Green technologies for production of oils rich in n-3 polyunsaturated fatty acids from aquatic sources

Microalgae as an emerging alternative raw material of docosahexaenoic acid and eicosapentaenoic acid - a review

Long-chain omega-3 polyunsaturated fatty acids (n-3 PUFAs) have been widely applied due to their nutraceutical and healthcare benefits. With the rising rates of chronic diseases, there is a growing consumer interest and demand for sustainable dietary sources of n-3 PUFAs. Currently, microalgae have emerged as a sustainable source of n-3 PUFAs which are rich in docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA), regarded as promising alternatives to conventional sources (seafood) that cannot meet the growing demands of natural food supplements. This review provides a comprehensive overview of recent advancements in strategies such as genetic engineering, mutagenesis, improving photosynthetic efficiency, nutritional or environmental factors, and cultivation approaches to improve DHA and EPA production efficiency in microalgae cells. Additionally, it explains the application of DHA and EPA-rich microalgae in animal feed, human nutrition- snacks, and supplements to avoid malnutrition and non-communicable diseases.

Effect of four-stage refinement with fortified measures to inhibit oil oxidation and purification on the quality of anchovy oil

Traditional refining processes of crude anchovy oil uses high temperatures. In order to inhibit oil oxidation, intensified measures should be taken. The impact of traditional four-stage refinement on anchovy oil quality have not yet been systematically revealed. This study proposed improved four-stage refining process to refine anchovy oil, and the improved methods could efficiently reduce the risk of oil oxidation. Deacidification could remove some kinds of heavy metal ions but not transition metal ions. Decolorization could remove large amounts of volatile compounds, but it could not effectively improve the sensory quality of oil while deodorization did. The refined efficiency of prior stage greatly influenced that of the latter process. After refinement, purification applying multiple adsorbents could further improve oil quality, but greatly decreased oil oxidation stability. This study provided a reference to the refinement of fish oil and develop progressive refining process inspired by the purification.

Modeling of enzymatic transesterification for omega-3 fatty acids enrichment in fish oil

Mathematical models of transesterification commonly assume that oil is a mixture of triacylglycerols, where each component has only one type of acid attached. This article aims to show how a different assumption on acid distribution affects the results of acylglycerols fraction composition. Experiments of fish oil ethanolysis have been performed at different enzyme loadings and ethanol concentrations, leading to enrichments from 35 % to 52 % of ω3 mass fraction in acylglycerols, by losing 12.1 % of ω3 as ethyl esters. A kinetic model is developed assuming both all acids of the same type on each acylglycerol and all acids randomly distributed on the available positions. The two different assumptions showed strong discrepancies on the acylglycerols fraction compositions predictions, demonstrating how the initial fatty acids distribution is important when an accurate description of the acylglycerols fraction is desired.

Combined cross-linking of Rhizomucor miehei lipase and Candida antarctica lipase B for the effective enrichment of omega-3 fatty acids in fish oil

The incorporation of a non-specific lipase and a sn-1,3 specific one in a single immobilized system can be a promising approach for the exploitation of both lipases. A one-step immobilization platform mediated by an isocyanide-based multi-component reaction was applied to create co-cross-linked enzymes (co-CLEs) of lipases from Rhizomucor miehei (sn-1,3 specific) and Candida antarctica (non-specific). Glutaraldehyde was found to be effective cross-linker by producing specific activity of 16.9 U/mg and immobilization yield of 99 %. High activity recovery of up to 404 % was obtained for immobilized derivatives. Leaking experiment showed covalent nature of the cross-linking processes. BSA had considerable effect on the immobilization process, providing 87-100 % immobilization yields and up to 10 times improvement in the specific activity of the immobilized derivatives. Scanning electron microscopy images showed flower-like and rod-like structures for the CLEs prepared by glutaraldehyde and undecanedicarboxylic acid, respectively. The prepared co-CLEs were examined in non-selective enrichment of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) from fish oil, showing capability of releasing up to 100 % of both omega-3 fatty acids within 8 h of the reaction. The reusability of co-CLEs in five successive cycles presented retaining 63-72 % of their initial activities after the fifth reuse cycle in the hydrolysis reaction.

