β-1,3 glucan derived from Euglena gracilis and Algamune™ enhances innate immune responses of red drum (Sciaenops ocellatus L.)

Enhancement of systemic virus-specific T lymphocyte responses in pigs supplemented with algae-derived β-glucan

Algae-derived β-glucan has been widely used as a feed additive in the swine industry. The supplementation of β-glucan aims to improve growth performance and modulate the immunity of pigs. However, the potential effects of supplementing β-glucan from algae on immune responses in pigs-specifically antigen-specific immunity-must be determined. In this study, the effects of algae-derived β-glucan supplementation on growth performance, virus neutralising antibody and virus-specific T lymphocytes responses were investigated in pigs. Piglets (n=112 per treatment) were assigned to three treatments including non-supplemented group (control), β-glucan 100 g/ton supplemented group (BG100), and β-glucan 200 g/ton supplemented group (BG200). In this study, production performance of pigs was not found to be different between the experimental groups. Pigs supplemented with β-glucan exhibited high levels of classical swine fever virus (CSFV)-specific producing T lymphocytes and neutralising antibody titer, compared to the control group. Interestingly, supplementation of β-glucan significantly enhanced porcine reproductive and respiratory syndrome virus (PRRSV)-specific interferon-gamma (IFN-γ) producing T lymphocytes, including CD4+, CD8+, and CD4+CD8+ T lymphocyte subpopulations. Moreover, PRRS modified live vaccine (MLV) viremia was reduced in earlier for β-glucan-supplemented pigs compared to the control group. The findings indicate that the algae-derived β-glucan possesses biological potential as an immunomodulatory substance to enhance antiviral immunity, which may contribute to disease resistance in pigs.

Homologous genes shared between probiotics and pathogens affect the adhesion of probiotics and exclusion of pathogens in the gut mucus of shrimp

Clarifying mechanisms underlying the selective adhesion of probiotics and competitive exclusion of pathogens in the intestine is a central theme for shrimp health. Under experimental manipulation of probiotic strain (i.e., Lactiplantibacillus plantarum HC-2) adhesion to the shrimp mucus, this study tested the core hypothesis that homologous genes shared between probiotic and pathogen would affect the adhesion of probiotics and exclusion of pathogens by regulating the membrane proteins of probiotics. Results indicated that the reduction of FtsH protease activity, which significantly correlated with the increase of membrane proteins, could increase the adhesion ability of L. plantarum HC-2 to the mucus. These membrane proteins mainly involved in transport (glycine betaine/carnitine/choline ABC transporter choS, ABC transporter, ATP synthase subunit a atpB, amino acid permease) and regulation of cellular processes (histidine kinase). The genes encoding the membrane proteins were significantly (p < 0.05) up-regulated except those encoding ABC transporters and histidine kinases in L. plantarum HC-2 when co-cultured with Vibrio parahaemolyticus E1, indicating that these genes could help L. plantarum HC-2 to competitively exclude pathogens. Moreover, an arsenal of genes predicted to be involved in carbohydrate metabolism and bacteria-host interactions were identified in L. plantarum HC-2, indicating a clear strain adaption to host's gastrointestinal tract. This study advances our mechanistic understanding of the selective adhesion of probiotics and competitive exclusion of pathogens in the intestine, and has important implications for screening and applying new probiotics for maintaining gut stability and host health.

An Evaluation of Laminarin Additive in the Diets of Juvenile Largemouth Bass (Micropterus salmoides): Growth, Antioxidant Capacity, Immune Response and Intestinal Microbiota

A 28 day feeding trial was conducted to investigate the growth performance, immune response and intestinal microbiota of laminarin (LAM) supplemented diets in juvenile largemouth bass (Micropterus salmoides). Four hundred and eighty fish (initial average weight: 0.72 ± 0.04 g) were randomly divided into four groups (40 fish per tank with three replicates in each group) Four diets were prepared with LAM supplementation at the doses of 0 (control), 5 g Kg^-1 (LL), 10 g Kg^-1 (ML) and 15 g Kg^-1 (HL), respectively. No significant difference in the specific growth rate (SGR) and hepatosomatic index (HSI) was observed in fish among the four groups, or in the lipid and ash content of fish flesh. In addition, fish in the LL group exhibited much higher antioxidant capacity (p < 0.05), while the diets with the inclusion of 5 and 10 g Kg^-1 LAM remarkably decreased the antioxidant capacity of fish (p > 0.05). Dietary LAM at the dose of 5 g Kg^-1 inhibited the transcription of interleukin-1β (il-1β) and tumor necrosis factor-α (tnf-α), while promoting the expression of transforming growth factor-β (tgf-β) in fish intestine. Moreover, the beneficial intestinal bacteria Bacteroide, Comamonas and Mycoplasma abundance significantly increased in fish from the LL group, while the content of opportunistic pathogens Plesiomonas, Aeromonas and Brevinema in fish of the HL group was substantially higher than the control group. Overall, the appropriate dose of supplemented LAM in the diet was 5 g Kg^-1, while an excessive supplementation of LAM in the diet led to microbial community instability in largemouth bass.

