Catalytic and Operational Stability of Acidic Proteases from Monterey Sardine (Sardinops sagax caerulea) Immobilized on a Partially Deacetylated Chitin Support

Recovery of valuable compounds from by-products generated from seafood processing represents an opportunity to produce value-added products. Sardine acidic proteases were immobilized on partially deacetylated chitin through ionic linkages, using sodium tripolyphosphate as a support activating agent. Maximal enzyme activities of free and immobilized proteases were detected at pH 2, at which the immobilized form had higher stability than the free enzymes. Optimum temperatures for free and immobilized proteases were 40 and 50C, respectively, while thermal stability of immobilized proteases was greater than that of free proteases. Reusability studies showed that after a second catalytic cycle, the immobilized enzyme maintained about 40% of the initial activity. The immobilization process enhanced the long term storage stability of sardine proteases compared to free enzymes. Results suggest that the immobilized enzyme could be used as a biotechnological aid for food processing when low pH and temperature around 50C are needed. Practical Applications: Fish waste constitutes a serious environmental problem due to high disposal costs. Besides, this waste is commonly discarded or used for low value processes. Therefore, this study proposes the immobilization of sardine (Sardinops sagax caerulea) acidic proteases from fish viscera waste, on a partially deacetylated chitin support extracted from shrimp (Penaeus spp.) head. This research suggests that seafood protease immobilization onto chitinous supports presents an opportunity to improve the stability of these enzymes and consequently enhance potential application of these valuable biocatalysts as biotechnological aid, mainly for food processing and other value added products.