Engineering Oilseed Plants for a Sustainable, Land-Based Source of Long Chain Polyunsaturated Fatty Acids

Isolation and transcriptome analysis of a biotechnologically promising Black Sea protist, Thraustochytrium aureum ssp. strugatskii

Background

Marine protists are an important part of the ocean ecosystem. They may possess unique sets of biosynthetic pathways and, thus, be promising model organisms for metabolic engineering for producing substances for the pharmaceutical, cosmetic, and perfume industries. Currently, full-genome data are available just for a limited number of protists hampering their use in biotechnology.

Methods

We characterized the morphology of a new cultured strain of Thraustochytriaceae isolated from the Black Sea ctenophore Beroe ovata using phase-contrast microscopy. Cell culture was performed in the FAND culture medium based on fetal bovine serum and DMEM. Phylogenetic analysis was performed using the 18S rRNA sequence. We also conducted a transcriptome assembly and compared the data with the closest species.

Results

The protist belongs to the genus Thraustochytrium based on the 18S rRNA sequence analysis. We designated the isolated protist as T. aureum ssp. strugatskii. The closest species with the genome assembly is Schizochytrium aggregatum. Transcriptome analysis revealed the majority of the fatty acid synthesis enzymes.

Conclusion

Our findings suggest that the T. aureum ssp. strugatskii is a promising candidate for biotechnological use. Together with the previously available, our data would allow the establishment of an accurate phylogeny of the family Thraustochytriaceae. Also, it could be a reference point for studying the evolution of the enzyme families.

Dietary Intake and Biomarkers of α-Linolenic Acid and Mortality: A Meta-Analysis of Prospective Cohort Studies

Background: The association between α-linolenic acid (ALA) and mortality is inconsistent and has not been summarized systematically.

Objective: The purpose was to conduct a meta-analysis that synthesized the results of prospective cohort studies to investigate associations between ALA intake and mortality.

Methods: We conducted a comprehensive search on PubMed, Embase, and Web of Science databases on May 1, 2021, for relevant prospective cohort studies which reported associations of ALA (assessed by dietary surveys and/or ALA concentrations in body tissues) with mortality from all-cause, cardiovascular disease (CVD), and other diseases. Multivariable-adjusted relative risks (RRs) were pooled by a random or fixed-effects model.

Results: A total of 34 prospective cohort studies, of which 17 reported dietary ALA intake, 14 for ALA biomarkers, and the remaining 3 reported both of intake and biomarkers. The studies included 6,58,634 participants, and deaths were classified into all-cause mortality (56,898), CVD mortality (19,123), and other diseases mortality (19,061). Pooled RRs of ALA intake were 0.93 (95% CI: 0.86, 1.01, I² = 71.2%) for all-cause mortality, 0.90 (95% CI: 0.83, 0.98, I² = 22.1%) for CVD mortality, and 0.94 (95% CI: 0.83, 1.06, I² = 73.3%) for other diseases mortality. The two-stage random-effects dose-response analysis showed a linear relationship between dietary ALA intake and CVD-mortality and each 0.5% energy increment of ALA intake was associated with a 5% lower risk of CVD-mortality (RR: 0.95; 95% CI: 0.90, 1.00). Pooled RRs per SD increment of ALA biomarkers were 0.99 (95% CI: 0.96, 1.01, I² = 27%) for all-cause mortality, 1.00 (95% CI: 0.98, 1.03, I² = 0%) for CVD mortality and 0.98 (95% CI: 0.95, 1.01, I² = 0%) for other diseases mortality.

Conclusions: This meta-analysis summarizing the available prospective cohort studies indicated that ALA intake was associated with reduced risk of mortality, especially CVD mortality. Our findings suggest that ALA consumption may be beneficial for death prevention. Systematic Review Registration:https://www.crd.york.ac.uk/PROSPERO; identifier: CRD42021264532.

Breeding for sustainable oilseed crop yield and quality in a changing climate

As the effects of climate change continue to alter crop-growing conditions year-to-year on both prime and marginal agricultural landscapes, we must consider the effects not only on yield but also on quality. This is particularly true for oilseed crops. In this review, we explore the importance of oilseeds in general and the specific uses of major oilseed crops including soybean, sunflower, canola, peanut, and cottonseed. We review the physiology of seed oil production, from the perspective of the plant's adaptation to environmental changes. Of particular importance is the role of temperature and water availability on oil synthesis. We then discuss how this influences genetic variation, phenotype variability due to environment, and the interaction of genetics and environment to affect composition and yield of vegetable oils. The ability to predict these effects using genomics and bioinformatics is an important new frontier for breeders to maximize stability of a desired fatty acid composition for their crop over increasingly extreme agricultural environments.

