Aurantiochytrium Limacinum Research Articles

Increasing the Omega-3 Content of Hen's Eggs Through Dietary Supplementation with Aurantiochytrium limacinum Microalgae: Effect of Inclusion Rate on the Temporal Pattern of Docosahexaenoic Acid Enrichment, Efficiency of Transfer, and Egg Characteristics

SUMMARY Changes in modern human diets have resulted in a deficiency in omega-3 fatty acids. Rectifying this deficiency and increasing dietary levels of omega-3 fatty acids, such as docosahexaenoic acid (DHA), can improve overall human health. Fish are a rich source of omega-3 fatty acids; however, low levels of consumption in many parts of the world, coupled with declining fish stocks, mean that alternative dietary omega-3 sources are required. The enrichment of commonly consumed foods has been suggested as a strategy that could increase omega-3 consumption. Eggs are an obvious target for enrichment as they are consumed worldwide and can have their omega-3 content altered through dietary manipulation of hens. In the current study, algae were included in the diet of hens, at 3 inclusion levels, in order to increase the omega-3 content of their eggs. For each treatment, the DHA content of eggs reached a plateau, proportional to the level of inclusion in the diet, which was then maintained for the duration of the experimental period. Higher inclusion levels reached this plateau quicker; however, the efficiency of transfer was reduced with increased dietary DHA. This maintenance of an increased egg DHA content over a prolonged period of time emphasizes the suitability of dietary supplementation with algae as a means to improve the nutritional value of hen's eggs.

Redressing the balance: including DHA-rich Aurantiochytrium limacinum in broiler diets increases tissue omega-3 fatty acid content and lowers the n-6:n-3 ratio

ABSTRACT 1. The consumption of sufficient quantities of long chain omega-3 fatty acids (n-3 LCPUFA) from meat and other animal products can lead to a variety of health benefits in humans. The fatty acid content of poultry meat can be increased by feeding birds ingredients that are rich in n-3 LCFUFA 2. The effect of feeding a docosahexaenoic acid (DHA) rich Aurantiochytrium limacinum biomass (AURA) on the fatty acid content of breast and thigh tissues was investigated in a feeding trial with 2880 male Ross 308 broilers. The broiler diets were supplemented with either 0, 0.25, 0.5 or 1% AURA from day 21 to 42 of age. 3. Supplementation significantly increased the DHA content of both breast and thigh meat at an inclusion rate of 1% in the diet, leading to a total of 42 and 46 mg DHA/100 g of fresh breast or thigh tissue respectively. Significant increases in the tissue eicosapentaenoic acid (EPA) concentration were seen alongside a reduced omega-6/omega-3 ratio, improving the nutritional value of the meat for consumers and identifying supplementation of broiler diets with A. limacinum as an effective and sustainable method to increase n-3 LCPUFA consumption in the human population.

Dietary supplementation of dairy cows with a docosahexaenoic acid-rich thraustochytrid, <i>Aurantiochytrium limacinum</i>: effects on milk quality, fatty acid composition and cheese making properties

Dietary supplementation of dairy cows with a docosahexaenoic acid-rich thraustochytrid, <i>Aurantiochytrium limacinum</i>: effects on milk quality, fatty acid composition and cheese making properties

Why does a heterotrophic marine protist produce carotenoids? Genetic approaches to investigate the ecophysiology of the thraustochytrid Aurantiochytrium limacinum

Thraustochytrids are abundant and ubiquitous osmoheterotrophic marine protists (labyrinthulomycetes, stramenopiles) thought to function ecologically as fungus-like decomposers. Some thraustochytrids have the ability to synthesize carotenoids, including carotenes (e.g. beta-carotene) and xanthophylls (e.g. astaxanthin), which is uncommon among heterotrophic eukaryotes. Carotenogenic thraustochytrids appear to have acquired carotenoid biosynthetic enzymes by horizontal gene transfer from bacteria. Heterotrophic production of carotenoids is typically associated with protection against oxidative stress, and in thraustochytrids may be particularly associated with protecting large amounts of essential omega-3 polyunsaturated fatty acids stored in lipid droplets. To gain better understanding of carotenoid function in thraustochytrids, and thus new insight into the ecophysiology of these organisms, we have produced mutants of the thraustochytrid Aurantiochytrium limacinum in which the trifunctional gene Aurli_150841, encoding the first three carotenogenesis-specific reactions (phytoene synthase, phytoene desaturase, lycopene cyclase), has been interrupted by double homologous recombination with a construct containing a zeocin resistance (BleoR, shble) expression cassette. As predicted, the Aurli_150841 knockout mutants lack the carotenoid pigmentation found in the wild-type. Complementation with the wild-type Aurli_150841 to confirm that this phenotype is due to the knockout is in progress. Differences between the wild-type and Aurli_150841 knockout mutants in features such as growth rate and biomass yield, lipid content, survival in stationary phase and response to oxidative stress are being evaluated under growth conditions that induce different amounts of carotenoid accumulation in the wild-type.

