Contribution of protein hydrolysates and brain lipids to the integral valorization of blue shark (Prionace glauca) waste

Processing of blue shark generates a variety of polluting residues, being heads the most prominent. Previous valorization efforts have extracted chondroitin sulfate, apatites, and hyaluronate from blue shark heads, but brain and muscle tissue remain after these processes. The present study aims at completing the integral valorization of blue shark heads by investigating the valorization of these remaining fractions to approach a zero-waste objective. In the first case, the dominant lipid classes extracted from the brain comparing three extraction protocols reveal a rich composition of ceramide-type sphingolipids, glycerophospholipids and neutral lipids, with potential for use in the cosmetic and pharmaceutical industries. Secondly, comparison of papain and alcalase for the enzymatic hydrolysis of the remaining muscle tissue along with water resulting from cooking heads, point to alcalase as the best option, achieving a high degree of hydrolysis at 1:1 solid to liquid ratio, 55°C, pH 8.2, 0.1% (w/v) of alcalase, and 3 h of hydrolysis. These hydrolysates, incorporated as peptones in the formulation of low-cost nutrient media, successfully support the growth of probiotic lactic acid bacteria and marine bacteria, demonstrating their suitability as a sustainable nitrogen source for biotechnological applications. These findings highlight the potential for significantly reducing waste and increasing the sustainability of the blue shark fishing industry by utilizing previously discarded fractions.