Aquaculture By-products Research Articles

Fisheries and aquaculture by-products: Case studies in Norway, United States, and Vietnam

Fishmeal and fish oil (FMFO) have historically come from capture fisheries, although supply from capture fisheries is constrained and demand for FMFO is increasing. Fish production losses and by-products are an alternative raw material for FMFO, however, there is little systematic data collected on the use of these raw materials and limited knowledge about barriers to their use in FMFO production. This study collected data on production losses and by-products from seven fisheries and aquaculture sectors that are important in supplying the US seafood market. From 2019–2021, quantitative surveys (n=47 businesses), semi-structured qualitative interviews (n=31 businesses), and secondary data were collected for the study period of 2014–2018. There was significant variation in utilization of production losses and by-products across sectors (range: 37–99 %), and overall, the aggregate utilization rate was 72 %. Scale appeared to be the most important factor leading to use of production losses and by-products. Aquaculture industries in this study had a large and relatively steady supply of by-products year-round, which made investments in FMFO plants worthwhile and led to moderate to high rates of by-product utilization. Wild-caught fisheries in this study had lower rendering rates due to short fishing seasons, smaller scales, operations in remote locations, and regulations that allow dumping of by-products. There were several examples of companies that invested in rendering plants because it was profitable to sell the rendered waste, while other sectors and industries require better coordination and policy supports to make use of this valuable resource.

The use of fishery and aquaculture by-products with Nannochloropsis sp. allows total dietary replacement of wild-caught fishmeal, fish oil and soy protein in European sea bass juveniles

Five experimental diets (CTRL, 50FMFO, 50FMFO-50MIC, 0FMFO-50MIC, 0FMFO-100MIC) were formulated to replace wild-caught fishmeal (FM), wild-caught fish oil (FO) and soy protein using fisheries, aquaculture by-products (BP) and microalgae (MIC). Fifty European sea bass juveniles were distributed in 15 tanks (initial body weight 46.66 ± 0.04 g) and reared in a recirculating aquaculture system for 88 days. Temperature, salinity, oxygen and photoperiod were kept constant throughout the experiment (22 ± 0.5 °C, 25 g L−1 and 8.0 ± 1.0 mg L−1, 12:12 light/dark, respectively). Growth, feed intake (FI), proximal composition, nutritional index, apparent digestibility, somatometric indexes, blood plasma biochemistry and digestive enzyme activity were evaluated. Also, gut microbiota composition was assessed through next-generation sequencing. Results showed that growth performance and feed digestibility were not affected by FM, FO and soy replacement using BP and MIC. Dietary replacement of 100% FM and FO with circular substitutes and 50% replacement of soymeal with microalgae increased the activity of alkaline phosphatase and chymotrypsin. Moreover, the inclusion of BP and MIC had positive effects on the gut microbiota richness and abundance. In conclusion, the utilization of BP and MIC represents a valuable alternative to FM and FO as well as soy protein in feed for European sea bass juveniles.

Bioconversion of Shrimp Waste into Functional Lipid by a New Oleaginous Sakaguchia sp.

Chitin, the second most abundant biomolecule after cellulose in nature, is a significant aquaculture by-product, and is estimated at 6-8 million tons annually. Chitin is composed of monomeric N-acetylglucosamine (NAG) which can be seen as an alternative feedstock for biotechnology. Microbial functional lipids have gained attention due to their bioactivity and sustainable production. In this study, a new oleaginous yeast strain named Sakaguchia sp. HKC2 was found to be able to use NAG as the carbon source for growth and accumulate functional lipids such as PUFAs and carotenoids. When cultured on the NAG-containing medium, strain HKC2 exhibited slower growth and slower intracellular lipid accumulation compared to those on a glucose-containing medium. However, the lipids obtained from HKC2 grown on NAG medium were richer in PUFAs. Notably, torularhodin-a powerful bioactive carotenoid-was found in all HKC2 cultures on NAG, while torulene was abundant in glucose medium. These findings highlight a novel avenue for utilizing aquatic by-products and unlocking their potential.