Omega-3 PUFA profoundly affect neural, physiological, and behavioural competences - implications for systemic changes in trophic interactions

In recent decades, much conceptual thinking in trophic ecology has been guided by theories of nutrient limitation and the flow of elements, such as carbon and nitrogen, within and among ecosystems. More recently, ecologists have also turned their attention to examining the value of specific dietary nutrients, in particular polyunsaturated fatty acids (PUFA), among which the omega-3 PUFA, especially eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) play a central role as essential components of neuronal cell membranes in many organisms. This review focuses on a new neuro-ecological approach stemming from the biochemical (mechanistic) and physiological (functional) role of DHA in neuronal cell membranes, in particular in conjunction with G-protein coupled receptors (GPCRs). We link the co-evolution of these neurological functions to metabolic dependency on dietary omega-3 PUFA. We outline ways in which deficiencies in dietary DHA supply may affect, cognition, vision, and behaviour, and ultimately, the biological fitness of consumers. We then review emerging evidence that changes in access to dietary omega-3 PUFA may ultimately have profound impacts on trophic interactions leading to potential changes in community structure and ecosystem functioning that, in turn, may affect the supply of DHA within and across ecosystems, including the supply for human consumption.

Biological Role of Unsaturated Fatty Acid Desaturases in Health and Disease

Polyunsaturated fatty acids (PUFAs) are considered one of the most important components of cells that influence normal development and function of many organisms, both eukaryotes and prokaryotes. Unsaturated fatty acid desaturases play a crucial role in the synthesis of PUFAs, inserting additional unsaturated bonds into the acyl chain. The level of expression and activity of different types of desaturases determines profiles of PUFAs. It is well recognized that qualitative and quantitative changes in the PUFA profile, resulting from alterations in the expression and activity of fatty acid desaturases, are associated with many pathological conditions. Understanding of underlying mechanisms of fatty acid desaturase activity and their functional modification will facilitate the development of novel therapeutic strategies in diseases associated with qualitative and quantitative disorders of PUFA.

Isolation and molecular characterization of Thraustochytrium strain isolated from Antarctic Peninsula and its biotechnological potential in the production of fatty acids

Thraustochytrids are unicellular protists belonging to the Labyrinthulomycetes class, which are characterized by the presence of a high lipid content that could replace conventional fatty acids. They show a wide geographic distribution, however their diversity in the Antarctic Region is rather scarce. The analysis based on the complete sequence of 18S rRNA gene showed that strain 34-2 belongs to the species Thraustochytrium kinnei, with 99% identity. The total lipid profile shows a wide range of saturated fatty acids with abundance of palmitic acid (16:0), showing a range of 16.1-19.7%. On the other hand, long-chain polyunsaturated fatty acids, mainly docosahexaenoic acid and eicosapentaenoic acid are present in a range of 24-48% and 6.1-9.3%, respectively. All factors analyzed in cells (biomass, carbon consumption and lipid content) changed with variations of culture temperature (10°C and 25°C). The growth in glucose at a temperature of 10°C presented the most favorable conditions to produce omega-3fatty acid. This research provides the identification and characterization of a Thraustochytrids strain, with a total lipid content that presents potential applications in the production of nutritional supplements and as well biofuels.

Vegetable Oil: Nutritional and Industrial Perspective

Oils of plant origin have been predominantly used for food-based applications. Plant oils not only represent a non-polluting renewable resource but also provide a wide diversity in fatty acids (FAs) composition with diverse applications. Besides being edible, they are now increasingly being used in industrial applications such as paints, lubricants, soaps, biofuels etc. In addition, plants can be engineered to produce fatty acids which are nutritionally beneficial to human health. Thus these oils have potential to 1) substitute ever increasing demand of non –renewable petroleum sources for industrial application and 2) also spare the marine life by providing an alternative source to nutritionally and medically important long chain polyunsaturated fatty acids or ‘Fish oil’. The biochemical pathways producing storage oils in plants have been extensively characterized, but the factors regulating fatty acid synthesis and controlling total oil content in oilseed crops are still poorly understood. Thus understanding of plant lipid metabolism is fundamental to its manipulation and increased production. This review on oils discusses fatty acids of nutritional and industrial importance, and approaches for achieving future designer vegetable oil for both edible and non-edible uses. The review will discuss the success and bottlenecks in efficient production of novel FAs in non-native plants using genetic engineering as a tool.