Solid-State Fermentation of Plant Feedstuff Mixture Affected the Physiological Responses of European Seabass (Dicentrarchus labrax) Reared at Different Temperatures and Subjected to Salinity Oscillation

This study aimed to evaluate the effects of dietary inclusion of plant feedstuff mixture (PFM) pre-treated by solid-state fermentation (SSF) on the physiological responses of European seabass. For that purpose, two diets were formulated to contain: 20% inclusion level of non-fermented plant ingredients mixture (20Mix) and 20Mix fermented by A. niger in SSF conditions (20Mix-SSF). Seabass juveniles (initial body weight: 20.9 ± 3.3 g) were fed the experimental diets, reared at two different temperatures (21 and 26 °C) and subjected to weekly salinity oscillations for six weeks. Growth performance, digestive enzyme activities, humoral immune parameters, and oxidative stress indicators were evaluated. A reduction in weight gain, feed intake, and thermal growth coefficient was observed in fish fed the fermented diet (20Mix-SSF). Salinity oscillation led to an increase in weight gain, feed efficiency, daily growth index, and thermal growth coefficient, regardless of dietary treatment. Higher rearing temperatures also increased daily growth index. No dietary effect was observed on digestive enzymes activities, whereas rearing temperature and salinity oscillation modulated digestive enzyme activities. Oxidative stress responses were significantly affected by experimental diets, temperature, and salinity conditions. Catalase and glutathione peroxidase activities showed an interactive effect. Fish reared at 21 °C showed higher enzymatic activity when fed the 20Mix-SSF. Conversely, fish reared at 26 °C showed higher GPx activity when fed the 20Mix diet. Fish reared at 26 °C showed reduced peroxidase and lysozyme activities, while salinity fluctuation led to increased lysozyme activity and decreased ACH50 activity. ACH50 activity increased in fish fed the 20Mix-SSF. Overall, the dietary inclusion of PFM fermented by A. niger was unable to mitigate the impact of environmental stress on physiological performance in European seabass. In fact, fermented feed caused an inhibition of growth performances and an alteration of some physiological stress indicators.

Euglena gracilis Promotes Lactobacillus Growth and Antioxidants Accumulation as a Potential Next-Generation Prebiotic

Euglena gracilis, a single-celled microalga with various trophic growth styles under different cultivation conditions, contains nutrients, such as ß-1,3-glucans, essential amino acids, fatty acids, vitamins, and minerals. It has recently attracted attention as a new health food. Among them, ß-1,3-glucans, paramylon of Euglena, is an insoluble dietary fiber and is well known as an immune booster, attenuator of obesity and diabetes, reducer of acute liver injury, and suppressor of atopic dermatitis, and other chronic inflammatory disorders. Recently, evidence has appeared for the positive health effects of foods, food ingredients, or biochemical compounds derived from several other microalgae, such as Chlorella, Spirulina, Dunaliella, Phaeodactylum, and Pavlova. Until most recently, the prebiotic activity of Euglena and paramylon was reported. Emerging prospects of microalgae as prebiotics were well summarized, but the mechanisms behind the bacterial growth promotion by microalgae are not elucidated yet. Thus, we evaluated the prebiotic prospects of both autotrophic and heterotrophic Euglena on six different Lactobacillus. What’s more, the stimulated mechanism was revealed by bacterial culture medium metabolomic analysis. This study could widen the knowledge about the prebiotic activity of Euglena as a next-generation prebiotic and other microalgae-derived compounds as potential health foods.