Adsorption efficiency of biochar produced by aquaculture by-products for removing geosmin in aquaculture environment

Abstract Aquaculture produces numerous by-products like aquatic plants, algae, and nutrient-enriched sediment annually, which are often discarded as waste, are not environmentally friendly, and are harmful to the environment. In this study, aquaculture by-products were utilized to prepare moss biochar at 500, 700, and 800 °C (BC500, BC700, and BC800, respectively); Elodea biochar (WBC800) at 800 °C; and sediment biochar (SBC800) at 800 °C. Characterization and experimental results showed that BC800 had the best adsorption effect on geosmin (GSM) under the same conditions; when using BC800 to treat GSM solution with a pH of 7, the adsorption efficiency of GSM was high (97.08%) under the conditions of dosage of 1.0 g, temperature of 25 °C, and adsorption time of 2 min. Adsorption is a multimolecular layer process that involves both physical aspects of porous adsorption and connections between chemical bonds. Biochar, derived from aquaculture by-products, is utilized to eliminate odorous substances in aquaculture environments, thereby promoting resource recycling.

Experimental study on environment-friendly concrete production incorporating palm oil clinker and cockle shell powder as cement partial replacement

The demand for civil construction has increased recently; cement is now the most produced and consumed material globally. The carbon dioxide (CO2) emissions are strongly influenced by the cement industry which make up 5 to 7% total global emissions, are ejaculating at a rate of one ton of CO2 for every ton of cement produced. Consequently, additional cementitious substances like palm oil clinker powder (POCP), a by-product of palm oil mills and cockle shell powder (CSP), an agricultural and aquaculture byproduct derived from cockle shell combustion, can beemployed as partially binding materialto alleviate the ecologicalfootprint of cement manufacturing. By substituting cement in different weight ratios ranging from 0 to 20%, this study examines the impacts of POCP and CSP on concrete. Concrete compressive strength, flexural strength and water absorption of varying POCP and CSP proportions for 7 and 28 days of curing are analyzed in the experimental investigation. Thisresearch demonstrated that samples with 10% cement substitution, comprising 5% POCP and 5% CSP, performed well in terms of mechanical aspects and water absorption. The study of concrete structures with POCP and CSP is a novel and important scientific topic, according to the research findings, and it should be emphasized.

Fisheries and aquaculture by-products modulate growth, body composition, and omega-3 polyunsaturated fatty acid content in black soldier fly (Hermetia illucens) larvae

The black soldier fly (BSF) (Hermetia illucens L.) is one of the most promising species for the production of ingredients, mainly protein, useful for animal feed formulation, owing to its ability to convert organic waste into biomass with a high nutritional value. However, the low percentage of n-3 series polyunsaturated fatty acids (PUFAs) in its fatty acid profile is a limiting factor for the utilization of BSF in fish feed. Recent studies have highlighted that wastes derived from different agro-food value chains could affect the nutritional composition of BSF larvae, depending on the composition of the wastes used as larvae-growing substrate. Due to the significant amount of n-3 PUFA in marine products, both in edible produce and in by-products, in this study, different sources of fish by-products were included in experimental diets for BSF to evaluate the effect of its addition on the final nutritional profile of BSF pre-pupae. One control diet and five experimental diets were prepared to feed the BSF larvae: wheat bran as the control diet (diet B), bycatch from Mediterranean trawl fisheries (diet F), Parapenaeus longirostris processing by-products (diet S), aquaculture processing by-products (diet R), Thunnus albacares processing by-products (diet T), and Engraulis encrasicolus processing by-products (diet A). In this study, the effects of the different diets were analyzed on the growth, body composition, and fatty acid profile of BSF larvae and pre-pupae. The obtained results showed that the different experimental diets affected total lipids content and fatty acids composition, when compared with the control. A significant increase in eicosapentaenoic (EPA) and docosahexaenoic acid (DHA) in BSF larvae and pre-pupae fed with all fish by-products was observed when compared with those fed with diet B, in particular in larvae and pre-pupae fed with diet A, demonstrating that the utilization of fish processing by-products is a suitable solution for improving the nutritional value of insects as ingredients in aqua feeds. The reuse of marine by-products can contribute to the industry’s “zero waste” goal, increasing the sustainability of the fishery value chain and the formulation of new valuable products.