Global survey of the omega-3 fatty acids, docosahexaenoic acid and eicosapentaenoic acid in the blood stream of healthy adults

Studies reporting blood levels of the omega-3 polyunsaturated fatty acids, eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), were systematically identified in order to create a global map identifying countries and regions with different blood levels. Included studies were those of healthy adults, published in 1980 or later. A total of 298 studies met all inclusion criteria. Studies reported fatty acids in various blood fractions including plasma total lipids (33%), plasma phospholipid (32%), erythrocytes (32%) and whole blood (3.0%). Fatty acid data from each blood fraction were converted to relative weight percentages (wt.%) and then assigned to one of four discrete ranges (high, moderate, low, very low) corresponding to wt.% EPA+DHA in erythrocyte equivalents. Regions with high EPA+DHA blood levels (>8%) included the Sea of Japan, Scandinavia, and areas with indigenous populations or populations not fully adapted to Westernized food habits. Very low blood levels (≤4%) were observed in North America, Central and South America, Europe, the Middle East, Southeast Asia, and Africa. The present review reveals considerable variability in blood levels of EPA+DHA and the very low to low range of blood EPA+DHA for most of the world may increase global risk for chronic disease.

Enhancement of α-linolenic acid content in transgenic tobacco seeds by targeting a plastidial ω-3 fatty acid desaturase (fad7) gene of Sesamum indicum to ER

KEY MESSAGE

Expression of sesame plastidial FAD7 desaturase modified with the endoplasmic reticulum targeting and retention signals, enhances the α-linolenic acid accumulation in seeds of Nicotiana tabacum. In plants, plastidial ω-3 fatty acid desaturase-7 (FAD7) catalyzes the formation of C16 and C18 trienoic fatty acids using organellar glycerolipids and participate in the membrane lipid formation. The plastidial ω-3 desaturases (FAD7) share high sequence homology with the microsomal ω-3 desaturases (FAD3) at the amino acid level except the N-terminal organelle transit peptide. In the present study, the predicted N-terminal plastidial signal peptide of fad7 gene was replaced by the endoplasmic reticulum signal peptide and an endoplasmic reticulum retention signal was placed at the C-terminal. The expression of the modified sesame ω-3 desaturase increases the α-linolenic acid content in the range of 4.78-6.77 % in the seeds of transgenic tobacco plants with concomitant decrease in linoleic acid content. The results suggested the potential of the engineered plastidial ω-3 desaturase from sesame to influence the profile of α-linolenic acid in tobacco plant by shifting the carbon flux from linoleic acid, and thus it can be used in suitable genetic engineering strategy to increase the α-linolenic acid content in sesame and other vegetable oils.

Field trial evaluation of the accumulation of omega-3 long chain polyunsaturated fatty acids in transgenic Camelina sativa: Making fish oil substitutes in plants

The global consumption of fish oils currently exceeds one million tonnes, with the natural de novo source of these important fatty acids forming the base of marine foodwebs. Here we describe the first field-based evaluation of a terrestrial source of these essential nutrients, synthesised in the seeds of transgenic Camelina sativa plants via the heterologous reconstitution of the omega-3 long chain polyunsaturated fatty acid biosynthetic pathway. Our data demonstrate the robust nature of this novel trait, and the feasibility of making fish oils in genetically modified crops. Moreover, to our knowledge, this is the most complex example of plant genetic engineering to undergo environmental release and field evaluation.

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First demonstration of field stability of EPA and DHA trait in transgenic plants.

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Most complex engineered plant trait to undergo field trialling to date.

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Demonstration of the feasibility of using agriculture to make fish oils.

Inventory of fatty acid desaturases in the pennate diatom Phaeodactylum tricornutum

The diatom Phaeodactylum is rich in very long chain polyunsaturated fatty acids (PUFAs). Fatty acid (FA) synthesis, elongation, and desaturation have been studied in depth in plants including Arabidopsis, but for secondary endosymbionts the full picture remains unclear. FAs are synthesized up to a chain length of 18 carbons inside chloroplasts, where they can be incorporated into glycerolipids. They are also exported to the ER for phospho- and betaine lipid syntheses. Elongation of FAs up to 22 carbons occurs in the ER. PUFAs can be reimported into plastids to serve as precursors for glycerolipids. In both organelles, FA desaturases are present, introducing double bonds between carbon atoms and giving rise to a variety of molecular species. In addition to the four desaturases characterized in Phaeodactylum (FAD2, FAD6, PtD5, PtD6), we identified eight putative desaturase genes. Combining subcellular localization predictions and comparisons with desaturases from other organisms like Arabidopsis, we propose a scheme at the whole cell level, including features that are likely specific to secondary endosymbionts.