The glycerol-3-phosphate acyltransferase PLAT2 functions in the generation of DHA-rich glycerolipids in Aurantiochytrium limacinum F26-b.

Thraustochytrids possess docosahexaenoic acid (DHA, 22:6n-3) as acyl chain(s) of triacylglycerol (TG) and phosphatidylcholine (PC), some of which contain multiple DHAs. However, little is known about how these DHA-rich glycerolipids are produced in thraustochytrids. In this study, we identified PLAT2 in Aurantiochytrium limacinum F26-b as a glycerol-3-phosphate (G3P) acyltransferase (GPAT) by heterologous expression of the gene in budding yeast. Subsequently, we found that GPAT activity was reduced by disruption of the PLAT2 gene in A. limacinum, resulting in a decrease in DHA-containing lysophosphatidic acid (LPA 22:6). Conversely, overexpression of PLAT2 increased both GPAT activity and LPA 22:6. These results indicate that PLAT2 is a GPAT that transfers DHA to G3P in vivo as well as in vitro. Overexpression of the PLAT2 gene increased the production of a two DHA-containing diacylglycerol (DG 44:12), followed by an increase in the three DHA-containing TG (TG 66:18), two-DHA-containing TG (TG 60:12), and two DHA-containing PC (PC 44:12). However, overexpression of PLAT2 did not increase DHA-free DG (DG32:0), which was preferentially converted to three 16:0-containing TG (TG 48:0) but not two 16:0-containing PC (PC 32:0). Collectively, we revealed that DHA-rich glycerolipids are produced from a precursor, LPA 22:6, which is generated by incorporating DHA to G3P by PLAT2 in the A. limacinum.

Anti-Inflammatory Effects of Aurantiochytrium limacinum 4W-1b Ethanol Extract on Murine Macrophage RAW264 Cells.

Aurantiochytrium limacinum 4W-1b (AL4W-1b) is a newly discovered microalgal strain with unique features. In the present study, we investigated the effects of ethanol extracts of AL4W-1b on lipopolysaccharide- (LPS-) induced inflammatory responses in RAW264 murine macrophage cells. Pretreatment of RAW264 cells with the AL4W-1b extract significantly reduced the production of LPS-induced nitric oxide (NO) and the expression of proinflammatory cytokine genes, including tumor necrosis factor α, interleukin- (IL-) 1β, and IL-6. Treatment with the AL4W-1b extract also decreased the production of IL-1β and IL-6. These results suggest that AL4W-1b might have anti-inflammatory effects in RAW264 cells. The NF-κB inhibitor, BAY 11-7082, synergistically prevented LPS-induced NO production after pretreatment with the AL4W-1b extract. Thus, the AL4W-1b extract may affect not only the NF-κB pathway but also other inflammatory pathways. To the best of our knowledge, this is the first study to report the anti-inflammatory effects of AL4W-1b extract and its mechanism of action in LPS-stimulated murine macrophage cells.

Analytical Method Assessment for the Determination of DHA and Fatty Acids Present in Unextracted <i>Aurantiochytrium limacinum</i> Biomass