Towards a free wild-caught fishmeal, fish oil and soy protein in European sea bass diet using by-products from fishery and aquaculture

One of the main strategies to implement the sustainability of aquaculture is by reducing its dependence on feed raw materials derived from wild marine resources, unsustainable land and freshwater use. To totally replace wild-caught fishmeal (FM), fish oil (FO) and soy protein (SP) in European sea bass, five experimental diets were formulated including increasing levels of fishery and aquaculture by-products (control C, 0FM100FO, 0FM0FO, 0FM0FO-50SP, 0FM0FO-0SP). Diets were administered to triplicate fish groups of 50 individuals reared in a recirculation system for 119 days. No major differences (p > 0.05) between C and 0FM100FO were detected in growth (final body weight) and feed efficiency parameters (feed conversion rate, protein efficiency ratio, gross protein efficiency, lipid efficiency ratio, gross lipid efficiency) while they were reduced (p < 0.05) in 0FM0FO, 0FM0FO-50SP, 0FM0FO-0SP compared to C diet. At the end of the growth trial the overall metabolomic profiles of fish muscle were impacted by the diets. In particular, the increase in glycine and phosphocreatine in the muscle of fish fed with diets containing FM and FO by-products, may suggest changes or adaptation in metabolic pattern for energy production at muscular level; results which were also supported by the higher level in plasma creatinine, uric acid and lactate found in C diets. Concerning welfare indicators, overall plasma parameters were in line with the normal range for this species indicating a general optimal welfare condition under all dietary regimes. No effect of diets on overall gut microbiota layout was observed. However, the inclusion of the FM and FO by-product increase the relative abundance of several taxa such as Weissela, Enterococcus, Streptococcus and Bacillus which could potentially support immune system and disease resistance. Overall this study highlighted the possibility of totally replacing wild-caught FM and FO using by-products from fisheries and aquaculture with an only marginal reduction of the overall performance.

Perspectives for Exploitation of Sabella spallanzanii’s Biomass as a New Integrated Multi-Trophic Aquaculture (IMTA) By-Product: Feeding Trial on Amphiprion ocellaris Using Sabella Meal

This paper is part of a series of studies aimed at understanding the potential exploitation of the biomass of the polychaete worm Sabella spallanzanii (Gmelin, 1791), which is obtained as a by-product of an innovative Integrated Multi-Trophic Aquaculture (IMTA) system. IMTA systems are designed according to an ecosystem approach with the aim to reduce marine monoculture impact while further increasing production via exploitation of valuable by-products. S. spallanzanii can remove large amounts of suspended matter by filtering large volumes of water per hour and performs well as an extractive organism under IMTA; however, it currently lacks any economic value, thus hindering its sustainable large-scale implementation. However, S. spallazanii has the potential to become competitive as a newcomer in fish bait, as an ornamental organism, and in fish feed markets. Notably, sabella meal has already been successfully tested as an attractant in an innovative fish feed. Here, we refer to the use of sabella meal as the main component (60%) in the formulation of a novel aquarium fish feed. Following the biochemical analysis of farmed sabella meal, the experimental feed was formulated by adding spirulina (25%) and dry garlic (15%) in such proportion as to be isoproteic and isoenergetic to the commercial control feed. After preliminary observations of the palatability of sabella meal for several tropical fish species, the novel experimental feed was tested on ocellaris clownfish, Amphiprion ocellaris (Cuvier, 1830), by evaluating their growth response in a 70-day feeding trial. The fish seemed to enjoy the experimental feed at least as much as the control, and both the control and treatment groups showed no significant differences in weight gain (p = 0.46), specific growth rate (p = 0.76), and feed conversion ratio (p = 0.48), reinforcing the suitability of S. spallanzanii as a viable source of animal proteins to be employed in the fish feed industry in a circular economy perspective.

Marine Sources of DHA-Rich Phospholipids with Anti-Alzheimer Effect.

