From waste to profit: high biological value marine products, for the valorization and recovery of fisheries, aquaculture and fish processing by-products for the improvement of the sustainability of the supply chain

The increasing demand for fish products, both for food and non-food purposes, is raising serious concerns for the environmental sustainability of fish production, that is affected by multiple factors as fisheries management, economic competition, and inadequate management of wastes. To address these challenges, the European Green Deal and Sustainable Development Goal 14 of the 2030 Agenda ("Life Below Water") prioritizes the sustainability of the blue economy and the fisheries sector also by the valorization of by-products from fisheries, aquaculture, and fish processing, that represents an effective solution to promote circular blue economy. My PhD project focused on the valorization of Sicilian fish by-products to contribute to the “zero waste” goal, with the aim to improve the value chain and supporting the achievement of the Sustainable Development Goals, for the recovery of bioactive components of high biological value and their application in other industrial sectors.The thesis is divided into three parts, in accord with the development of application of bioactive compounds in different industrial sectors: nutraceutical, feed and food. The part one is related to the valorization of marine by-products in the nutraceutical sector, starting from the side streams from the fisheries and aquaculture value chains, in order to evaluate the possibility of producing tuna oil (TO) as a valuable source of n-3 polyunsaturated fatty acids (PUFA), (Chapter 1). Fish oil is one of the main bioactive components that can be extracted from fish by-products and represents the most important natural source of the essential polyunsaturated fatty acids (PUFAs), of the n-3 series, such as eicosapentaenoic acid (EPA, 20:5n-3) and docosahexaenoic acid (DHA, 22:6n-3). These essential fatty acids are used both in feed for aquaculture and as oil or food supplement capsules for direct human consumption. In this study, side streams produced during filleting fattened bluefin tuna (Thunnus thynnus) were collected and analyzed for proximate composition and fatty acid profile to evaluate the possibility to produce tuna oil (TO) by set-up procedure for enrichment in n-3 PUFA.The procedure short path distillation (SPD) was set-up and to almost 85% of the PUFA fraction (PUFA-SPe) was enriched. The bioactivity of all the fractions of oils was tested in vitro for lipid metabolism, in gilthead sea bream (Sparus aurata) fibroblast cell line (SAF-1). TFA and PUFA-SPd upregulated transcription factors (pparβ and pparγ) and lipid metabolism-related genes (D6D, fas, fabp, fatp1, and cd36), indicating the promotion of adipogenesis. PUFA-SPe treated cells were similar to control. The results indicate that PUFA-SPe modulates fat deposition, contributing to improve health and the quality of its products. (Chapter 1 - Published chapter: Messina, Arena et al. 2022).The second part of the thesis is related to the valorization of marine by-products in the aquafeed sector, by focusing its potential use in the modulation of the nutritional profile of one the most studied organism in the past decade for this purpose: the insect Hermetia illucens. The use of insects as source of ingredients for aquaculture is highlighted by hundreds of research and papers produced on this subjects.In this study, by-catch collected from the Mediterranean trawler fishing species, Parapenaeus longirostris processing by-products, aquaculture by-products (from sea bass and sea bream filleting), Thunnus albacares processing by-products, and Engraulis encrasicolus by-products (heads and viscera) were used and incorporated in experimental diets for black soldier fly (BSF) (H. illucens L.) to evaluate the effect of their inclusion on the final nutritional profile of BSF larvae (Chapter 2). The BSF is one of the most promising species for industrial production and animal feed in the world, due to its ability to bioconvert various organic substrates (animal and plant origin) into larval biomass within a 14-day period under optimal growth conditions (temperature of 27°C and humidity of 70%).In recent years, the use of insect meal, mainly as an alternative source of proteins in fishmeal, has also increased in the aquaculture sector. Nevertheless, only a limited number of studies have explored the potential of using BSF as a source of fatty acids due to the low content of n-3 series PUFAs, such as EPA and DHA, which are essential for fish. Recent research has shown that the fatty acid composition of BSF larvae can be modified by utilizing different feed substrates, thereby adding value. The use of marine by-products generated from a diverse supply chain would provide an opportunity to enrich BSF larvae with essential PUFA. The incorporation of marine by-products as feed for BSF would not only reduce food waste but also result in the production of high-quality larvae. The findings of this study demonstrate that the diverse experimental diets not only influenced the nutrient composition but also the fatty acid profile. A significantly higher n-3 fatty acid content was observed in the fatty acid profile of BSF pre-pupae fed different fish by-products compared to the control. In particular, the pre-pupae that were fed a diet containing by-products of E. encrasicolus exhibited the highest levels of EPA, followed by the pre-pupae that were fed diets containing by-products of T. albacares, by-catch from Mediterranean trawlers, and aquaculture by-products.The observed results of this study corroborate the hypothesis that the utilization of marine sources, particularly fish by-products, can improve the nutritional profile of BSF larvae and pre-pupae by providing essential fatty acids, such as EPA and DHA, which are not naturally present in BSF.This approach not only demonstrates the possibility of incorporating n-3 components into insects, but also highlights the