β-glucan as a promising food additive and immunostimulant in aquaculture industry

The use of antibiotics in aquatic feed reduces the incidence of disease and enhances growth performance, although it presents harmful effects, such as development of resistant bacteria and accumulation in the natural environment. A variety of immune stimulants including probiotics, prebiotics, synbiotics, phytobiotics, organic acids, nucleotides, antioxidants, microalgae, yeast and enzymes have been used in the aquaculture industry. In recent decades, much attention has been paid on finding a variety of immunostimulants with lower cost which also affect specific and non-specific immunity and improve fish resistance against a wide range of pathogens. These stimulants strengthen the fish’s immune system by increasing the number of phagocytes, lysozyme activity and level of immunoglobulin. The use of immune stimulants as an effective tool to overcome diseases and strengthen the immune system of farmed species, leads to the promotion of cellular and humoral defense mechanisms and increases resistance to infectious diseases. Among these immunostimulants used in aquaculture, β-glucans are of particular importance. Glucans are complex polysaccharide compounds extracted from the cell wall of yeasts and fungi. These compounds can stimulate fish growth, survival, and immune function. Therefore, this review discusses the role and importance of β-glucan as a food additive in aquaculture and examines the impact of these compounds on the growth performance, immunity and biochemical parameters of farmed species.

Potential of microalgae as a sustainable feed ingredient for aquaculture

An increase in fish consumption, combined with a decrease in wild fish harvest, is driving the aquaculture industry at rapid pace. Today, farmed seafood accounts for about half of all global seafood demand for human consumption. As the aquaculture industry continues to grow, so does the market for aquafeed. Currently, some of the feed ingredients are coming from low-value forage fishes (fish meal) and terrestrial plants. The production of fish meal can't be increased as it would affect the sustainability and ecosystem of the ocean. Similarly, increasing the production of terrestrial plant-based feed leads to deforestation and increased freshwater use. Hence, alternative and environmentally sustainable sources of feed ingredients need to be developed. Microalgae biomasses represent potential feed source ingredients as the cell metabolites of these microorganisms contain a blend of essential amino acids, healthy triglycerides as fat, vitamins, and pigments. In addition to serving as bulk ingredient in aquafeed, their unique array of bioactive compounds can increase the survivability of farmed species, improve coloration and quality of fillet. Microalgae has the highest areal biomass productivities among photosynthetic organisms, including fodder crops, and thus has a high commercial potential. Also, microalgal production has a low water and arable-land footprint, making microalgal-based feed environmentally sustainable. This review paper will explore the potential of producing microalgae biomass as an ingredient of aquaculture feed.

Emerging prospects of macro- and microalgae as prebiotic

Macro- and microalgae-based foods are becoming popular due to their high nutritious value. The algal biomass is enriched with polysaccharides, protein, polyunsaturated fatty acids, carotenoids, vitamins and minerals. However, the most promising fraction is polysaccharides (PS) or their derivatives (as dietary fibers) which are not entirely fermented by colonic bacteria hence act as potential prebiotic. Primarily, algae become famous as prominent protein sources. Recently, these are widely adopted as functional food (e.g., desserts, dairy products, oil-derivatives, pastas etc.) or animal feed (for poultry, cattle, fish etc.). Besides prebiotic and balanced amino acids source, algae derived compounds implied as therapeutics due to comprising bioactive properties to elicit immunomodulatory, antioxidative, anticancerous, anticoagulant, hepato-protective, and antihypertensive responses. Despite the above potentials, broader research determinations are inevitable to explore these algal compounds until microalgae become a business reality for broader and specific applications in all health domains. However, scale up of algal bioprocess remains a major challenge until commercial affordability is accomplished which can be possible by discovering their hidden potentials and increasing their value and application prospects. This review provides an overview of the significance of algae consumption for several health benefits in humans and animals mainly as prebiotics, however their functional food and animal feed potential are briefly covered. Moreover, their potential to develop an algal-based food industry to meet the people's requirements not only as a sustainable food solution with several health benefits but also as therapeutics is inevitable.

Dietary β-glucan (MacroGard®) improves innate immune responses and disease resistance in Nile tilapia regardless of the administration period