Alzheimer's disease (AD) is a complex and progressive disease, which affects millions of people around the world. Despite the many efforts over the years to find efficient therapeutics, there is no cure yet. Nonetheless, many compounds have been proven to decrease Alzheimer's symptoms. After a short overview of the hypotheses considered in AD drug development and the drugs approved for AD treatment, which lead to symptom release, we focus on the valorization of natural marine sources that decrease AD symptoms, particularly on docosahexaenoic acid (DHA), an important component in membrane phospholipids and the most abundant n-3 polyunsaturated fatty acids (PUFA) found in gray matter of the brain and in retina and on the DHA-containing phospholipids (DHA-PLs) present in marine sources, namely fish, krill, mollusks and in fisheries and aquaculture by-products. DHA-PLs' bioactivities are presented, namely their properties in anti-neurodegeneration, neuroinflammation, as anticancer agents, as well as their benefits to obesity and visual problems. Fisheries and aquaculture by-products are also highlighted as they have a high content of DHA and DHA-rich phospholipids, can be extracted by green methodologies and should be considered in a circular economy for a healthy sustainable future.

Removal of Heavy Metals from Acid Mine Drainage with Lab-Scale Constructed Wetlands Filled with Oyster Shells

The present study investigated the applicability of constructed wetlands (CWs) filled with oyster shells (OSs) for removing heavy metals from acid mine drainage (AMD). Lab-scale CWs consisted of columns (ID 12.5 cm, H 50 cm) packed with OSs or limestone, which were left unplanted or planted with cattails. Synthetic and real AMD containing 7.3 mg/L of Zn, 38.0 mg/L of Fe, and other minerals (pH = 4.0) were fed to the CWs (1 L/column) under a hydraulic retention time of 7 days in a sequencing batch mode. The effluent pH values of the CWs reached 6.9–8.3. Results show that OSs with high CaCO3 contents had higher neutralizing capability for AMD than limestone had. During 7 months of operation, all CWs were highly effective for removing Zn (88.6–99.2%); Fe (98.7–99.7%); and Cd, Cu, Pb, As, and Mn (48.2–98.9%) from both real and synthetic AMD. The mass balance in the CWs indicated accumulation in OSs or limestone as a main pathway for removing heavy metals, representing 44.8–99.3% of all metals, followed by biomass (8.8–29.9%) in the planted CWs. Other processes examined for this study only played a minor role in removing heavy metals. The higher metal treatment performance of OS CWs demonstrated the value of this aquaculture byproduct as a CW substrate.

Adult European Seabass (Dicentrarchus labrax) Perform Well on Alternative Circular-Economy-Driven Feed Formulations

There is an increasing need in the aquaculture industry for more sustainable and functional feed concepts for marine finfish. This study provides results for the effect of alternative feed formulations on health status, welfare parameters, sensory analysis, and growth performance in European seabass (Dicentrarchus labrax) over an 83-day feeding trial. Fish were fed twice a day with five experimental diets. A control diet (control) and four different alternative feed concepts rich in processed animal proteins (PAP), other alternative ingredients (NOPAP), and a positive (NOPAP+) and negative (PAP−) formulation were tested. All alternative formulations contained hydrolysates from aquaculture by-products and macroalgae. The results indicate that the alternative feed concepts are more sustainable alternatives compared with the commercial diet. Equally interesting, the alternative formulations did not affect the sensory analysis of the fillet quality or the animal welfare. These are increasingly important factors in aquaculture products and, accordingly, also in the formulation of new feeds. Feed concepts that are not only more sustainable in their production, have shorter transportation distances, recycle the resources (usage of by-products), and have no adverse effect on growth or welfare parameters are highly needed. Therefore, the experimental diets tested in this study are a win-win concept for future seabass aquaculture production.

