Circular valorisation of fish processing by-products: integrated protease recovery and functional protein hydrolysate production

The fishing industry’s increasing production on a global scale has led to significant waste generation, posing environmental concerns and opportunities for valorisation. This review explores the potential of fish processing by-products as a source of valuable biomaterials, emphasising the interconnected roles of proteases and protein hydrolysates in transforming waste into high-value products. The use of endogenous proteases from fish viscera and commercial enzymes is effective in producing bioactive peptides with a variety of suitable applications in functional foods, nutraceuticals, and pharmaceutical products. The production of fish protein hydrolysates (FPH) via enzymatic hydrolysis has become a viable method for repurposing protein-rich waste products, as FPH demonstrates significant nutritional benefits, bioactive peptides, and uses in the food and aquaculture industries. The review also delves deeper into the classification, anatomical sources, and recovery of endogenous proteases from fish by-products, highlighting their potential as a cost-effective and sustainable alternative to commercial enzymes. Alternative purification methods, such as aqueous two-phase systems (ATPS) and three-phase partitioning (TPP), are efficient and cost-effective for recovering and purifying proteases from fish waste, offering advantages over conventional methods. The applications of fish proteases in various industries, including food, detergent, leather, pharmaceutical, and aquafeed, are also discussed, emphasising the importance of purity levels for different applications. In conclusion, fish waste valorisation has the potential to contribute to environmental protection, food security, and sustainable bio-based material production. Future studies should focus on optimising hydrolysis process variables, exploring the use of stable and naturally derived enzyme preparations, and conducting extensive in vivo testing to support health-related claims. Collaboration between stakeholders, including researchers, industry actors, and policymakers, is essential for achieving a shift from a linear “catch-processing-discarding” system to a circular system, which in turn will promote a more sustainable and eco-friendly fishing industry.