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

Marine lipids are recognized for their-health promoting features, mainly for being the primary sources of omega-3 fatty acids, and are therefore critical for human nutrition in an age when the global supply for these nutrients is experiencing an unprecedent pressure due to an ever-increasing demand. The seafood industry originates a considerable yield of co-products worldwide that, while already explored for other purposes, remain mostly undervalued as sustainable sources of healthy lipids, often being explored for low-value oil production. These co-products are especially appealing as lipid sources since, besides the well-known nutritional upside of marine animal fat, which is particularly rich in omega-3 polyunsaturated fatty acids, they also have interesting bioactive properties, which may garner them further interest, not only as food, but also for other high-end applications. Besides the added value that these co-products may represent as valuable lipid sources, there is also the obvious ecological upside of reducing seafood industry waste. In this sense, repurposing these bioresources will contribute to a more sustainable use of marine animal food, reducing the strain on already heavily depleted seafood stocks. Therefore, untapping the potential of marine animal co-products as valuable lipid sources aligns with both health and environmental goals by guaranteeing additional sources of healthy lipids and promoting more eco-conscious practices.

Influence of solvent-free extraction of fish oil from catfish (Clarias magur) heads using a Taguchi orthogonal array design: A qualitative and quantitative approach

This study aimed to efficiently utilize catfish heads, enhancing the oil extraction process while improving the cost-effectiveness of fish byproduct management. The study employed the wet rendering method, a solvent-free approach, utilizing a two-factor Taguchi orthogonal array design to identify critical parameters for optimizing oil yield and ensuring high-quality oil attributes. The extraction temperature (80-120°C) and time (5-25 min) were chosen as variables in the wet rendering process. Range analysis identified the extraction time as a more significant (p < 0.05) factor for most parameters, including oil yield, oil recovery, acid value, free fatty acids, peroxide value, and thiobarbituric acid reactive substances. The extraction temperature was more significant (p < 0.05) for oil color. Consequently, the wet rendering method was optimized, resulting in an extraction temperature of 80°C and an extraction time of 25 min, yielding the highest oil yield. This optimized wet rendering process recovered 6.37 g/100 g of oil with an impressive 54.16% oil recovery rate, demonstrating comparable performance to traditional solvent extraction methods. Moreover, Fourier transfer infrared spectra analysis revealed distinct peaks associated with triacylglycerols and polyunsaturated fatty acids (PUFA). The oil recovered under optimized conditions contained higher levels of PUFA, including oleic acid (189.92 μg/g of oil), linoleic acid (169.92 μg/g of oil), eicosapentaenoic acid (17.41 μg/g of oil), and docosahexaenoic acid (20.82 μg/g of oil). Volatile compound analysis revealed lower levels of secondary oxidation compounds under optimized conditions. This optimized wet rendering method offers practical advantages in terms of cost-efficiency, sustainability, reduced environmental impact, and enhanced oil quality, making it an attractive option for the fish processing industries. Future research possibilities may include the purification of the catfish head oil and its application in the food and pharmaceutical industries.

Bioactive fatty acids from non-conventional lipid sources and their potential application in functional food development

There is growing evidence that bioactive fatty acids (BFAs), including eicosapentaenoic acid (EPA; 20:5-3), docosahexaenoic acid (DHA; 22:6-3), and conjugated fatty acids offer multiple biological benefits and constitute ingredients in functional food development. Despite their potential, novel and alternative/nonconventional sources with unique bioactive properties to meet growing demand remain largely unexplored, poorly characterized, and their effects are not well understood. We systematically reviewed the literature to identify studies on alternative sources of BFAs, their functions, extraction, and application in the food and nutraceutical industry. Twenty studies delved into alternate sources such as plants, bacteria, and algae. Six studies found EPA and DHA as the dominant FA in algal sources, while ten studies reported several BFAs from plant sources. Five studies assessed the health benefits of docosapentaenoic acid (DPA), arachidonic acid (ARA), EPA, γ-linolenic acid (GLA), and linoleic acid (LA). Eleven studies compared the quality of oil recovered by green solvents, pressurized liquid, supercritical fluid, and assisted extraction methods. Three studies assessed the effects of assisted extraction methods and reported that these approaches improved oil yield and quality, but the findings may have limited applicability to other lipid sources. The quality of nonconventional lipids largely depends on extraction techniques. Four studies suggested methods like 1D and 2D NMR spectroscopy, LC-MS/MS; however, their analytical differences make accurate comparison inadequate. Five studies found that the incorporation of algal and seafood biolipids during product development increased EHA and DHA contents.