Effect of Echium oil compared with marine oils on lipid profile and inhibition of hepatic steatosis in LDLr knockout mice

Background

In an effort to identify new alternatives for long-chain n-3 polyunsaturated fatty acids (LC n-3 PUFA) supplementation, the effect of three sources of omega 3 fatty acids (algae, fish and Echium oils) on lipid profile and inflammation biomarkers was evaluated in LDL receptor knockout mice.

Methods

The animals received a high fat diet and were supplemented by gavage with an emulsion containing water (CON), docosahexaenoic acid (DHA, 42.89%) from algae oil (ALG), eicosapentaenoic acid (EPA, 19.97%) plus DHA (11.51%) from fish oil (FIS), and alpha-linolenic acid (ALA, 26.75%) plus stearidonic acid (SDA, 11.13%) from Echium oil (ECH) for 4 weeks.

Results

Animals supplemented with Echium oil presented lower cholesterol total and triacylglycerol concentrations than control group (CON) and lower VLDL than all of the other groups, constituting the best lipoprotein profile observed in our study. Moreover, the Echium oil attenuated the hepatic steatosis caused by the high fat diet. However, in contrast to the marine oils, Echium oil did not affect the levels of transcription factors involved in lipid metabolism, such as Peroxisome Proliferator Activated Receptor α (PPAR α) and Liver X Receptor α (LXR α), suggesting that it exerts its beneficial effects by a mechanism other than those observed to EPA and DHA. Echium oil also reduced N-6/N-3 FA ratio in hepatic tissue, which can have been responsible for the attenuation of steatosis hepatic observed in ECH group. None of the supplemented oils reduced the inflammation biomarkers.

Conclusion

Our results suggest that Echium oil represents an alternative as natural ingredient to be applied in functional foods to reduce cardiovascular disease risk factors.

The application of GMOs in agriculture and in food production for a better nutrition: two different scientific points of view

This commentary is a face-to-face debate between two almost opposite positions regarding the application of genetic engineering in agriculture and food production. Seven questions on the potential benefits of the application of genetic engineering in agriculture and on the potentially adverse impacts on the environment and human health were posed to two scientists: one who is sceptical about the use of GMOs in Agriculture, and one who views GMOs as an important tool for quantitatively and qualitatively improving food production.

High level accumulation of gamma linolenic acid (C18:3Δ6.9,12 cis) in transgenic safflower (Carthamus tinctorius) seeds

Gamma linolenic acid (GLA; C18:3Δ6,9,12 cis), also known as γ-Linolenic acid, is an important essential fatty acid precursor for the synthesis of very long chain polyunsaturated fatty acids and important pathways involved in human health. GLA is synthesized from linoleic acid (LA; C18:2Δ9,12 cis) by endoplasmic reticulum associated Δ6-desaturase activity. Currently sources of GLA are limited to a small number of plant species with poor agronomic properties, and therefore an economical and abundant commercial source of GLA in an existing crop is highly desirable. To this end, the seed oil of a high LA cultivated species of safflower (Carthamus tinctorius) was modified by transformation with Δ6-desaturase from Saprolegnia diclina resulting in levels exceeding 70% (v/v) of GLA. Levels around 50% (v/v) of GLA in seed oil was achieved when Δ12-/Δ6-desaturases from Mortierella alpina was over-expressed in safflower cultivars with either a high LA or high oleic (OA; C18:1Δ9 cis) background. The differences in the overall levels of GLA suggest the accumulation of the novel fatty acid was not limited by a lack of incorporation into the triacylgylcerol backbone (>66% GLA achieved), or correlated with gene dosage (GLA levels independent of gene copy number), but rather reflected the differences in Δ6-desaturase activity from the two sources. To date, these represent the highest accumulation levels of a newly introduced fatty acid in a transgenic crop. Events from these studies have been propagated and recently received FDA approval for commercialization as Sonova™400.