A novel fish meal-free diet formulation supports proper growth and does not impair intestinal parasite susceptibility in gilthead sea bream (Sparus aurata) with a reshape of gut microbiota and tissue-specific gene expression patterns

The exponential growth of the aquaculture sector requires the development of sustainable aquafeeds with less dependence on marine products. The maximized replacement of fish meal (FM) and fish oil (FO) with plant ingredients has been extensively studied in the economically important species gilthead sea bream (Sparus aurata). Recently, major progress has been done with other alternative raw materials, though some non-pathological inflammatory response persisted with feed formulations that increased the circularity of resource utilization. In the present study, we evaluated the effects on growth performance, gene expression, intestinal microbiota and disease resistance of a FM-free diet (NoPAP SANA), based on plant ingredients, aquaculture by-products, algae oil, insect meal and bacterial fermentation biomasses as main dietary oil and protein sources, and supplemented with a commercially available health-promoting feed additive (SANACORE®GM). Juveniles of 21 g initial body weight were fed control or NoPAP SANA diets for 34 days, and head kidney, liver and posterior intestine were collected for gene expression analyses using customized PCR-arrays. Each tissue-specific PCR covered 96 genes in total and included markers of growth performance, lipid and energy metabolism, antioxidant defence, immune system, and intestinal function and integrity. From the same fish, the adherent bacteria of the posterior intestine were studied by Illumina sequencing of the V3-V4 region of the 16S rRNA. The remaining fish were challenged with the intestinal parasite Enteromyxum leei for 78 days and sampled for parasite diagnosis. Both control and NoPAP SANA fish grew efficiently considering gilthead sea bream standards. Before parasite challenge, the NoPAP SANA group showed differential expression of 17, 2 and 4 genes in liver, head kidney and posterior intestine, respectively. The intestinal bacterial composition showed no major differences in diversity or at the phylum level. However, 29 abundant OTUs significantly changed with the diet. From these, 10 OTUs were significantly correlated with differentially expressed genes in the different target tissues. Inferred metagenome analyses revealed that the altered microbiota with NoPAP SANA diet could account for changes in 15 metabolic pathways. The intensity and prevalence of infection after the parasite challenge did not significantly vary between dietary treatments, and infected fish from both groups showed similar disease outcome. Altogether, these results indicate that the NoPAP SANA diet promoted optimal growth and a healthy condition in gilthead sea bream without affecting susceptibility against the tested intestinal parasite, as often observed with alternative diets following current industry formulations.

Dietary effects of a low-molecular weight fraction (

Aquaculture by-products have been of great interest for producing protein hydrolysates with multiple biological activities. The present experiment was carried out to evaluate dietary effects of a low-molecular fraction (<10 kDa) from shrimp waste hydrolysate in forms of unprotected and nanocapsulated on growth and immunity of rainbow trout. Therefore, six diets were designed including a control diet (no supplementation), D1 (1 g kg−1 of unprotected fraction), D2 (1 g kg−1 chitosan nanocapsules), D3 (1 g kg−1 liposome nanocapsules), D4 (1 g kg−1 of fraction-loaded chitosan nanocapsules), D5 (1 g kg−1 of fraction-loaded liposome nanocapsules). Fish (0.91 ± 0.15 g) were fed with experimental diets until apparent satiation for six weeks followed by a 5-day experimental challenge with Streptococcus iniae. Results revealed that growth is strongly affected in fish receiving the fraction with D4 treatment showing the highest weight gain, SGR, final weight and the lowest FCR (p < 0.05). Nanocapsules without fraction did not show remarkable effects when compared to control group. In terms of serum and mucus immune parameters of lysozyme, complement activity, myeloperoxidase activity, and total protease, fish from D4 group showed the highest measured values followed by D5 (p < 0.05). Key immune related genes of IL-6 and TNF-α were noticeably up-regulated in fish from D1, D4, and D5 groups, which were consistent with survival rate after 5 days challenge with Streptococcus iniae. All together, the present findings highlighted the application of chitosan and liposome nanocarriers in aquaculture and potential of low-molecular weight fraction (<10 kDa) from shrimp wastes hydrolysate to improve growth performance and immune status of rainbow trout.

A potential flavor seasoning from aquaculture by-products: An example of Takifugu obscurus

There is a growing interest in the value utilization of fish by-products. In this study, an advisable method of Takifugu obscurus by-products hydrolysates (F0) developed into flavor seasoning was investigated. The F0 were separated into two peptide fractions, >3000 Da (F1) and 300–3000 Da (F2), and performed Maillard reaction, then flavor characteristics of the Maillard reaction products were comprehensively analyzed. The results showed that the Maillard reaction largely improved flavor profiles of the hydrolysates i.e., enhancing umami taste, volatile aroma, and overall acceptance, while reducing bitterness and fishy smell. Compared with F0 and F1, F2 as the suitable resource of flavor precursors, had the optimal flavor attributes after Maillard reaction. This paper provides a new idea of comprehensive utilization of by-products of pufferfish and guides the preparation of Maillard peptide-based seasoning from fish by-products.