Hyaluronic Acid Poly(glyceryl)10-Stearate Derivatives: Novel Emulsifiers for Improving the Gastrointestinal Stability and Bioaccessibility of Coenzyme Q10 Nanoemulsions

Fish oils are a rich source of polyunsaturated fatty acids, including eicosapentaenoic acid and docosahexaenoic acid, which are reported to exhibit therapeutic effects in a variety of human diseases. However, these oils are highly susceptible to degradation due to oxidation, leading to rancidity and the formation of potentially toxic reaction products. The aim of this study was to synthesize a novel emulsifier (HA-PG10-C18) by esterifying hyaluronic acid with poly(glyceryl)₁₀-stearate (PG10-C18). This emulsifier was then used to formulate nanoemulsion-based delivery systems to co-deliver fish oil and coenzyme Q10 (Q10). Q10-loaded fish oil-in-water nanoemulsions were fabricated, and then their physicochemical properties, digestibility, and bioaccessibility were measured. The results indicated that the environmental stability and antioxidant activity of oil droplets coated with HA-PG10-C18 surpassed those coated with PG10-C18 due to the formation of a denser interfacial layer that blocked metal ions, oxygen, and lipase. Meanwhile, the lipid digestibility and Q10 bioaccessibility of nanoemulsions formulated with HA-PG10-C18 (94.9 and 69.2%) were higher than those formulated with PG10-C18 (86.2 and 57.8%), respectively. These results demonstrated that the novel emulsifier synthesized in this study could be used to protect chemically labile fat-soluble substances from oxidative damage, while still retaining their nutritional value.

Running exercise with and without calcium supplementation from tuna bone reduced bone impairment caused by low calcium intake in young adult rats

Inadequate calcium intake during childhood and adolescence is detrimental to bone metabolism. Here, we postulated that calcium supplement prepared from tuna bone with tuna head oil should benefit for skeletal development than CaCO₃. Forty female 4-week-old rats were divided into calcium-replete diet (0.55% w/w, S1, n = 8) and low-calcium groups (0.15% w/w for 2 weeks; L; n = 32). Then L were subdivided into 4 groups (8/group), i.e., remained on L, L + tuna bone (S2), S2 + tuna head oil + 25(OH)D₃ and S2 + 25(OH)D₃. Bone specimens were collected at week 9. We found that 2 weeks on low calcium diet led to low bone mineral density (BMD), reduced mineral content, and impaired mechanical properties in young growing rats. Intestinal fractional calcium absorption also increased, presumably resulting from higher plasma 1,25(OH)₂D₃ (1.712 ± 0.158 in L vs. 1.214 ± 0.105 nM in S1, P < 0.05). Four-week calcium supplementation from tuna bone further increased calcium absorption efficacy, which later returned to the basal level by week 9. Calcium supplementation successfully restored BMD, bone strength and microstructure. However, 25(OH)D₃ + tuna head oil + tuna bone showed no additive effect. Voluntary running also effectively prevented bone defects. In conclusion, both tuna bone calcium supplementation and exercise are effective interventions for mitigating calcium-deficient bone loss.

Characterization of a New Thermostable and Organic Solution-Tolerant Lipase from Pseudomonas fluorescens and Its Application in the Enrichment of Polyunsaturated Fatty Acids

The search for and characterization of new lipases with excellent properties has always been urgent and is of great importance to meet industrial needs. In this study, a new lipase, lipB, from Pseudomonas fluorescens SBW25, belonging to the lipase subfamily I.3, was cloned and expressed in Bacillus subtilis WB800N. Enzymatic properties studies of recombinant LipB found that it exhibited the highest activity towards p-nitrophenyl caprylate at 40 °C and pH 8.0, retaining 73% of its original activity after incubation at 70 °C for 6 h. In addition, Ca²⁺, Mg²⁺, and Ba²⁺ strongly enhanced the activity of LipB, while Cu²⁺, Zn²⁺, Mn²⁺, and CTAB showed an inhibiting effect. The LipB also displayed noticeable tolerance to organic solvents, especially acetonitrile, isopropanol, acetone, and DMSO. Moreover, LipB was applied to the enrichment of polyunsaturated fatty acids from fish oil. After hydrolyzing for 24 h, it could increase the contents of polyunsaturated fatty acids from 43.16% to 72.18%, consisting of 5.75% eicosapentaenoic acid, 19.57% docosapentaenoic acid, and 46.86% docosahexaenoic acid, respectively. The properties of LipB render it great potential in industrial applications, especially in health food production.

