environmental problems. However, this material represents a significant source of high-value bioproducts with potential biotechnological applications. The objective of this study was to characterize and to compare specific activities of acid and alkaline proteases recovered from the viscera of Merluccius hubbsi (Mh), Percophis brasiliensis (Pb), Urophyis brasiliensis (Ub), and Cynoscion guatucupa (Cg) under different pH and temperature conditions. Stomach proteinases from four species had a higher activity at pH 2, with stability in the range of pH 2-4. Optimum pH from intestinal enzymes of Cg was 11.5, while for the crude extract of Mh, Pb, and Ub catalytic activity was registered over a wide pH range range from 7 to 11.5. Stomach proteinases from four studied species had a higher activity at 30 °C and 50 °C, with stability at 10 °C and 30 °C. Optimum temperature from intestinal enzymes of the four tested species was 50 °C with high stability at 10 °C and 30 °C. Alkaline proteinase from all species and acid proteinases from Cg was inactivated at 70ºC, while stomach enzymes of Mh, Pb, and Ub had a residual activity lower than 5% at 80 °C after 5, 10 y 20 minutes of pre-incubation, respectively. Digestive proteinases recovered in this study could be used as biocatalysts in industrial processes, reducing costs, adding value to the fishery waste, and contributing to the reduction of environmental pollution.

Effect of protein extracts of Amaranthus retroflexus (Amaranthaceae) and Cuminum cyminum (Apiaceae) on digestive proteinases and biological characters of Helicoverpa (Heliothis) armigera (Hübner) (Lepidoptera: Noctuidae)

Plant proteinase inhibitors are among the promising biopesticides which are induced in plants tissues against the several Lepidoptera pests to inhibit digestive proteases. In this study, protein extracts of two nonhost plant seeds, Amaranthus retroflexus Linnaeus (Amaranthaceae) and Cuminum cyminum Linnaeus (Apiaceae), were examined on Helicoverpaarmigera (Hübner) (Lepidoptera: Noctuidae). The results obtained by using azocasein as a substrate showed that inhibitory activity of general proteases of the larvae fed on a diet incorporated with both inhibitors was dose dependent. Seed extracts of A. retroflexus and C. cyminum at the highest concentration showed that inhibition activities of chymotrypsin-like proteinase and trypsin-like proteinase were between 31–45% and 28–61%, respectively. Based on polyacrylamide gel electrophoresis, all of the proteinase isoforms, including those of A. retroflexus seed extracts, disappeared entirely, and only one band was detected in the seed extracts of C. cyminum. Larval mortality in the larvae fed on A. retroflexus and C. cyminum seed extracts was 56 ± 2.15 and 68 ± 2.23, respectively, but mortality in control (no seed protein extract) was 12 ± 2.34 individuals. Also, the life table parameters were affected significantly by A. retroflexus and C. cyminum protein seed extracts. Therefore, A. retroflexus and C. cyminum seed protein extracts showed inhibitory effect on H. armigera digestive proteinases and adverse effects on survival and fitness of the pest; hence, they could be introduced as a successful biopesticide in the near future.