STUDY ON BIOLOGICAL CHARACTERISTICS OF HETEROTROPHIC MARINE MICROALGA-SCHIZOCHYTRIUM MANGROVEI PQ6 ISOLATED FROM PHU QUOC ISLAND, KIEN GIANG PROVINCE, VIETNAM(1)

Schizochytrium sp. PQ6, a heterotrophic microalga isolated from Phu Quoc (PQ) Island in the Kien Giang province of Vietnam, contains a high amount of docosahexaenoic acid (DHA, C22:6n-3). In this study, the culture conditions are developed to maximize biomass and DHA production. Nucleotide sequence analysis of partial 18S rRNA gene from genomic DNA showed that PQ6 has a phylogenetic relationship close to Schizochytrium mangrovei Raghu-Kumar. The highest growth rate and DHA accumulation of this strain were obtained in 6.0% glucose, 1.0% yeast extract, 50% artificial seawater (ASW), and pH 7 at 28°C. In addition, carbon and nitrogen sources could be replaced by glycerol, ammonium acetate, sodium nitrate, or fertilizer N-P-K. Total lipid content reached 38.67% of dry cell weight (DCW), in which DHA and eicosapentaenoic acid (EPA, C20:5n-3) contents accounted for 43.58% and 0.75% of the total fatty acid (TFA), respectively. In 5 and 10 L fermenters, the cell density, DCW, total lipid content, and maximum DHA yield were 46.50 × 10(6)  cells · mL(-1) , 23.7 g · L(-1) , 38.56% of DCW, and 8.71 g · L(-1) (in 5 L fermenter), respectively, and 49.71 × 10(6)  cells · mL(-1) , 25.34 g · L(-1) , 46.23% of DCW, and 11.55 g · L(-1) (in 10 L fermenter), respectively. Biomass of PQ6 strain possessed high contents of Na, I, and Fe (167.185, 278.3, and 43.69 mg · kg(-1) DCW, respectively). These results serve as a foundation for the efficient production of PQ6 biomass that can be used as a food supplement for humans and aquaculture in the future.

Agricultural recovery of a formerly radioactive area: I. Establishment of high-resolution quantitative protein map of mature flax seeds harvested from the remediated Chernobyl area

In recent years there has been an increasing tendency toward remediation of contaminated areas for agriculture purposes. The study described herein is part of a comprehensive, long-term characterization of crop plants grown in the area formerly contaminated with radioactivity. As a first step, we have established a quantitative map of proteins isolated from mature flax (Linum usitatissimum L.) seeds harvested from plants grown in a remediated plot localized directly in Chernobyl town. Flax was selected because it is a crop of economic and historical importance, despite the relative paucity of molecular resources. We used 2-dimensional electrophoresis followed by tandem mass spectrometry to establish a high-resolution seed proteome map. This approach yielded quantitative information for 318 protein spots. Genomic sequence resources for flax are very limited, leaving us with an "unknown function" annotation for 38% of the proteins analyzed including several that comprise very large spots. In addition to the seed storage proteins, we were able to reliably identify 82 proteins many of which are involved with central metabolism.

Engineering plastid fatty acid biosynthesis to improve food quality and biofuel production in higher plants

The ability to manipulate plant fatty acid biosynthesis by using new biotechnological approaches has allowed the production of transgenic plants with unusual fatty acid profile and increased oil content. This review focuses on the production of very long chain polyunsaturated fatty acids (VLCPUFAs) and the increase in oil content in plants using molecular biology tools. Evidences suggest that regular consumption of food rich in VLCPUFAs has multiple positive health benefits. Alternative sources of these nutritional fatty acids are found in cold-water fishes. However, fish stocks are in severe decline because of decades of overfishing, and also fish oils can be contaminated by the accumulation of toxic compounds. Recently, there is also an increase in oilseed use for the production of biofuels. This tendency is partly associated with the rapidly rising costs of petroleum, increased concern about the environmental impact of fossil oil and the attractive need to develop renewable sources of fuel. In contrast to this scenario, oil derived from crop plants is normally contaminant free and less environmentally aggressive. Genetic engineering of the plastid genome (plastome) offers a number of attractive advantages, including high-level foreign protein expression, marker-gene excision and transgene containment because of maternal inheritance of plastid genome in most crops. Here, we describe the possibility to improve fatty acid biosynthesis in plastids, production of new fatty acids and increase their content in plants by genetic engineering of plastid fatty acid biosynthesis via plastid transformation.

Fatty acid status in early life in low-income countries--overview of the situation, policy and research priorities

Fat intake may be low in low-income countries and little information is available on its composition in terms of (n-3) and (n-6) fatty acids (FA). As a result, long chain poly-unsaturated fatty acid (LCPUFA) status is a concern, especially in settings where fish intake is low and/or common sources of fat have a low alpha-linolenic acid (ALA) and high linoleic acid (LA) content. High LA levels, as found for instance in sunflower, safflower, corn, peanut and soy oils, may inhibit the conversion of ALA into its LC-PUFA derivatives. Other factors that affect LA and ALA conversion into LC-PUFA, including genetic factors, are little known and should also be investigated in different populations. Different interventions that could feasibly improve LC-PUFA status in low-income countries should be tested and their effects on functional outcomes assessed, preferably starting from pregnancy. Identifying affordable sources of ALA or LC-PUFA that could be made locally available and easily introduced in the diet early in life is also a priority.