Effect of DHA-Enriched Phospholipids from Fish Roe on Rat Fecal Metabolites: Untargeted Metabolomic Analysis

Lipid metabolism disorder has become an important hidden danger threatening human health, and various supplements to treat lipid metabolism disorder have been studied. Our previous studies have shown that DHA-enriched phospholipids from large yellow croaker (Larimichthys Crocea) roe (LYCRPLs) have lipid-regulating effects. To better explain the effect of LYCRPLs on lipid regulation in rats, the fecal metabolites of rats were analyzed from the level of metabolomics in this study, and GC/MS metabolomics measurements were performed to figure out the effect of LYCRPLs on fecal metabolites in rats. Compared with the control (K) group, 101 metabolites were identified in the model (M) group. There were 54, 47, and 57 metabolites in the low-dose (GA), medium-dose (GB), and high-dose (GC) groups that were significantly different from that of group M, respectively. Eighteen potential biomarkers closely related to lipid metabolism were screened after intervention with different doses of LYCRPLs on rats, which were classified into several metabolic pathways in rats, including pyrimidine metabolism, the citric acid cycle (TCA cycle), the metabolism of L-cysteine, carnitine synthesis, pantothenate and CoA biosynthesis, glycolysis, and bile secretion. L-cysteine was speculated to be a useful biomarker of LYCRPLs acting on rat fecal metabolites. Our findings indicated that LYCRPLs may regulate lipid metabolism disorders in SD rats by activating these metabolic pathways.

Highly Valuable Fish Oil: Formation Process, Enrichment, Subsequent Utilization, and Storage of Eicosapentaenoic Acid Ethyl Esters

In recent years, as the demand for precision nutrition is continuously increasing, scientific studies have shown that high-purity eicosapentaenoic acid ethyl ester (EPA-EE) functions more efficiently than mixed omega-3 polyunsaturated fatty acid preparations in diseases such as hyperlipidemia, heart disease, major depression, and heart disease; therefore, the market demand for EPA-EE is growing by the day. In this paper, we attempt to review EPA-EE from a whole-manufacturing-chain perspective. First, the extraction, refining, and ethanolysis processes (fish oil and ethanol undergo transesterification) of EPA-EE are described, emphasizing the potential of green substitute technologies. Then, the method of EPA enrichment is thoroughly detailed, the pros and cons of different methods are compared, and current developments in monomer production techniques are addressed. Finally, a summary of current advanced strategies for dealing with the low oxidative stability and low bioavailability of EPA-EE is presented. In conclusion, understanding the entire production process of EPA-EE will enable us to govern each step from a macro perspective and accomplish the best use of EPA-EE in a more cost-effective and environmentally friendly way.

The MAP-Kinase HOG1 Controls Cold Adaptation in Rhodosporidium kratochvilovae by Promoting Biosynthesis of Polyunsaturated Fatty Acids and Glycerol

The aim of this study was to investigate the role of RKHog1 in the cold adaptation of Rhodosporidium kratochvilovae strain YM25235 and elucidate the correlation of biosynthesis of polyunsaturated fatty acids (PUFAs) and glycerol with its cold adaptation. The YM25235 strain was subjected to salt, osmotic, and cold stress tolerance analyses. mRNA levels of RKhog1, Δ^12/15-fatty acid desaturase gene (RKD12), RKMsn4, HisK2301, and RKGPD1 in YM25235 were detected by reverse transcription quantitative real-time PCR. The contents of PUFAs, such as linoleic acid (LA) and linolenic acid (ALA) was measured using a gas chromatography-mass spectrometer, followed by determination of the growth rate of YM25235 and its glycerol content at low temperature. The RKHog1 overexpression, knockout, and remediation strains were constructed. Stress resistance analysis showed that overexpression of RKHog1 gene increased the biosynthesis of glycerol and enhanced the tolerance of YM25235 to cold, salt, and osmotic stresses, respectively. Inversely, the knockout of RKHog1 gene decreased the biosynthesis of glycerol and inhibited the tolerance of YM25235 to different stresses. Fatty acid analysis showed that the overexpression of RKHog1 gene in YM25235 significantly increased the content of LA and ALA, but RKHog1 gene knockout YM25235 strain had decreased content of LA and ALA. In addition, the mRNA expression level of RKD12, RKMsn4, RKHisK2301, and RKGPD1 showed an increase at 15 °C after RKHog1 gene overexpression but were unchanged at 30 °C. RKHog1 could regulate the growth adaptability and PUFA content of YM25235 at low temperature and this could be helpful for the cold adaptation of YM25235.

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

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.