Research into long-chain polyunsaturated fatty acids (LC-PUFA), such as docosahexaenoic acid (DHA C22:6 n-3), has shown that their inclusion in the human diet is linked with many health benefits. This has led to an increased interest in the enrichment of certain foodstuffs with DHA by supplementing animal fed with DHA-rich ingredients which can lead to an increased uptake in the meat, milk and eggs animal by-products. The microalgae Aurantiochytrium limacinum has been found to be especially useful in this pursuit. It is subsequently desirable to availably have a simple and robust method for the routine analysis of DHA and other fatty acids in the algal biomass. The AOAC method 996.06 is often followed for the analysis of fatty acids in foods and demonstrating that its fitness for purpose in the analysis of DHA and additional fatty acids in Aurantiochytrium limacinum is therefore the objective of this paper. A validation of the method for the determination of DHA and three other fatty acids in Aurantiochytrium limacinum is presented. The method was found to be linear over the following ranges for each fatty acid methyl ester (FAME) analyte; 50 to 15,000 μg/ml (C14:0), 300 to 95,000 (C16:0), 25 to 15,000 (C18:0) and 300 to 59,375 (C22:6). The accuracy, precision and LOD and LOQ of the method were confirmed and its robustness tested. The application of the method to assess the stability of Aurantiochytrium limacinum containing two alternative antioxidants was further examined. The investigation showed that DHA was stable over six months with the inclusion of either Duralox® or ethoxyquin as an antioxidant and ethoxyquin could additionally stabilize DHA in Aurantiochytrium limacinum up to 24 months.

Metabolite Profile Analysis of Aurantiochytrium limacinum SR21 Grown on Acetate-based Medium for Lipid Fermentation.

Thraustochytrids, a group of marine protists, are continuously gaining attention due to their capability in producing lipids for various biotechnological applications towards foods, medicines, chemicals, and biofuels. Although various substrates, predominantly glucose, have been used as carbon source for this microalga, it is desirable to adopt cheaper and more diversified substrate to expand their application range. In this study, we aimed to examine the ability of acetate, which can be easily generated from various resources by acetogenic microorganisms, as a substrate of Aurantiochytrium limacinum SR21. As a result of flask-scale analysis, specific growth rates (µ) of the strain SR21 grown in 3% acetate- or glucose-based medium were 0.55 and 0.98 h-1, respectively. The maximum yield of total fatty acid in acetate medium was 4.8 g/L at 48 h while that in glucose medium was 6.8 g/L at 30 h, indicating that acetate has potential as substrate. Metabolome analysis was performed to comprehensively elucidate characteristic metabolic fluctuations caused by acetate assimilation and identify targets to improve the fatty acid productivity from acetate. It was found that the use of glyoxylate cycle, which bypasses release of energy molecules such as NADH and GTP, and the inhibition of utilization of compounds from TCA cycle for anabolic reactions, may cause the slow growth in acetate which has an effect also in lipid productivity. The activity of the pentose phosphate pathway was found to be weak in acetate cultivation, thus NADPH was mainly produced in malate-pyruvate cycle. Lastly, mevalonate pathway was found to be activated in acetate cultivation which additionally competes with acetyl-CoA as starting material of fatty acid synthesis.

Cloning of the pks3 gene of Aurantiochytrium limacinum and functional study of the 3-ketoacyl-ACP reductase and dehydratase enzyme domains.

Aurantiochytrium limacinum has received attention because of its abundance of polyunsaturated fatty acids (PUFAs), particularly docosahexaenoic acid (DHA). DHA is synthesized through the polyketide synthase (PKS) pathway in A. limacinum. The related enzymes of the PKS pathway are mainly expressed by three gene clusters, called pks1, pks2 and pks3. In this study, the full-length pks3 gene was obtained by polymerase chain reaction amplification and Genome Walking technology. Based on a domain analysis of the deduced amino acid sequence of the pks3 gene, 3-ketoacyl-ACP reductase (KR) and dehydratase (DH) enzyme domains were identified. Herein, A. limacinum OUC168 was engineered by gene knock-in of KR and DH using the 18S rDNA sequence as the homologous recombination site. Total fatty acid contents and the degree of unsaturation of total fatty acids increased after the kr or dh gene was knocked in. The cloning and functional study of the pks3 gene of A. limacinum establishes a foundation for revealing the DHA synthetic pathway. Gene knock-in of the enzyme domain associated with PKS synthesis has the potential to provide effective recombinant strains with higher DHA content for industrial applications.

Tolerance of Broilers to Dietary Supplementation with High Levels of the DHA-Rich Microalga, Aurantiochytrium Limacinum: Effects on Health and Productivity.

