Production of enzymatic hydrolysates from blue shark skin by-product using a biorefinery approach

Portugal is the third country in the world with the highest fish consumption, with an average of 59 kg per capita per year. That results in a considerable amount of fish waste, up to 30% of which can be skin and bones. Fish skin mainly comprises collagen (more than 70% of its total protein content). Collagen is a structural protein found in animal extracellular matrices and has a wide range of commercial applications s. In the past, bovine and porcine sources have been the primary sources of collagen, but due to religious beliefs and some infectious diseases, other sources are in debate. Marine-based collagen is an attractive alternative for the industry. Blue shark skin is a by-product of the fishing industry that is rich in collagen. This study used a biorefinery approach to valorize blue shark skin waste. We used a process we reported for another type of marine matrix (cod skin) to obtain collagenic peptide hydrolysates and non-collagenic protein hydrolysates. We evaluated two proteases: alcalase (of microbial origin) and bromelain (of vegetable origin). We performed a multifactorial optimization study for both matrices and both enzymes, considering as responses the degree of hydrolysis and antioxidant activity for all models and, additionally, protein solubilization for the case of collagen hydrolysates. In all cases, alcalase was the enzyme with the best performance. Once we validated the predictive models, we chose the most viable conditions, and the production of these hydrolysates was scaled up to pilot production. The optimized hydrolysates present molecular profiles, bioactivities, and organoleptic characteristics of interest for the nutraceutical and cosmetic industries (in the case of collagen hydrolysates) and aquaculture (in the case of non-collagen hydrolysates). In conclusion, this study has demonstrated that blue shark skin waste can be valorized to produce collagenic peptide hydrolysates and non-collagenic protein hydrolysates, which have potential applications in the nutraceutical, cosmetic, and aquaculture industries.