The effects of dietary β-glucan on innate immune responses have been shown in a number of different vertebrate species. However, there is conflicting information about the period of administration (shorter vs. longer), and it is also unclear to what extent β-glucan's effects can be observed post-treatment in fish. Thus, we fed Nile tilapia for 0 (control group; 45 days of control diet), 15 (30 days of control followed by 15 days of β-glucan), 30 (15 days of control followed by 30 days of β-glucan) or 45 days with a diet containing 0.1% of β-glucan (MacroGard®). We evaluated the growth performance at the end of the β-glucan feeding trial and the innate immune function immediately after the feeding trial and 7 and 14 days post-feeding trial. In addition, at day 10 post-feeding trial, we assessed the tilapia's resistance against a bacterial infection. No significant differences were observed in growth performance between the groups; however, fish fed with β-glucan for 30 and 45 days had higher (approx. 8%) relative weight gain compared to the control. Regardless of the administration period, fish fed with β-glucan had higher innate immune responses immediately after the feeding trial such as lysozyme activity in plasma, liver and intestine and respiratory burst compared to the control, and in general these differences were gradually reduced over the withdrawal period (up to 14 days). No differences were observed in the plasma hemolytic activity of the complement or myeloperoxidase activity in plasma or intestine. Moreover, fish from the control group had early mortalities (2 vs. 4-5 days post-infection, respectively) and a lower survival rate (60 vs. 80%, respectively) compared to fish fed with β-glucan for 15 or 30 days, and, interestingly, fish fed for 45 days with β-glucan had no mortality. This study indicates that regardless of the administration period (i.e., 15 up to 45 days), the β-glucan improved the innate immune responses and the tilapia's resistance to disease, and this protection could be observed up to 10 days post-feeding trial, adding in vivo evidence that β-glucan may contribute to a trained innate immunity. Additionally, we showed that a longer period of administration did not cause immunosuppression as previously hypothesized but promoted further growth and immune performance. These findings are relevant to the aquaculture industry and demonstrate that a longer β-glucan feeding protocol may be considered to achieve better results.

Rapid and Accurate Quantification of Paramylon Produced from Euglena gracilis Using an ssDNA Aptamer

The functional ingredients of microalgal biomass are receiving substantial recognition as the global demands for health supplements produced from natural sources are on the rise. Paramylon, a conglomerate of β-1,3-glucans, is one of the major valuable sources derived from Euglena gracilis having multiple applications, thus necessitating the development of an efficient quantification method. Here, we employed a DNA aptamer to quantify the amount of paramylon produced by E. gracilis. Paramylon-specific aptamers were isolated by the systematic evolution of ligands by exponential enrichment (SELEX) process. To evaluate the potential aptamers, the binding affinity between aptamer candidates and paramylon granules was confirmed by a confocal laser scanning microscope and the dissociation constants of the selected aptamers were determined by nonlinear regression analysis. The selected DNA aptamer was successfully used for the quantification of paramylon, and the results were compared to those obtained by the standard methods. The new approach was also used for quantification of paramylon from E. gracilis cells cultured to different cell stages and physiologies. It can be concluded that the aptamer-based protocol for the measurement of paramylon proposed in this study is highly accurate and comparatively less time-consuming.

Use of Ganoderma Lucidum polysaccharide to control cotton fusarium wilt, and the mechanism involved

Induced resistance is an effective measure for controlling plant diseases by utilizing the natural defense of the host and meets the strategic needs of pesticide application and safety for agricultural products worldwide. Ganoderma lucidum polysaccharide (GLP), which is the main active molecule of G. lucidum, has been widely used in functional food and clinical medicine. However, there are few reports of the use of GLP for the prevention and control of plant diseases. The purpose of this study is to explore the effect of GLP and its mechanism of inducing plant resistance. In this study, we found that GLP spray and irrigation root treatments can promote growth in cotton. After soaking in GLP, theseedling height and cotton fusarium wilt resistance both increased to some extent, effects that were dose dependent. After treatment of cotton with GLP, the activities of peroxidase (POD), superoxide dismutase (SOD) and polyphenol oxidase (PPO) in leaves increased significantly, whereas the content of malondialdehyde (MDA) decreased. In addition, QRT-PCR results showed significantly increased relative expression of genes related to the jasmonic acid pathway in cotton. Therefore, we speculate that GLP can induce plant resistance by stimulating the jasmonate pathway.

Potential Industrial Applications and Commercialization of Microalgae in the Functional Food and Feed Industries: A Short Review

Bioactive compounds, e.g., protein, polyunsaturated fatty acids, carotenoids, vitamins and minerals, found in commercial form of microalgal biomass (e.g., powder, flour, liquid, oil, tablet, or capsule forms) may play important roles in functional food (e.g., dairy products, desserts, pastas, oil-derivatives, or supplements) or feed (for cattle, poultry, shellfish, and fish) with favorable outcomes upon human health, including antioxidant, anti-inflammatory, antimicrobial, and antiviral effects, as well as prevention of gastric ulcers, constipation, anemia, diabetes, and hypertension. However, scale up remains a major challenge before commercial competitiveness is attained. Notwithstanding the odds, a few companies have already overcome market constraints, and are successfully selling extracts of microalgae as colorant, or supplement for food and feed industries. Strong scientific evidence of probiotic roles of microalgae in humans is still lacking, while scarce studies have concluded on probiotic activity in marine animals upon ingestion. Limitations in culture harvesting and shelf life extension have indeed constrained commercial viability. There are, however, scattered pieces of evidence that microalgae play prebiotic roles, owing to their richness in oligosaccharides-hardly fermented by other members of the intestinal microbiota, or digested throughout the gastrointestinal tract of humans/animals for that matter. However, consistent applications exist only in the dairy industry and aquaculture. Despite the underlying potential in formulation of functional food/feed, extensive research and development efforts are still required before microalgae at large become a commercial reality in food and feed formulation.