Simple SummaryDocosahexaenoic acid (DHA) is an omega-3 fatty acid that is considered an essential part of the human diet. Increasing the amount of DHA in commonly consumed foodstuffs can benefit people predisposed to heart problems, depression, and even some forms of cancer. One of the best sources of DHA is oily fish, but the majority of people do not eat fish regularly. By formulating diets for livestock or poultry to include ingredients rich in omega-3 fatty acids, we can increase the omega-3 content of their respective meat and tissues. In this study we fed broilers diets supplemented with increasing amounts of a DHA-rich microalgae to investigate whether it was safe for the birds, in terms of their health and productivity and effective in terms of DHA transfer from feed to meat. The results of the present study showed that feeding the microalgae to chickens had no negative effects on their health in terms of their level of survival or growth. Moreover, we found that supplementing the microalgae resulted in a large increase in the DHA content of meat. This study demonstrated that feeding algae is a safe and effective way to improve the nutritional value of chicken meat.It is well established that the docosahexaenoic acid (DHA) content of commonly consumed meats, such as chicken, can be increased through dietary supplementation with DHA-rich ingredients. The purpose of this study was to investigate the tolerance of broilers to dietary supplementation with the unextracted biomass of a DHA-rich microalgae Aurantiochytrium limacinum, so as to ensure its safety, since it is accumulated in broiler meat. Healthy day-old male Ross 308 chicks (n = 1120) were evenly distributed to 32 pens (35 chicks per pen), with pens randomly allocated to one of four dietary treatments, each having eight replicates. The dietary groups included one untreated control and three treatments corresponding to three inclusion levels (0.5, 2.5, and 5.0%) of All-G-Rich®, with the birds receiving the experimental diets ad libitum during the study (day 0–42). Bird survival, blood parameters, productivity, and breast and thigh DHA content were determined after 42 days of feeding. Supplementation at up to 10 times the intended use level had no negative effects on the mortality, blood parameters or productivity of the birds, while significant increases in the meat DHA content were observed. These results indicate that supplementation with Aurantiochytrium limacinum is a safe and effective way to increase broiler tissue DHA content.

Development of Aurantiochytrium limacinum SR21 cultivation using salt-rich waste feedstock for docosahexaenoic acid production and application of natural colourant in food product

Microalgae biorefinery is presently receiving a lot of attention as driven by its production of high value-added products. In this study, an oleaginous microalga Aurantiochytrium limacinum SR21 was cultured for docosahexaenoic acid (DHA) production using 20% (w/v) of K2HPO4-waste feedstock to replace 0.005% (w/v) of KH2PO4 in the flask culture. DHA is an essential nutrient for human’s brain functionalities. Collectively, the K2HPO4-waste feedstock with working concentration of 0.005% (w/v) in the cultivation prompted a higher lipid content (8.29%) and DHA production (128.81 mg.L−1). Moreover, natural plant pigment products containing stabilised betacyanins were utilised as natural red colourants for hard candy production. This study develops microalgal cultivation using salt-rich waste feedstock for a higher lipid and DHA content as well as application of natural colouring agents in food products.

Correction: Novel Lysophospholipid Acyltransferase PLAT1 of Aurantiochytrium limacinum F26-b Responsible for Generation of Palmitate-Docosahexaenoate-Phosphatidylcholine and Phosphatidylethanolamine.

[This corrects the article DOI: 10.1371/journal.pone.0102377.].

Ecophysiology and lipid dynamics of a eukaryotic mangrove decomposer.

Aurantiochytrium limacinum is an osmo-heterotrophic Stramenopile and a pioneering mangrove decomposer which is taxonomically assigned to the family of Thraustochytriaceae (class: Labyrinthulomycetes). The life cycle of A. limacinum involves different cell types including mono- and multi-nucleated cells as well as flagellated zoospores which colonize new fallen leaves. The ecological relevance of thraustochytrids is underestimated and eclipsed by their biotechnological importance, due to their ability to accumulate large amount of lipids, mainly triacylglycerols (TAGs). In this study, we aimed to understand the ecophysiological parameters that trigger zoospore production and the interplay between the life cycle of A. limacinum and its lipid metabolism. When grown in a rich medium, cells accumulated large amounts of TAGs at the end of their growth period, but no zoospores were produced. In poor media such as artificial sea water, zoospores were produced in massive quantities. In the absence of organic carbon, the zoospores remained swimming for at least 6 days, consuming their TAGs in the process. Addition of glucose rapidly triggered the maturation of the zoospores. On the basis of these data, we propose a life cycle for A. limacinum integrating the potential perturbations/changes in the environment surrounding a mangrove leaf that could lead to the production of zoospores and colonization of new areas.