The role of transgenic crops in sustainable development

The concept of sustainable development forms the basis for a wide variety of international and national policy making. World population continues to expand at about 80 M people per year, while the demand for natural resources continues to escalate. Important policies, treaties and goals underpin the notion of sustainable development. In this paper, we discuss and evaluate a range of scientific literature pertaining to the use of transgenic crops in meeting sustainable development goals. It is concluded that a considerable body of evidence has accrued since the first commercial growing of transgenic crops, which suggests that they can contribute in all three traditional pillars of sustainability, i.e. economically, environmentally and socially. Management of herbicide-tolerant and insect-resistant transgenic crops to minimize the risk of weeds and pests developing resistance is discussed, together with the associated concern about the risk of loss of biodiversity. As the world population continues to rise, the evidence reviewed here suggests it would be unwise to ignore transgenic crops as one of the tools that can help meet aspirations for increasingly sustainable global development.

Stacking multiple transgenes at a selected genomic site via repeated recombinase-mediated DNA cassette exchanges

Recombinase-mediated DNA cassette exchange (RMCE) has been successfully used to insert transgenes at previously characterized genomic sites in plants. Following the same strategy, groups of transgenes can be stacked to the same site through multiple rounds of RMCE. A gene-silencing cassette, designed to simultaneously silence soybean (Glycine max) genes fatty acid ω-6 desaturase 2 (FAD2) and acyl-acyl carrier protein thioesterase 2 (FATB) to improve oleic acid content, was first inserted by RMCE at a precharacterized genomic site in soybean. Selected transgenic events were subsequently retransformed with the second DNA construct containing a Yarrowia lipolytica diacylglycerol acyltransferase gene (DGAT1) to increase oil content by the enhancement of triacylglycerol biosynthesis and three other genes, a Corynebacterium glutamicum dihydrodipicolinate synthetase gene (DHPS), a barley (Hordeum vulgare) high-lysine protein gene (BHL8), and a truncated soybean cysteine synthase gene (CGS), to improve the contents of the essential amino acids lysine and methionine. Molecular characterization confirmed that the second RMCE successfully stacked the four overexpression cassettes to the previously integrated FAD2-FATB gene-silencing cassette. Phenotypic analyses indicated that all the transgenes expressed expected phenotypes.

Biofuels from algae: challenges and potential

Algae biofuels may provide a viable alternative to fossil fuels; however, this technology must overcome a number of hurdles before it can compete in the fuel market and be broadly deployed. These challenges include strain identification and improvement, both in terms of oil productivity and crop protection, nutrient and resource allocation and use, and the production of co-products to improve the economics of the entire system. Although there is much excitement about the potential of algae biofuels, much work is still required in the field. In this article, we attempt to elucidate the major challenges to economic algal biofuels at scale, and improve the focus of the scientific community to address these challenges and move algal biofuels from promise to reality.

Elevated production of docosahexaenoic acid in females: potential molecular mechanisms

Observational evidence suggests that in populations consuming low levels of n-3 highly unsaturated fatty acids, women have higher blood levels of docosahexaenoic acid (DHA; 22:3n-6) as compared with men. Increased conversion of alpha-linolenic acid (ALA; 18:3n-3) to DHA by females has been confirmed in fatty acid stable isotope studies. This difference in conversion appears to be associated with estrogen and some evidence indicates that the expression of enzymes involved in synthesis of DHA from ALA, including desaturases and elongases, is elevated in females. An estrogen-associated effect may be mediated by peroxisome proliferator activated receptor-alpha (PPARalpha), as activation of this nuclear receptor increases the expression of these enzymes. However, because estrogens are weak ligands for PPARalpha, estrogen-mediated increases in PPARalpha activity likely occur through an indirect mechanism involving membrane-bound estrogen receptors and estrogen-sensitive G-proteins. The protein kinases activated by these receptors phosphorylate and increase the activity of PPARalpha, as well as phospholipase A(2) and cyclooxygenase 2 that increase the intracellular concentration of PPARalpha ligands. This review will outline current knowledge regarding elevated DHA production in females, as well as highlight interactions between estrogen signaling and PPARalpha activity that may mediate this effect.

