Salt Effect on the Antioxidant Activity of Red Microalgal Sulfated Polysaccharides in Soy-Bean Formula

Microalgae's polysaccharides, are they potent antioxidants? Critical review

The scientific community continue to explore novel bioactive molecules by investigating natural origins; microalgae are photosynthetic organisms considered as a sustainable resource to use in many fields. They present a high diversity in species and richness in terms of attractive bio-compounds. The aim of this review is to (1) provide first an overview of current issues related to oxidative stress, and propose a natural metabolite derived from eukaryotic and prokaryotic microalgae; 'polysaccharides' as a powerful antioxidant agent, then, (2) organize the available data on the antioxidant potential of polysaccharides derived from the main microalgal groups (red microalgae, green microalgae, and cyanobacteria) and especially highlighted the key species of each group (Porphyridium sp., Chlorella sp., and Arthrospira sp., respectively), meanwhile, (3) we described the chemical composition of polysaccharides from each class, and (4) we cite briefly the most factors affecting the antioxidant activity of these molecules. Finally, we explored the major challenges and gaps found to require more investigation.

Characterization, antioxidant and anticoagulant properties of exopolysaccharide from marine microalgae

The sulfated exopolysaccharide extracted from marine microalgae attracted considerable attention from both the nutraceutical and pharmaceutical industries. In the present study biomass of five marine microalgae were screened to find strains with high capacity for the production of sulfated exopolysaccharides. The anticoagulant and antioxidant activities of extracted sulfated polysaccharides were evaluated using activated partial thromboplastin time (aPTT), prothrombin time (PT), DPPH and ABTS assays, respectively. The sulfated polysaccharides extracted from Picochlorum sp. showed a strong DPPH scavenging effect with 85% antioxidant activity. The sulfated polysaccharides of Chlorella sorokiniana, Chlorella sp. (L₂) and Chlorella sp. (D₁) scavenged more than 90% of the ABTS radicals. However, the sulfated polysaccharide extracted from Chlorella sorokiniana, and Chlorella sp. (N4) showed anticoagulant properties. The dual anticoagulant-antioxidant activities in Chlorella sorokiniana could be explained by the combination of various factors including sulfate content and their binding site, monosaccharide residue and glycoside bond which are involved in the polysaccharide’s bioactivity.

Sulfated exopolysaccharides (sPS) were extracted from marine green microalgae by the heated acid extraction method.

sPS with the higher sulfate/sugar ratio presented potent ABTS radical scavenging activity.

Some of the sPS revealed anticoagulant effects in activated partial thromboplastin time (aPTT) and prothrombin time (PT) assays.

Advances in microalgal cell wall polysaccharides: a review focused on structure, production, and biological application

Microalgae have been shown to be useful in several biotechnological fields due to their feasible cultivation and high-value biomolecules production. Several substances of interest produced by microalgae, such as: proteins, lipids, and natural colorants, have already been explored. Based on the continuing demand for new natural molecules, microalgae could also be a valuable source of polysaccharides. Polysaccharides are extremely important in aquaculture, cosmetics, pharmaceutical, and food industries, and have great economic impact worldwide. Despite this, reviews on microalgal polysaccharide production, biological activity, and chemical structure are not abundant. Moreover, techniques of microalgal cultivation, coupled with carbohydrate production, need to be clarified in order to develop forward-looking technologies. The present review provides an overview of the main advances in microalgal cell wall polysaccharide production, as well as their associated potential biological applications and chemical structure. Several studies on future prospects, related to microalgae are presented, highlighting the key challenges in microalgal polysaccharide production.

The Antioxidant Activity of Polysaccharides Derived from Marine Organisms: An Overview

Marine-derived antioxidant polysaccharides have aroused extensive attention because of their potential nutritional and therapeutic benefits. However, the comprehensive comparison of identified marine-derived antioxidant polysaccharides is still inaccessible, which would facilitate the discovery of more efficient antioxidants from marine organisms. Thus, this review summarizes the sources, chemical composition, structural characteristics, and antioxidant capacity of marine antioxidant polysaccharides, as well as their protective in vivo effects mediated by antioxidative stress reported in the last few years (2013-2019), and especially highlights the dominant role of marine algae as antioxidant polysaccharide source. In addition, the relationships between the chemical composition and structural characteristics of marine antioxidant polysaccharides with their antioxidant capacity were also discussed. The antioxidant activity was found to be determined by multiple factors, including molecular weight, monosaccharide composition, sulfate position and its degree.