Aurantiochytrium limacinum BCC52274 improves growth, hypo-salinity tolerance and swimming strength of Penaeus vannamei post larvae

Long-chain polyunsaturated fatty acids (LC-PUFAs) have been shown to promote growth and health of many larval marine animals. Producing high amounts of LC-PUFAs, thraustochytrids are potential alternatives to fish oil as feed supplement for marine larviculture. Their applications have been assessed in many larval aquatic species but not yet in larval and post-larval (PL) shrimp. Here, growth performance and health of Penaeus vannamei PL were evaluated when fed with a thraustochytrid, Aurantiochytrium limacinum BCC52274 (AL), via enrichment in instar-II Artemia. Instar-II Artemia was enriched with AL for 4 h at the ratio of 400,000 individuals: 600 mg of freeze-dried AL per 1l of 30-ppt water. The feeding experiment consisted of treatment groups fed with varied proportions (from 0 to 100%) of the number of meals offering the non-enriched and enriched instar-II Artemia. Additionally, a reference group was included, in which PL were fed only with instar-I Artemia, the stage commonly used in commercial practice. AL enrichment replenished DHA deficiency in Artemia and increased LC-PUFA content in the fed PL. Increased feeding amounts of the enriched Artemia yielded positive effects on increased biomass gain, longer average length and decreased length variation coefficient of the PL (P < 0.05). The highest growth performance was from the group fed with the highest amount of the enriched Artemia and comparable to that of the instar-I reference group. The supplement resulted in an evident effect on hypo-salinity tolerance of the PL. PL fed with AL were more tolerant to hypo-salinity than those fed with no AL (P < 0.05). From our standardized swimming test, PL fed only with the enriched Artemia also exhibited no negative-rheotaxis swimming, different from the other groups (P < 0.05). AL had no effect on immunology of the PL when evaluated via Vibrio harveyi challenge, phenoloxidase and superoxide dismutase activities (P > 0.05). These findings suggest benefits of AL on growth performance, increasing hypo-salinity tolerance and swimming strength of shrimp PL.

Performance, insulin sensitivity, carcass characteristics, and fatty acid profile of beef from steers fed microalgae.

Heterotrophic production of microalgae biomass provides a consistent, high-quality source of docosahexaenoic acid (DHA; C22:6 n-3) in triglyceride oils that could be used as a ration supplement for feedlot steers to improve nutritional qualities of beef. Sixty Angus × Simmental steers (438 ± 6.4 kg) were allotted to two treatments (30 steers each, six pens, five steers/pen) to determine the effects of ForPLUS (DHA-rich microalgae Aurantiochytrium limacinum; 63.6% fat; 17.9% DHA; 30 mg/kg Sel-Plex; Alltech Inc.) on performance, insulin sensitivity, LM fatty acid composition, and meat quality. Steers were fed basal diets containing 45% corn, 30% distillers dried grains with solubles, 20% corn silage, and 5% supplement. Basal diets were formulated to contain 16.1% CP and 1.32 Mcal/kg NEg. Treatments were delivered to steers in a ground corn-based top-dress (454 g total/steer) and contained no microalgae for control steers or 100 g/steer daily of ForPLUS for microalgae steers. A glucose tolerance test (GTT) was performed 10 d prior to slaughter. Steers were slaughtered when a target pen BW of 621 kg was achieved. Fatty acid oxidation potential was determined by measuring thiobarbituric acid reactive substances (TBARS) on LM samples collected 24 h after slaughter and aged for 48 h or 21 d. Weight and BW gain did not differ during the study (P ≥ 0.13); however, steers fed microalgae remained in the feedlot seven more days compared to steers fed the control diet (111 vs. 104 d; P = 0.04). Overall DMI decreased (P = 0.002) and G:F increased during the second half of the study (P = 0.04) in steers fed microalgae compared to steers fed the control diet. Steers fed microalgae secreted less insulin (P = 0.01) and took longer to clear glucose (P = 0.01) during a 2-h GTT. Carcass traits did not differ between treatments (P ≥ 0.23). Microalgae had no effect on n-6 content (P = 0.67), but more than doubled the n-3 fatty acid percentage and the n-3:n-6 ratio of the LM (P < 0.0001). The percentage of n-3 fatty acids C20:5 and C22:6 were increased (P < 0.0001) 4-fold and 6.25-fold, respectively, by microalgae supplementation. Concentration of TBARS did not differ in LM aged for 48 h (P = 0.91); however, when aged for 21 d, steers fed microalgae tended to produce LM with greater TBARS concentration compared to steers fed the control diet (P = 0.08). In conclusion, DHA-rich microalgae decreased DMI of steers, and increased n-3 fatty acids and beef oxidation in steaks aged for 21 d.