potential of using these insects as a valuable ingredient in aquatic feeds. Furthermore, this method promotes circular economy pathways at the regional level, in line with the objectives of the European Green Deal (Chapter 2 - Published chapter: Arena et al., 2023).The third part of the thesis reports the valorization of marine by-products in the food sector, specifically in the fish processing industry. During my PhD, I had the opportunity to work with the company Blu Ocean s.r.l., the industrial partner of the project, was initiated. This company, which has been active in fish processing for almost a century, stands out for its expertise in the sector and its commitment to sustainability and product quality.In collaboration with Blu Ocean, it was possible to identify some strategies to reduce waste along the supply chain, with the idea to turn residues into useful resources. Recently, in response to the emergency caused by the blue crab invasion, Blu Ocean has initiated preliminary activities to promote this species by producing new food products. However, the large amount of waste generated requires the implementation of innovative solutions for its valorization. Given the expertise in the lab on extraction of bioactive compound I studied the composition of the blue crabs by products, focusing on the production of protein hydrolysates.Blue Crab (Callinectes sapidus), native to the western Atlantic Ocean, has recently spread to the Mediterranean Sea, where it is considered one of the 100 most invasive species. This opportunistic species is known for its adaptability to different temperatures and salinities but has a negative impact on biodiversity and human activities, such as fishery and tourism. Despite these negative effects, the blue crab is attracting increasing interest as a food resource due to its high nutritional value. Blue crab meat is rich in protein (14% to 30%) and omega-3 fatty acids (EPA and DHA). The use of this species in the production of new foods could not only mitigate the impact of its invasiveness, but also create new economic opportunities (Chapter 3). One of the most significant challenges related to this potential resource is the management of waste. The global production of crab shells is estimated to be between 6 and 8 million tons per year. This has the potential to create significant issues surrounding disposal and environmental sustainability.The low economic value of crab shells often results in their disposal in landfills, highlighting the need for more sustainable solutions. It is imperative that these residues be valorized in order to enhance economic and environmental sustainability. Crab shells and other by-products contain a range of valuable components, including proteins, lipids, chitin, minerals, and pigments, which can be processed into high-value products. While the valorization of crustacean by-products has been widely studied, there is a paucity of research specifically focused on the blue crab (C. sapidus). However, studies have indicated that blue crab by-products have the potential to be utilized in various sectors, thereby reducing environmental impact, promoting a circular economy, and creating new industrial opportunities (Chapter 3 Published chapter: Arena et al., 2024).Given the lack of information on the use of protein hydrolysates derived from the by-products of the blue crab (C. sapidus), in vitro tests were carried out on these hydrolysates to assess their potential, in order to help local businesses to recover and valorize the by-products of this species according to the principles of the circular economy (Chapter 4).This study first evaluated the yield of blue crab meat, showing that, as indicated in the literature, the yield from processing this crab is very low, resulting in considerable waste, much of which remains underutilized. Blue crab by-products (BCBP) were analyzed to determine their proximate composition, which revealed a high protein content, justifying the study on the valorization of this component. Specially, protein hydrolysates were produced from BCBPs by enzymatic hydrolysis, an environmentally friendly technique that allows the production of protein hydrolysates of high nutritional value. In the present study, the hydrolysates were obtained using the enzymes Alcalase and Protamex and subsequently tested for their antioxidant activity using the DPPH assay and human fibroblast cell (HS-68) tests. The results showed that the Alcalase enzyme was more effective than Protamex. It achieved a degree of hydrolysis (DH%) of over 20%. This suggests that the resulting hydrolysates may be suitable for utilization as food additives. The two enzymes exhibited high proteolytic activity, as evidenced by SDS-PAGE electrophoresis. The protein hydrolysates derived from the blue crab by-products exhibited notable antioxidant properties, displaying considerable DPPH radical scavenging capacity and moderate reducing power. Furthermore, the hydrolysates demonstrated enhanced viability in HS-68 cells when compared to untreated cells that had been subjected to stress. These results indicate that high-quality bioactive compounds derived from blue crab by-products may have significant applications in the food, nutraceutical, and pharmacological sectors. In particular, for example, they could be incorporated into chitosan-gelatin films as antioxidant food additives, thus producing active food packaging with antioxidant properties.This study demonstrates how this species can be transformed from a problematic by-product to a valuable resource. (Chapter4).During my research project I had possibility to evaluate the potential of the production of by-products from fisheries, aquaculture, and fish processing. The studies carried out identified some strategies to valorize these by-products by extracting bioactive components useful in areas such as nutraceuticals, animal feed and human nutrition. The achieved results are in line with the objectives and provided basis for further applications and developments in the field of marine biobased production.