Sustainability is a key principle in natural resource management, and it involves operational efficiency, minimisation of environmental impact and socio-economic considerations; all of which are interdependent. It has become increasingly obvious that continued reliance on fossil fuel energy resources is unsustainable, owing to both depleting world reserves and the green house gas emissions associated with their use. Therefore, there are vigorous research initiatives aimed at developing alternative renewable and potentially carbon neutral solid, liquid and gaseous biofuels as alternative energy resources. However, alternate energy resources akin to first generation biofuels derived from terrestrial crops such as sugarcane, sugar beet, maize and rapeseed place an enormous strain on world food markets, contribute to water shortages and precipitate the destruction of the world's forests. Second generation biofuels derived from lignocellulosic agriculture and forest residues and from non-food crop feedstocks address some of the above problems; however there is concern over competing land use or required land use changes. Therefore, based on current knowledge and technology projections, third generation biofuels specifically derived from microalgae are considered to be a technically viable alternative energy resource that is devoid of the major drawbacks associated with first and second generation biofuels. Microalgae are photosynthetic microorganisms with simple growing requirements (light, sugars, CO 2 , N, P, and K) that can produce lipids, proteins and carbohydrates in large amounts over short periods of time. These products can be processed into both biofuels and valuable co-products. This study reviewed the technologies underpinning microalgae-to-biofuels systems, focusing on the biomass production, harvesting, conversion technologies, and the extraction of useful co-products. It also reviewed the synergistic coupling of microalgae propagation with carbon sequestration and wastewater treatment potential for mitigation of environmental impacts associated with energy conversion and utilisation. It was found that, whereas there are outstanding issues related to photosynthetic efficiencies and biomass output, microalgae-derived biofuels could progressively substitute a significant proportion of the fossil fuels required to meet the growing energy demand.

/pdf/biofuels-from-microalgae-a-review-of-technologies-for-1t1wwr5e69.pdf

Biofuels from microalgae—A review of technologies for production, processing, and extractions of biofuels and co-products

Unsustainable fishing practices have placed a heavy emphasis on aquaculture to meet the global shortfalls in the supply of fish and seafood, which are commonly accepted as the primary source of health-promoting essential omega-3 (n-3 highly unsaturated fatty acids). However, dietary fish oil is required for the production of omega-3-rich farmed fish and this commodity, in a vicious circle, is at present derived solely from wild fisheries. Decreasing global availability coupled with the highly variable price of this resource has forced the aquaculture industry to investigate the possibilities of alternative dietary lipid sources. This review attempts to compile all principal information available regarding the effects of fish oil replacement for the diets of farmed finfish, analysing the findings using a comparative approach among different cultured fish species. The review initially focuses on the present situation with regard to the production, availability and main nutritional characteristics of fish oil and the principal alternative lipid sources (such as vegetable oils and animal fats). Following this, the effects of fish oil replacement in finfish nutrition on feed quality, fish performance, feed efficiency, fish lipid metabolism, final eating quality and related economic aspects are presented and discussed.

Fish oil replacement in finfish nutrition

Essential fatty acid (EFA) requirements vary qualitatively and quantitatively with both species and during ontogeny of fish, with early developmental stages and broodstock being critical periods. Environment and/or trophic level are major factors, with freshwater/diadromous species generally requiring C18 polyunsaturated fatty acids (PUFA) whereas marine fish have a strict requirement for long-chain PUFA, eicosapentaenoic, docosahexaenoic and arachidonic acids. Other than marine fish larvae, defining precise quantitative or semi-quantitative EFA requirements in fish have received less attention in recent years. However, the changes to feed formulations being forced upon the aquaculture industry by the pressing need for sustainable development, namely the replacement of marine fish meal and oils with plant-derived products, have reintroduced EFA into the research agenda. It is particularly important to note that the physiological requirements of the fish to prevent deficiency pathologies and produce optimal growth may not parallel the requirements for maintaining nutritional quality. For instance, salmonids can be successfully cultured on vegetable oils devoid of long-chain n-3 PUFA but not without potentially compromising their health benefits to the human consumer. Solving this problem will require detailed knowledge of the biochemical and molecular basis of EFA requirements and metabolism.

Fatty acid requirements in ontogeny of marine and freshwater fish

Growing consumer interest in grass-fed beef products has raised a number of questions with regard to the perceived differences in nutritional quality between grass-fed and grain-fed cattle. Research spanning three decades suggests that grass-based diets can significantly improve the fatty acid (FA) composition and antioxidant content of beef, albeit with variable impacts on overall palatability. Grass-based diets have been shown to enhance total conjugated linoleic acid (CLA) (C18:2) isomers, trans vaccenic acid (TVA) (C18:1 t11), a precursor to CLA, and omega-3 (n-3) FAs on a g/g fat basis. While the overall concentration of total SFAs is not different between feeding regimens, grass-finished beef tends toward a higher proportion of cholesterol neutral stearic FA (C18:0), and less cholesterol-elevating SFAs such as myristic (C14:0) and palmitic (C16:0) FAs. Several studies suggest that grass-based diets elevate precursors for Vitamin A and E, as well as cancer fighting antioxidants such as glutathione (GT) and superoxide dismutase (SOD) activity as compared to grain-fed contemporaries. Fat conscious consumers will also prefer the overall lower fat content of a grass-fed beef product. However, consumers should be aware that the differences in FA content will also give grass-fed beef a distinct grass flavor and unique cooking qualities that should be considered when making the transition from grain-fed beef. In addition, the fat from grass-finished beef may have a yellowish appearance from the elevated carotenoid content (precursor to Vitamin A). It is also noted that grain-fed beef consumers may achieve similar intakes of both n-3 and CLA through the consumption of higher fat grain-fed portions.