Visualization of Endoplasmic Reticulum and Mitochondria in Aurantiochytrium limacinum by the Expression of EGFP with Cell Organelle-Specific Targeting/Retaining Signals.

Thraustochytrids are single cell marine eukaryotes that produce large amounts of polyunsaturated fatty acids such as docosahexaenoic acid. In the present study, we report the visualization of endoplasmic reticulum (ER) and mitochondria in a type strain of the thraustochytrid, Aurantiochytrium limacinum ATCC MYA-1381, using the enhanced green fluorescent protein (EGFP) with specific targeting/retaining signals. We expressed the egfp gene with ER targeting/retaining signals from A. limacinum calreticulin or BiP/GRP78 in the thraustochytrid, resulting in the distribution of EGFP signals at the perinuclear region and near lipid droplets. ER-Tracker™ Red, an authentic fluorescent probe for the visualization of ER in mammalian cells, also stained the same region. We observed small lipid droplets generated from the visualized ER in the early growth phase of cell culture. Expression of the egfp gene with the mitochondria targeting signal from A. limacinum cytochrome c oxidase resulted in the localization of EGFP near the plasma membrane. The distribution of EGFP signals coincided with that of MitoTracker® Red CMXRos, which is used to visualize mitochondria in eukaryotes. The ER and mitochondria of A. limacinum were visualized for the first time by EGFP with thraustochytrid cell organelle-specific targeting/retaining signals. These results will contribute to classification of the intracellular localization of proteins expressed in ER and mitochondria as well as analyses of these cell organelles in thraustochytrids.

Dietary supplementation of finishing pigs with the docosahexaenoic acid-rich microalgae, Aurantiochytrium limacinum: effects on performance, carcass characteristics and tissue fatty acid profile.

ObjectiveThe aim of this experiment was to evaluate the effect of dietary supplementation with the docosahexaenoic acid (DHA)-rich microalgae, Aurantiochytrium limacinum (AURA) on pig performance, carcass traits, and the fatty acid composition of pork Longissimus lumborum (LL) and backfat.MethodsA total of 144 Pig Improvement Company (PIC)×Goland finishing pigs (72 females and 72 castrated males) of mean weight 117.1 (±13.1) kg were blocked by sex and body weight and provided with 0% or 1% AURA in isonutritive and isocaloric diets. A total of 24 pens provided 12 replicates per treatment. Animals were weighed on day 0 and 28 with feed and water intake recorded per pen. After 31 days supplementation (28 days of study and 3 days until the slaughtering date) three animals per pen (n = 72) were slaughtered and the LL and backfat thickness, lean meat content and dressing percentage were recorded for the carcasses. The fatty acid (FA) profile of the LL and backfat was established by direct FA methyl ester synthesis.ResultsNo differences were observed for any performance parameters or carcass traits. Supplementation with AURA resulted in significant changes to the FA profiles of both the LL and backfat with male and female pigs responding differently to supplementation in terms of particular FAs. Overall, pork LL samples had significantly higher eicosapentaenoic acid (p<0.001) and DHA concentrations (p<0.001), and higher omega-3 (n-3) FAs (p<0.001), as well as an increased omega3:omega6 (n-3:n-6) ratio (p = 0.001). For backfat, supplementation resulted in significantly higher amounts of DHA (p<0.001) and n-3 FAs (p<0.001).ConclusionThese results indicate that dietary supplementation with 1% AURA over a 31 day period can increase the FA composition of pork LL and backfat, specifically the DHA, with no major impact on growth performance and carcass traits.