Postgraduate Symposium Long-chainn-3 PUFA: intakes in the UK and the potential of a chicken meat prototype to increase them

With the wide acceptance of the long-chain (LC)n-3 PUFA EPA and DHA as important nutrients playing a role in the amelioration of certain diseases, efforts to understand factors affecting intakes of these fatty acids along with potential strategies to increase them are vital. Widespread aversion to oil-rich fish, the richest natural source of EPA and DHA, highlights both the highly suboptimal current intakes in males and females across all age-groups and the critical need for an alternative supply of EPA and DHA. Poultry meat is a popular and versatile food eaten in large quantities relative to other meats and is open to increased LCn-3 PUFA content through manipulation of the chicken's diet to modify fatty acid deposition and therefore lipid composition of the edible tissues. It is therefore seen as a favourable prototype food for increasing human dietary supply of LCn-3 PUFA. Enrichment of chicken breast and leg tissue is well established using fish oil or fishmeal, but concerns about sustainability have led to recent consideration of algal biomass as an alternative source of LCn-3 PUFA. Further advances have also been made in the quality of the resulting meat, including achieving acceptable flavour and storage properties as well as understanding the impact of cooking on the retention of fatty acids. Based on these considerations it may be concluded that EPA- and DHA-enriched poultry meat has a very positive potential future in the food chain.

The role of light in soybean seed filling metabolism

Soybean (Glycine max) yields high levels of both protein and oil, making it one of the most versatile and important crops in the world. Light has been implicated in the physiology of developing green seeds including soybeans but its roles are not quantitatively understood. We have determined the light levels reaching growing soybean embryos under field conditions and report detailed redox and energy balance analyses for them. Direct flux measurements and labeling patterns for multiple labeling experiments including [U-(13)C(6)]-glucose, [U-(13)C(5)]-glutamine, the combination of [U-(14)C(12)]-sucrose + [U-(14)C(6)]-glucose + [U-(14)C(5)]-glutamine + [U-(14)C(4)]-asparagine, or (14)CO2 labeling were performed at different light levels to give further insight into green embryo metabolism during seed filling and to develop and validate a flux map. Labeling patterns (protein amino acids, triacylglycerol fatty acids, starch, cell wall, protein glycan monomers, organic acids), uptake fluxes (glutamine, asparagine, sucrose, glucose), fluxes to biomass (protein amino acids, oil), and respiratory fluxes (CO2, O2) were established by a combination of gas chromatography-mass spectrometry, (13)C- and (1)H-NMR, scintillation counting, HPLC, gas chromatography-flame ionization detection, C:N and amino acid analyses, and infrared gas analysis, yielding over 750 measurements of metabolism. Our results show: (i) that developing soybeans receive low but significant light levels that influence growth and metabolism; (ii) a role for light in generating ATP but not net reductant during seed filling; (iii) that flux through Rubisco contributes to carbon conversion efficiency through generation of 3-phosphoglycerate; and (iv) a larger contribution of amino acid carbon to fatty acid synthesis than in other oilseeds analyzed to date.

n-3 Oil sources for use in aquaculture--alternatives to the unsustainable harvest of wild fish

The present review examines renewable sources of oils with n-3 long-chain (> or = C20) PUFA (n-3 LC-PUFA) as alternatives to oil from wild-caught fish in aquafeeds. Due to the increased demand for and price of wild-caught marine sources of n-3 LC-PUFA-rich oil, their effective and sustainable replacement in aquafeeds is an industry priority, especially because dietary n-3 LC-PUFA from eating fish are known to have health benefits in human beings. The benefits and challenges involved in changing dietary oil in aquaculture are highlighted and four major potential sources of n-3 LC-PUFA for aquafeeds, other than fish oil, are compared. These sources of oil, which contain n-3 LC-PUFA, specifically EPA (20:5n-3) and DHA (22:6n-3) or precursors to these key essential fatty acids, are: (1) other marine sources of oil; (2) vegetable oils that contain biosynthetic precursors, such as stearidonic acid, which may be used by fish to produce n-3 LC-PUFA; (3) single-cell oil sources of n-3 LC-PUFA; (4) vegetable oils derived from oil-seed crops that have undergone genetic modification to contain n-3 LC-PUFA. The review focuses on Atlantic salmon (Salmo salar L.), because it is the main intensively cultured finfish species and it both uses and stores large amounts of oil, in particular n-3 LC-PUFA, in the flesh.