/pdf/a-review-of-fatty-acid-profiles-and-antioxidant-content-in-56v8grm3id.pdf

A review of fatty acid profiles and antioxidant content in grass-fed and grain-fed beef

https://www.dur-a-avaler.com/wp-content/uploads/2013/02/Red%20meat%20consumption%20An%20overview%20of%20the%20risks%20and%20benefits.pdf

Red meat consumption: an overview of the risks and benefits.

The UK dietary guidelines for cardiovascular disease acknowledge the importance of long-chain omega-3 polyunsaturated fatty acids (PUFA) - a component of fish oils - in reducing heart disease risk. At the time, it was recommended that the average n-3 PUFA intake should be increased from 0.1 to 0.2 g day(-1). However, since the publication of these guidelines, a plethora of evidence relating to the beneficial effects of n-3 PUFAs, in areas other than heart disease, has emerged. The majority of intervention studies, which found associations between various conditions and the intake of fish oils or their derivatives, used n-3 intakes well above the 0.2 g day(-1) recommended by Committee on Medical Aspects of Food Policy (COMA). Furthermore, in 2004, the Food Standards Agency changed its advice on oil-rich fish creating a discrepancy between the levels of n-3 PUFA implied by the new advice and the 1994 COMA guideline. This review will examine published evidence from observational and intervention studies relating to the health effects of n-3 PUFAs, and discuss whether the current UK recommendation for long-chain n-3 PUFA needs to be revisited.

https://www.csuchico.edu/grassfedbeef/research/documents/sources/Ruxton%20Omega3%20review.pdf

The health benefits of omega-3 polyunsaturated fatty acids: a review of the evidence

The UK dietary guidelines for cardiovascular disease acknowledge the importance of long-chain omega-3 polyunsaturated fatty acids (PUFA) - a component of fish oils - in reducing heart disease risk. At the time, it was recommended that the average n-3 PUFA intake should be increased from 0.1 to 0.2 g day -1 . However, since the publication of these guidelines, a plethora of evidence relating to the beneficial effects of n-3 PUFAs, in areas other than heart disease, has emerged. The majority of intervention studies, which found associations between various conditions and the intake of fish oils or their derivatives, used n-3 intakes well above the 0.2 g day -1 recommended by Committee on Medical Aspects of Food Policy (COMA). Furthermore, in 2004, the Food Standards Agency changed its advice on oil-rich fish creating a discrepancy between the levels of n-3 PUFA implied by the new advice and the 1994 COMA guideline. This review will examine published evidence from observational and intervention studies relating to the health effects of n-3 PUFAs, and discuss whether the current UK recommendation for long-chain n-3 PUFA needs to be revisited.

The health benefits of omega-3 polyunsaturated fatty acids: a review of the evidence. Commentary

A considerable literature has been published on the health benefits of fish, oil-rich fish and fish oils and their constituent long-chain (LC) n-3 PUFA. Evidence from epidemiological studies highlights the cardioprotective attributes of diets rich in fish, especially oil-rich fish. Data from intervention trials are consistent in suggesting that LC n-3 PUFA lower the risk of CVD, probably by the multiple mechanisms of lowering serum triacylglycerols, improving the LDL:HDL ratio, anti-arrhythmic effects on heart muscle, improved plaque stability, anti-thrombotic effects and reduced endothelial activation. Research indicates LC n-3 PUFA provision has an impact during development, and there is preliminary evidence that docosahexaenoic acid supplementation during pregnancy could optimise brain and retina development in the infant. LC n-3 PUFA are also postulated to ameliorate behavioural and mental health disturbances such as depression, schizophrenia, dementia and attention deficit hyperactivity disorder. However, despite some positive evidence in each of these areas, use of LC n-3 PUFA in these conditions remains at the experimental stage. In the case of immune function, there is little doubt that LC n-3 PUFA have a positive effect. Although intervention trials in rheumatoid arthritis show strong evidence of benefit, evidence for efficacy in other inflammatory conditions, including Crohn's disease, ulcerative colitis, psoriasis, lupus, multiple sclerosis, cystic fibrosis and asthma, is inconsistent or inadequate. More promising evidence in some conditions may come from studies which attempt to modify the fetal environment using LC n-3 PUFA supplementation during pregnancy.

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S. C. Reed

Papers

The health benefits of omega-3 polyunsaturated fatty acids: a review of the evidence

The health benefits of omega-3 polyunsaturated fatty acids: a review of the evidence. Commentary

The impact of long-chain n-3 polyunsaturated fatty acids on human health