Broiler Tissue Enrichment with Docosahexaenoic Acid (DHA) through Dietary Supplementation with &amp;lt;i&amp;gt;Aurantiochytrium limacinum&amp;lt;/i&amp;gt; Algae

The omega-3 fatty acid (n-3 FA) content of broiler tissues can be increased through dietary supplementation of hens with n-3 FA-rich microalgae. The aim of this study was to evaluate the effect of three different dietary inclusion levels of a docosahexaenoic acid (DHA)-rich microalgae (AURA) on broiler performance and the enrichment of tissues with n-3 FA. The randomized study was conducted using 352 birds, housed in 32 pens with 11 birds per pen. Pens were randomly assigned to one of four treatments, with each treatment replicated 8 times. The treatments included one unsupplemented control (0%) and three wheat-soya based experimental diets supplemented with AURA at a level of 0.5%, 1.5% and 2.5% for the starter, grower and finisher periods. Birds were weighed on days 0, 10, 24, 35 and 41, and feed intake was recorded per pen. On day 41, five birds per treatment were euthanized and individually weighed. Thigh muscle, breast muscle, liver, kidney and skin samples were taken post-mortem, freeze dried and DHA content quantified, following fat extraction and methylation, by GC-FID (AOAC 996.06 method). Performance and tissue data were analyzed by ANOVA with Dunnett’s (2-sided) post-hoc test to determine the differences between the mean values for each treatment. Dietary supplementation with AURA had no effect on body weight or feed intake during any period of the study. For thigh muscle, kidney and skin the DHA increased linearly (P < 0.05) with increasing level of dietary AURA, whilst there was a quadratic response in uptake of DHA in breast muscle and liver. The study demonstrated the potential of efficiently enriching broiler meat and organs with DHA by feeding AURA.

Regulation of TG accumulation and lipid droplet morphology by the novel TLDP1 in Aurantiochytrium limacinum F26-b

Thraustochytrids are marine single-cell protists that produce large amounts of PUFAs, such as DHA. They accumulate PUFAs in lipid droplets (LDs), mainly as constituent(s) of triacylglycerol (TG). We identified a novel protein in the LD fraction of Aurantiochytrium limacinum F26-b using 2D-difference gel electrophoresis. The protein clustered with orthologs of thraustochytrids; however, the cluster was evolutionally different from known PAT family proteins or plant LD protein; thus, we named it thraustochytrid-specific LD protein 1 (TLDP1). TLDP1 surrounded LDs when expressed as a GFP-tagged form. Disruption of the tldp1 gene decreased the content of TG and number of LDs per cell; however, irregular and unusually large LDs were generated in tldp1-deficient mutants. Although the level of TG synthesis was unchanged by the disruption of tldp1, the level of TG degradation was higher in tldp1-deficient mutants than in the WT. These phenotypic abnormalities in tldp1-deficient mutants were restored by the expression of tldp1. These results indicate that TLDP1 is a thraustochytrid-specific LD protein and regulates the TG accumulation and LD morphology in A. limacinum F26-b.

The effect of dietary supplementation with Aurantiochytrium limacinum on lactating dairy cows in terms of animal health, productivity and milk composition.

The aim of this study was to investigate the effect of dietary supplementation with the docosahexaenoic acid (DHA)-rich microalgae, Aurantiochytrium limacinum (AURA), on a variety of health and productivity parameters in lactating cows. Twenty-four cows were blocked by parity and number of days in milk and then randomly assigned to a control (CON; n=12) group with no algal supplementation, or a treatment group (AURA; n=12) provided with 100g AURAcow-1 day-1 or 16g DHAcow-1 day-1 . A variety of health and productivity measurements were taken, and results indicated that supplementation had no negative effects on animal health in terms of somatic cell count, haematological and biochemical blood parameters, while body condition was marginally improved by algal supplementation. No differences were found for the various production parameters measured; however, a tendency towards increased milk production was observed for the AURA group during the final stage of the study (+4.5kgcow-1 day-1 , day 78-84). The fatty acid profile of milk was improved by supplementation, with significantly lower saturated fatty acids, significantly higher omega-3 fatty acids and an improved omega-3/omega-6 ratio observed when compared to the control group. The amount of DHA in the milk of cows provided 105g AURAhead-1 day-1 was 4.7mg/100g milk with a peak transfer efficiency from feed to milk at day 49 of 8.3%. These results indicate that supplementation with 105g AURAhead-1 day-1 resulted in the successful enrichment of milk with DHA without negatively impacting the health or productivity of the animals.