Thraustochytrid Marine Protists: production of PUFAs and Other Emerging Technologies

Thraustochytrids, the heterotrophic, marine, straminipilan protists, are now established candidates for commercial production of the omega-3 polyunsaturated fatty acid (omega-3 PUFA), docosahexaenoic acid (DHA), that is important in human health and aquaculture. Extensive screening of cultures from a variety of habitats has yielded strains that produce at least 50% of their biomass as lipids, and DHA comprising at least 25% of the total fatty acids, with a yield of at least 5 g L(-1). Most of the lipids occur as triacylglycerols and a lesser amount as phospholipids. Numerous studies have been carried out on salinity, pH, temperature, and media optimization for DHA production. Commercial production is based on a fed batch method, using high C/N ratio that favors lipid accumulation. Schizochytrium DHA is now commercially available as nutritional supplements for adults and as feeds to enhance DHA levels in larvae of aquaculture animals. Thraustochytrids are emerging as a potential source of other PUFAs such as arachidonic acid and oils with a suite of PUFA profiles that can have specific uses. They are potential sources of asataxanthin and carotenoid pigments, as well as other lipids. Genes of the conventional fatty acid synthesis and the polyketide-like PUFA synthesis pathways of thraustochytrids are attracting attention for production of recombinant PUFA-containing plant oils. Future studies on the basic biology of these organisms, including biodiversity, environmental adaptations, and genome research are likely to point out directions for biotechnology explorations. Potential areas include enzymes, polysaccharides, and secondary metabolites.

Filamentous fungi for production of food additives and processing aids

Filamentous fungi are metabolically versatile organisms with a very wide distribution in nature. They exist in association with other species, e.g. as lichens or mycorrhiza, as pathogens of animals and plants or as free-living species. Many are regarded as nature's primary degraders because they secrete a wide variety of hydrolytic enzymes that degrade waste organic materials. Many species produce secondary metabolites such as polyketides or peptides and an increasing range of fungal species is exploited commercially as sources of enzymes and metabolites for food or pharmaceutical applications. The recent availability of fungal genome sequences has provided a major opportunity to explore and further exploit fungi as sources of enzymes and metabolites. In this review chapter we focus on the use of fungi in the production of food additives but take a largely pre-genomic, albeit a mainly molecular, view of the topic.

Echium oil is better than rapeseed oil in enriching poultry meat withn-3 polyunsaturated fatty acids, including eicosapentaenoic acid and docosapentaenoic acid

α-Linolenic acid (ALA; 18 : 3n-3) and stearidonic acid (SDA; 18 : 4n-3) are on the biosynthetic pathway of EPA (20 : 5n-3) and DHA (22 : 6n-3). Then-3 fatty acid in rapeseed oil is ALA while Echium oil contains both ALA and SDA. To determine the comparative efficacy of ALA- and SDA-rich oils in enriching broiler meat withn-3 PUFA, we offered diets supplemented with rapeseed oil (rapeseed group) or Echium oil (Echium group) for 35 d to two groups of chicks (age 21 d). There were no differences in carcass weight (2·20 (sem0·06)v.2·23 (sem0·05) kg), boned, skinless thigh muscle (494 (sem20·5)v.507 (sem16·7) g), boned, skinless breast muscle (553 (sem13·4)v.546 (sem11·6) g) or organ weights (heart, liver and gizzard) between the two groups. The total intramuscular fat (IMF) percentage of thigh (8·0 (sem0·64)v.8·1 (sem0·62) %) and breast muscles (2·3 (sem0·24)v.2·0 (sem0·19) %) were also similar between the groups. In contrast, the concentrations of most of the individualn-3 fatty acids (ALA, SDA, EPA and docosapentaenoic acid) were all higher in the Echium than the rapeseed group (P < 0·05). However, differences in DHA concentrations were significant in breast but not thigh muscle IMF. The totaln-3 yields/100 g serve thigh muscle were 265 and 676 mg for the rapeseed and Echium groups, respectively (P < 0·0001). The corresponding values for equivalent breast muscles were 70 and 137 mg, respectively (P < 0·01). We conclude that Echium oil is a better lipid supplement than rapeseed oil in changing the concentration and yield ofn-3 fatty acids, except DHA, in broiler meat.

Metabolic engineering of natural products in plants; tools of the trade and challenges for the future

Plant natural products play essential roles in plant survivability and many of them are used as nutrients, colorants, flavors, fragrances, and medicines. Genetic engineering of plants for natural products can help alleviate the demands for limited natural resources. Successes in enhancing production capacities have included manipulating blocks of genes coding for segments of pathways, over-expression of putative rate-limiting steps in pathways, expression of transcription factors regulating the entire metabolic pathways, and the construction of novel branch pathways capable of diverting carbon to the biosynthesis of unique metabolites in unexpected intracellular compartments. Further enhancements are likely if more efficient pathways can be constructed, providing for the efficient channeling of intermediates to final products, and if the means for sequestering natural products in planta can be accomplished.