Enzyme-Assisted Extraction of Fish Oil from Whole Fish and by-Products of Baltic Herring (Clupea harengus membras)

Baltic herring (Clupea harengus membras) is one of the most abundant commercially caught fish species from the Baltic Sea. Despite the high content of fat and omega-3 fatty acids, the consumption of Baltic herring has decreased dramatically over the last four decades, mostly due to the small sizes and difficulty in processing. At the same time there is an increasing global demand for fish and fish oil rich in omega-3 fatty acids. This study aimed to investigate enzyme-assisted oil extraction as an environmentally friendly process for valorizing the underutilized fish species and by-products to high quality fish oil for human consumption. Three different commercially available proteolytic enzymes (Alcalase^®, Neutrase^® and Protamex^®) and two treatment times (35 and 70 min) were investigated in the extraction of fish oil from whole fish and by-products from filleting of Baltic herring. The oil quality and stability were studied with peroxide- and p-anisidine value analyses, fatty acid analysis with GC-FID, and volatile compounds with HS-SPME-GC-MS. Overall, longer extraction times led to better oil yields but also increased oxidation of the oil. For whole fish, the highest oil yields were from the 70-min extractions with Neutrase and Protamex. Protamex extraction with 35 min resulted in the best fatty acid composition with the highest content of eicosapentaenoic acid (EPA; 20:5n-3) and docosahexaenoic acid (DHA; 22:6n-3) but also increased oxidation compared to treatment with other enzymes. For by-products, the highest oil yield was obtained from the 70-min extraction with Protamex without significant differences in EPA and DHA contents among the oils extracted with different enzymes. Oxidation was lowest in the oil produced with 35-min treatment using Neutrase and Protamex. This study showed the potential of using proteolytic enzymes in the extraction of crude oil from Baltic herring and its by-products. However, further research is needed to optimize enzymatic processing of Baltic herring and its by-products to improve yield and quality of crude oil.

Farmed Gilthead Sea Bream (Sparus aurata) by-Products Valorization: Viscera Oil ω-3 Enrichment by Short-Path Distillation and In Vitro Bioactivity Evaluation

This study shows a pilot scale protocol aimed to obtain an omega 3-enriched oil after the processing of farmed gilthead sea bream viscera (SBV); this was oil was tested in vitro for bioactivity, attesting to the possibility to turn waste into profit The quality of the oil, in terms of requirements for animal and human consumption, was assessed by determining some chemical parameters, such as peroxide value (PV), thiobarbituric acid reactive substances (TBARS), ρ-anisidine (ρ-AV) content, total oxidation value (TOTOX), and phospholipids and free fatty acid (%), both in crude viscera oil (CVO) and refined viscera oil (RVO). Among the extraction conditions, the higher CVO yields were obtained at 60 °C for 10 min (57.89%) and at 80 °C for 10 min (67.5%), and the resulting oxidation levels were low when utilizing both extraction conditions. RVO, obtained from CVO extracted at 60 °C, showed the highest quality on the basis of the assessed parameters. The ethyl esters of the total fatty acid (TFA) contents extracted from RVO were enriched in the ω-3 polyunsaturated fatty acid fraction (PUFAE) up to almost 56% via short path distillation (SPD). Antioxidant activities and adipogenic properties were tested in vitro. PUFAE protected 3T3 L1 cells from oxidative stress and exerted an anti-adipogenic effect in Dicentrarchus labrax pre-adipocytes, attesting to the beneficial properties for both farmed fish and human health. These results could stimulate the adoption of solutions aimed to recover and utilize aquaculture by-products at a higher scale, turning "waste into profit" and indicating a strategy to reach more sustainable business models in aquaculture resource utilization according to the principles of the circular economy.

From Fish Waste to Value: An Overview of the Sustainable Recovery of Omega-3 for Food Supplements

The disposal of food waste is a current and pressing issue, urging novel solutions to implement sustainable waste management practices. Fish leftovers and their processing byproducts represent a significant portion of the original fish, and their disposal has a high environmental and economic impact. The utilization of waste as raw materials for the production of different classes of biofuels and high-value chemicals, a concept known as "biorefinery", is gaining interest in a vision of circular economy and zero waste policies. In this context, an interesting route of valorization is the extraction of omega-3 fatty acids (ω-3 FAs) for nutraceutical application. These fatty acids, such as eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) have received attention over the last decades due to their beneficial effects on human health. Their sustainable production is a key process for matching the increased market demand while reducing the pressure on marine ecosystems and lowering the impact of waste production. The high resale value of the products makes this waste a powerful tool that simultaneously protects the environment and benefits the global economy. This review aims to provide a complete overview of the sustainable exploitation of fish waste to recover ω-3 FAs for food supplement applications, covering composition, storage, and processing of the raw material.