Chemically-Induced Production of Anti-Inflammatory Molecules in Microalgae

Microalgae have been widely recognized as a valuable source of natural, bioactive molecules that can benefit human health. Some molecules of commercial value synthesized by the microalgal metabolism have been proven to display anti-inflammatory activity, including the carotenoids lutein and astaxanthin, the fatty acids EPA (eicosapentaenoic acid) and DHA (docosahexaenoic acid), and sulphated polysaccharides. These molecules can accumulate to a certain extent in a diversity of microalgae species. A production process could become commercially feasible if the productivity is high and the overall production process costs are minimized. The productivity of anti-inflammatory molecules depends on each algal species and the cultivation conditions, the latter being mostly related to nutrient starvation and/or extremes of temperature and/or light intensity. Furthermore, novel bioprocess tools have been reported which might improve the biosynthesis yields and productivity of those target molecules and reduce production costs simultaneously. Such novel tools include the use of chemical triggers or enhancers to improve algal growth and/or accumulation of bioactive molecules, the algal growth in foam and the surfactant-mediated extraction of valuable compounds. Taken together, the recent findings suggest that the combined use of novel bioprocess strategies could improve the technical efficiency and commercial feasibility of valuable microalgal bioproducts production, particularly anti-inflammatory compounds, in large scale processes.

Red alga polysaccharides attenuate angiotensin II-induced inflammation in coronary endothelial cells

The pro-inflammatory vasoconstrictor Angiotensin II can cause endothelial dysfunction and is considered to be one of the mediators of atherosclerosis. Our former results demonstrated that polysaccharides derived from the red alga Porphyridium sp. attenuate inflammatory processes by interfering with tumor necrosis factor-alpha-induced inflammation, in human coronary artery endothelial cells. However, the anti-inflammatory effect of these polysaccharides on inflammation processes occurring under Angiotensin II stimulation is yet unknown. Herein, we studied the polysaccharide's anti-inflammatory effect by quantification of inflammatory markers in Angiotensin II- stimulated Human Coronary Artery Endothelial Cells following pre-treatment with polysaccharides. Inflammatory atherosclerotic pathways up-regulated by Angiotensin II, including adhesion molecule expression and nuclear factor kappa-light-chain-enhancer of activated B cells translocation, were significantly attenuated or diminished in cells pre-treated with the polysaccharides. In addition, the polysaccharides increased the antioxidant response elements activity through the nuclear factor-E2-related factor 2- antioxidant protection system. These polysaccharide's promising abilities may be considered as a basis for future use as a therapeutic agent aimed at improving vascular health by attenuation of the inflammatory atherosclerotic process.

Influence of oxygen on the biosynthesis of polyunsaturated fatty acids in microalgae

As one of the most important environmental factors, oxygen is particularly important for synthesis of n-3 polyunsaturated fatty acids (n-3 PUFA) in microalgae. In general, a higher oxygen supply is beneficial for cell growth but obstructs PUFA synthesis. The generation of reactive oxygen species (ROS) under aerobic conditions, which leads to the peroxidation of lipids and especially PUFA, is an inevitable aspect of life, but is often ignored in fermentation processes. Irritability, microalgal cells are able to activate a number of anti-oxidative defenses, and the lipid profile of many species is reported to be altered under oxidative stress. In this review, the effects of oxygen on the PUFA synthesis, sources of oxidative damage, and anti-oxidative defense systems of microalgae were summarized and discussed. Moreover, this review summarizes the published reports on microalgal biotechnology involving direct/indirect oxygen regulation and new bioreactor designs that enable the improved production of PUFA.

Enhancement of docosahexaenoic acid synthesis by manipulation of antioxidant capacity and prevention of oxidative damage in Schizochytrium sp

Oxygen-mediated cell damage is an important issue in aerobic fermentation. In order to counteract these problems, effect of ascorbic acid on cell growth and docosahexaenoic acid (DHA) production was investigated in Schizochytrium sp. Addition of 9g/L ascorbic acid resulted in 16.16% and 30.44% improvement in cell dry weight (CDW) and DHA yield, respectively. Moreover, the total antioxidant capacity (T-AOC) of cells decreased from 2.17 at 12h to 0 at 60h and did not recover, while ascorbic acid addition could extend the time of arrival zero with the reduced intracellular ROS. However, ROS levels still increased after 72h. Therefore, to further solve the problem of high ROS levels and low T-AOC of cells after 72h, a two-point addition strategy was proposed. With this strategy, DHA yield was further increased to 38.26g/L. This work innovatively investigated the feasibility of manipulating Schizochytrium sp. cultivation through ROS level and T-AOC.