Valorization of Side Stream Products from Sea Cage Fattened Bluefin Tuna (Thunnus thynnus): Production and In Vitro Bioactivity Evaluation of Enriched ω-3 Polyunsaturated Fatty Acids

Abstract

The valorization of side streams from fishery and aquaculture value-chains is a valuable solution to address one of the challenges of the circular economy: turning wastes into profit. Side streams produced after filleting of sea cage fattened bluefin tuna (Thunnus thynnus) were analyzed for proximate composition and fatty acid profile to evaluate the possibility of producing tuna oil (TO) as a valuable source of ω-3 polyunsaturated fatty acids (PUFA) and testing its bioactivity in vitro. Ethyl esters of total fatty acids (TFA), obtained from TO, were pre-enriched by urea complexation (PUFA-Ue) and then enriched by short path distillation (SPD) up to almost 85% of the PUFA fraction (PUFA-SPe). The bioactivity of TFA, PUFA-SPe, and ethyl esters of depleted PUFA (PUFA-SPd) were tested in vitro, through analysis of lipid metabolism genes, in gilthead sea bream (Sparus aurata) fibroblast cell line (SAF-1) exposed to oils. 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. PUFA-SPe extracted from farmed bluefin tuna side streams could be utilized in fish feed formulations to prevent excessive fat deposition, contributing to improving both the sustainability of aquaculture and the quality of its products.

Marine Animal Co-Products—How Improving Their Use as Rich Sources of Health-Promoting Lipids Can Foster Sustainability

“…A summary of the beneficial health effects ascribed to the lipids present in marine animal co-products is presented in Figure 4. The lipid content in marine animal co-products, although not predominant, is still very substantial, especially, as described before, in certain fish and shellfish species (it can represent more than 25% of co-products of meagre (A. regius) [94], sea bass (D. labrax) [93,95], Chinook salmon (O. tshawytscha) [103], gilthead sea bream (S. aurata) [91,94], sardinelle (S. aurita) [97], salmon (S. salar) [93], or bluefin thuna (T. thynnus) [96]), crustaceans (it can amount to more than 10% DW in shrimp co-products of Argentine red shrimp (P. muelleri) [55] or whiteleg shrimp (P. vannamei) [132,133] and to more than 15% in some lobsters, namely Australian lobster (P. cygnus) [126] and Australian rock lobster (J. edwardsii) [127]) and mollusks (more than 10% in Patagonian squid (D. gahi) [68,150], Argentine shortfin squid (I. argentinus) [151], giant squid (D. gigas) [119], or common octopus (O. vulgaris) [67] co-products). Obviously, the higher the lipid content, the more justifiable it is to explore and take advantage of these co-product matrixes as possible sources of healthy lipids.…”

“…Lipid content in the co-products of aquaculture bluefin tuna (T. thynnus) was reported to represent up to 32.1% [96], while lipid content in the viscera of sardinelle (Sardinella aurita) was shown to vary seasonally, attaining a maximum yield of 25.4% (DW) [97]. However, other marine animal co-products were reported to display lower but still considerable lipid levels, such as the viscera of yellowfin tuna (T. albacares), containing 5.1% fat [98], the viscera of Atlantic herring (Clupea harengus), containing 9.6% lipids [99], or the viscera of salema (Sarpa salpa), displaying a maximum of 3.6% lipids [97].…”

“…Among fish co-products, those from marbled rockcod (Notothenia rossii, >30% omega-3 fatty acids [110]), blue mackerel (S. australasicus, >35% [104]), and Atlantic bluefin tuna (T. thynnus, 29.9% [96]), the viscera of sardinelle (S. aurita, 26.1% [97]), and the co-products of Atlantic herring (C. harengus, 26.5% [109]) are especially good potential omega-3 sources. In crustaceans, the exoskeletons of southern king crab (L. santolla, 40% [55]), exoskeletons and heads of Argentine red shrimp (P. muelleri, >40% [55]), processing co-products of northern shrimp (P. borealis, 37.1% [59]), and the cephalothorax of the Norway lobster (N. norvegicus, 27.6% omega-3 fatty acids) [61] present the highest percentages of omega-3.…”

“…The repurposing of marine animal co-products aligns with eco-intensification paradigms and can promote a lower Fish In: Fish Out (FIFO) ratio [283]. In fact, oils produced from marine animal co-products (e.g., tuna fish side streams) have been ascribed beneficial effects when used in formulations, preventing excessive fat deposition in farmed fish [96]. Also, products based on processed side streams of shrimp and crab are already being used in animal feeds to balance their nutrient profiles [284].…”