BIO-GENAGE GLOBAL FOUNDATION

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Protein and peptides: This is the most diversified and highly valued group of seafood by-products, with applications in most industrial areas. It includes bioactive peptides (antioxidant and antihypertensive), collagen and gelatin, enzymes, peptones, and protein extracts. In addition to traditional uses in enzymatic reactions or as medicines, there are also novel and disruptive applications of these ocean biomolecules. For example, phycobiliproteins from red algae can be used to produce photovoltaic cells to capture low light underwater.138 Regarding the most common protein and peptide-based products, they include:

(a) Bioactive peptides (antioxidant and antihypertensive) – Usually extracted from the liver and viscera of fish and are mainly applied as medicines.97

(b) Collagen and gelatin – Obtained by thermal denaturation of collagen, they are proteins with applications in pharmaceutical, biomedical, leather, cosmetics, and tissue-engineering industries due to their unique structural and functional features. The fish skins, scales, and fins are rich in collagen, but it is also present in the meat and viscera of fish.75,112–116

(c) Enzymes – Different classes of enzymes can be found on the viscera of fish and marine invertebrates, particularly digestive enzymes such as carbohydrases,97 proteases (e.g., chymotrypsin, pepsin, and trypsin),99,100,119–121 lipases, and phospholipases.97,100 Other enzymes include lipoxygenase, myosin ATPases, polyphenol oxidases, transglutaminases.99,100,119–121 Most enzymes extracted from seafood are used for medical and industrial applications, but lipases and phospholipases are also employed by the food, chemical, and biofuel industries.97,100

(d) Peptones – Peptones are semi-digested proteins that are used as a carbon and nitrogen source. They can be extracted from fish and marine invertebrates waste and used to produce animal feed, chemicals, and nutraceuticals.84

(e) Protein extracts – Seafood is a rich source of animal protein. Protein extracts can be obtained from algae, fish, and invertebrate animal waste. They can be used as food additives, nutraceuticals, chemicals, pharmaceuticals, animal feed, and fertilizers.63,75

To better elucidate the sources and applications of different seafood waste products, a schematic representation associating each product and its respective source(s) and application(s) is presented in Fig. 5.