Bioactive Compounds of Nutraceutical Value from Fishery and Aquaculture Discards.

Seafood by-products, produced by a range of different organisms, such as fishes, shellfishes, squids, and bivalves, are usually discarded as wastes, despite their possible use for innovative formulations of functional foods. Considering that “wastes” of industrial processing represent up to 75% of the whole organisms, the loss of profit may be coupled with the loss of ecological sustainability, due to the scarce recycling of natural resources. Fish head, viscera, skin, bones, scales, as well as exoskeletons, pens, ink, and clam shells can be considered as useful wastes, in various weight percentages, according to the considered species and taxa. Besides several protein sources, still underexploited, the most interesting applications of fisheries and aquaculture by-products are foreseen in the biotechnological field. In fact, by-products obtained from marine sources may supply bioactive molecules, such as collagen, peptides, polyunsaturated fatty acids, antioxidant compounds, and chitin, as well as catalysts in biodiesel synthesis. In addition, those sources can be processed via chemical procedures, enzymatic and fermentation technologies, and chemical modifications, to obtain compounds with antioxidant, anti-microbial, anti-cancer, anti-hypertensive, anti-diabetic, and anti-coagulant effects. Here, we review the main discards from fishery and aquaculture practices and analyse several bioactive compounds isolated from seafood by-products. In particular, we focus on the possible valorisation of seafood and their by-products, which represent a source of biomolecules, useful for the sustainable production of high-value nutraceutical compounds in our circular economy era.

Biotechnological Valorization of Food Marine Wastes: Microbial Productions on Peptones Obtained from Aquaculture By-Products.

Based on a biotechnological strategy, in the present work several peptones are produced from the Alcalase hydrolysis (0.1–0.2% v/w, 56–64 °C, pH 8.27–8.98, 3 h) and thermal processing (105 °C, 60 min) of wastes generated from the industrial processing of turbot, salmon, trout, seabream and seabass. These peptones were included (in the range of 2.6–11 g/L of soluble protein) as main source of organic nitrogen (protein substrates) in low-cost media for the culture of lactic acid bacteria (LAB), marine probiotic bacteria (MPB) and ubiquitous Gram+ bacteria. In most cases, batch fermentations conducted in aquaculture peptone media led to the best growth, metabolic productions and yields. Nevertheless, no significant differences between aquaculture peptones and commercial media were generally observed. Kinetic parameters from a logistic equation and used for cultures modeling were applied with the purpose of comparing the bioproduction outcomes. In economical terms, the validity of the aquaculture peptones as substitutives of the peptones (meat extract, casitone, etc.) from commercial media was also compared. The decreasing of the costs for LAB bioproductions ranged between 3–4 times and the growth costs of MPB and Gram+ bacteria were improved more than 70 and 15 times, respectively, in relation to those found in control commercial media.

수산양식 부산물을 이용한 퇴적물 개선 및 효율 평가

This study was carried out to evaluate aquaculture by-products, abalone and oyster shell, as sediment amendments and compare their efficiency with those of commercially available products. It was revealed that four remediation materials could effectively lower the COD and AVS of organically enriched sediment mainly by dilution effect. Moreover, remediation materials made of abalone or oyster shell showed as similar remediation efficiency as compared with commercial amendments. It also suggested that in order to reduce COD and AVS to the level of 90% of original concentration, any of four remediation materials could be applied with the amount of 10~40 kg to square meter of organically enriched sediments.

Nutritional Profiling and the Value of Processing By-Products from Gilthead Sea Bream (Sparus aurata).