Bioproducts From Euglena gracilis: Synthesis and Applications

In recent years, the versatile phototrophic protist Euglena gracilis has emerged as an interesting candidate for application-driven research and commercialisation, as it is an excellent source of dietary protein, pro(vitamins), lipids, and the β-1,3-glucan paramylon only found in euglenoids. From these, paramylon is already marketed as an immunostimulatory agent in nutraceuticals. Bioproducts from E. gracilis can be produced under various cultivation conditions discussed in this review, and their yields are relatively high when compared with those achieved in microalgal systems. Future challenges include achieving the economy of large-scale cultivation. Recent insights into the complex metabolism of E. gracilis have highlighted unique metabolic pathways, which could provide new leads for product enhancement by genetic modification of the organism. Also, development of molecular tools for strain improvement are emerging rapidly, making E. gracilis a noteworthy challenger for microalgae such as Chlorella spp. and their products currently on the market.

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.

Role of Natural Killer T (NKT) Cells in Type II Diabetes-Induced Vascular Injuries

Background

This study investigated the distribution and features of natural killer T (NKT) cells in the peripheral blood of diabetic patients, and their regulatory roles on vascular endothelial cells.

Material/Methods

Peripheral lymphocytes were isolated from diabetic patients. NKT cell distribution, proportion, and surface and intracellular markers were detected with flow cytometry. Peripheral blood-derived NKT cells were isolated and co-cultured with human umbilical vein endothelial cells (HUVECs). Proliferation and migration of HUVECs were assessed with the CCK-8 assay and the Transwell chamber assay.

Results

The ratios of CD3-CD56+ NK and CD3+CD56+ NKT cells in the peripheral blood of patients with type II diabetes were significantly elevated. The expression levels of NKp30, NKG2D, and NKp44 on the surface were increased in the CD3+CD56+ NKT cells, while the expression levels of NKG2A and 158b were significantly downregulated. The expression level of granzymes in the peripheral blood-derived NKT cells were not changed in patients with type II diabetes, but the expression levels of IFNγ and IL-4 were significantly increased. However, after co-culture with NKT cells derived from the peripheral blood of diabetic patients, the proliferation and migration of HUVECs were significantly inhibited, and was restored by treatment with IL-4 antibody. In addition, the IL-4 stimulus inhibited the proliferation and migration of HUVECs.

Conclusions

Peripheral blood NKT cells are increased and activated in diabetes. NKT cells inhibit the proliferation and migration of HUVECs by secreting IL-4, thereby inducing vascular injuries.

The effect of β-1,3-glucan derived from Euglena gracilis (Algamune™ ) on the innate immunological responses of Nile tilapia (Oreochromis niloticus L.)

Algamune^™ is a commercial additive produced from Euglena gracilis, providing a rich source of the β-1,3-glucan paramylon. Isolated kidney phagocytes of Nile tilapia were incubated with graded doses (0, 8, 16, 32, 64 and 128 μg/ml) of Algamune^™ and purified paramylon to gauge their ability to elicit the production of reactive oxygen species. A linear response was observed for extracellular superoxide anion for both sources but only Algamune^™ for intracellular superoxide anion. After corroborating the immunostimulant properties ex vivo, a feeding trial was conducted to evaluate the dietary supplementation of Algamune^™ (0, 100, 200, 400 and 800 mg/kg of diet) for Nile tilapia. Fish were fed for 3 weeks, after which, fish were sampled for blood and head kidney phagocytes. The remaining fish were challenged with Streptococcus iniae. Macrophage extracellular superoxide anion production was significantly elevated in fish fed diets with 200 mg of Algamune^™ kg^-1 when compared to fish fed the basal diet. Even though the disease challenge did not show statistical differences, it is worth mentioning that fish fed intermediate doses of Algamune^™ had lowest numerical mortality values. Therefore, Algamune^™ was demonstrated to enhance some immunological responses of tilapia both in ex vivo and in vivo.