Fish processing industries generate a large volume of discards. In order to fulfil with the principles of a sustainable circular economy, it is necessary to maintain aquaculture by-products in the food chain through the production of high-value biomolecules that can be used as novel ingredients. In this study, we try to give value to the gilthead sea bream by-products, evaluating the composition and the nutritional value of the muscle and six discards commonly obtained from the fish processing industry (fishbone, gills, guts, heads, liver, and skin), which represent ≈ 61% of the whole fish. Significant differences were detected among muscle and by-products for fatty acid and amino acid profile, as well as mineral content. The discards studied were rich in protein (10%–25%), showing skin and fishbone to have the highest contents. The amino acid profile reflected the high quality of its protein, with 41%–49% being essential amino acids—lysine, leucine, and arginine were the most abundant amino acids. Guts, liver, and skin were the fattiest by-products (25%–35%). High contents of polyunsaturated fatty acids (PUFAs) (31%–34%), n-3 fatty acids (12%–14%), and eicosapentaenoic acid (EPA) + docosahexaenoic acid (DHA) (6%–8%) characterized these discards. The head displayed by far the highest ash content (9.14%), which was reflected in the mineral content, especially in calcium and phosphorous. These results revealed that gilthead sea bream by-products can be used as source of value-added products such as protein, oils, and mineral supplements.

Valorization of Aquaculture By-Products of Salmonids to Produce Enzymatic Hydrolysates: Process Optimization, Chemical Characterization and Evaluation of Bioactives.

In the present manuscript, various by-products (heads, trimmings, and frames) generated from salmonids (rainbow trout and salmon) processing were evaluated as substrates for the production of fish protein hydrolysates (FPHs), potentially adequate as protein ingredients of aquaculture feeds. Initially, enzymatic conditions of hydrolysis were optimized using second order rotatable designs and multivariable statistical analysis. The optimal conditions for the Alcalase hydrolysis of heads were 0.1% (v/w) of enzyme concentration, pH 8.27, 56.2°C, ratio (Solid:Liquid = 1:1), 3 h of hydrolysis, and agitation of 200 rpm for rainbow trout and 0.2% (v/w) of enzyme, pH 8.98, 64.2 °C, 200 rpm, 3 h of hydrolysis, and S:L = 1:1 for salmon. These conditions obtained at 100 mL-reactor scale were then validated at 5L-reactor scale. The hydrolytic capacity of Alcalase and the protein quality of FPHs were excellent in terms of digestion of wastes (Vdig > 84%), high degrees of hydrolysis (Hm > 30%), high concentration of soluble protein (Prs > 48 g/L), good balance of amino acids, and almost full in vitro digestibility (Dig > 93%). Fish oils were recovered from wastes jointly with FPHs and bioactive properties of hydrolysates (antioxidant and antihypertensive) were also determined. The salmon FPHs from trimmings + frames (TF) showed the higher protein content in comparison to the rest of FPHs from salmonids. Average molecular weights of salmonid-FPHs ranged from 1.4 to 2.0 kDa and the peptide sizes distribution indicated that hydrolysates of rainbow trout heads and salmon TF led to the highest percentages of small peptides (0–500 Da).

Integrated Multitrophic Aquaculture By-Products with Added Value: The Polychaete Sabella spallanzanii and the Seaweed Chaetomorpha linum as Potential Dietary Ingredients.

Aquaculture expansion is limited by the negative environmental impact of the waste and the need for alternative sources in the diet of reared fish. In this framework, for the first time, the survival rates, biomass gain, and fatty acid profiles of the polychaete Sabella spallanzanii and the macroalga Chaetomorpha linum, reared/cultivated as bioremediators in an integrated multitrophic aquaculture system (IMTA), were evaluated for their potential reuse applications. Results showed that these organisms represent a natural source of omega-3 and omega-6. On account of the overall results and the high biomass obtained as by-products, a preliminary study was performed employing both S. spallanzanii and C. linum as new dietary ingredients to feed different sized Dicentrarchus labrax. Fish survival rate, biomass growth, and specific growth rate were determined resulting in no significant differences between control and treated fishes. Histological analyses showed no alterations of the stomach tunica mucosa and submucosa in treated fishes. The eco-friendly approaches applied in the here-realized IMTA system could guarantee the achievement of sustainable by-products represented by the bioremediators S. spallanzanii and C. linum, as well as their reliability as a natural source of compounds beneficial to fish and human health.