Characterization, chemical modifications and in vitro anticoagulant properties of an exopolysaccharide produced by Alteromonas infernus

Characterization and biological activities of a novel exopolysaccharide produced from Geobacillus thermodenitrificans HBB 111 strain

In this study, EPS production conditions of Geobacillus thermodenitrificans HBB 111, a thermophilic microorganism, were optimized and the amount of produced EPS (EPS 111) was found to be 44.0 mg/L. EPS 111 was purified using ion exchange chromatography and gel filtration chromatography, and a single type of exopolysaccharide was obtained. The structure of the purified EPS 111 was evaluated by TLC, FTIR, NMR, and GC-MS, and it was observed that it contained hexose (glucose, fructose, galactose and mannose) and pentose sugars. From the SEM photographs, it was understood that EPS 111 had an amorphous, rough, and layered structure. It was found that purified EPS 111 had low cytotoxicity (2.3%) and exhibited high antioxidant activity and remarkable antidiabetic, prebiotic and fibrinolytic activities. It is very valuable that the purified EPS 111 in this study offers multiple biological activities compared to the thermophilic EPSs reported in the literature and has a high potential for use in biotechnological and biomedical fields.

Exploring the Exopolysaccharide Production Potential of Bacterial Strains Isolated from Tunisian Blue Crab Portunus segnis Microbiota

The blue crab (BC) Portunus segnis is considered an invasive species colonizing Tunisian coasts since 2014. This work aims to explore its associated bacteria potential to produce anionic exopolysaccharides (EPSs) in order to open up new ways of valorization. In this study, different BC samples were collected from the coastal area of Sfax, Tunisia. First, bacterial DNA was extracted from seven different fractions (flesh, gills, viscera, carapace scraping water, and three wastewaters from the production plant) and then sequenced using the metabarcoding approach targeting the V3-V4 region of the 16S rDNA to describe their microbiota composition. Metabarcoding data showed that the dominant bacterial genera were mainly Psychrobacter, Vagococcus, and Vibrio. In parallel, plate counting assays were performed on different culture media, and about 250 bacterial strains were isolated and identified by sequencing the 16S rDNA. EPS production by this new bacterial diversity was assessed to identify new compounds of biotechnological interest. The identification of the bacterial strains in the collection confirmed the dominance of Psychrobacter spp. strains. Among them, 43 were identified as EPS producers, as revealed by Stains-all dye in agarose gel electrophoresis. A Buttiauxella strain produced an EPS rich in both neutral sugars including rare sugars such as rhamnose and fucose and uronic acids. This original composition allows us to assume its potential for biotechnological applications and, more particularly, for developing innovative therapeutics. This study highlights bacterial strains associated with BC; they are a new untapped source for discovering innovative bioactive compounds for health and cosmetic applications, such as anionic EPS.

Low-molecular weight sulfated marine polysaccharides: Promising molecules to prevent neurodegeneration in mucopolysaccharidosis IIIA?

Mucopolysaccharidosis IIIA is a hereditary disease caused by mutations in the sulfamidase enzyme that participates in catabolism of heparan sulfate (HS), leading to HS fragment accumulation and multisystemic failure. No cure exists and death occurs around the second decade of life. Two low molecular weight highly sulfated compounds derived from marine diabolican and infernan exopolysaccharides (A5_3 and A5_4, respectively) with heparanase inhibiting properties were tested in a MPSIIIA cell line model, resulting in limited degradation of intracellular HS. Next, we observed the effects of intraperitoneal injections of the diabolican derivative A5_3 from 4 to 12 weeks of age on MPSIIIA mice. Brain metabolism and microstructure, levels of proteins and genes involved in MPSIIIA brain pathophysiology were also investigated. 1H-Magnetic Resonance Spectroscopy (MRS) indicated deficits in energetic metabolism, tissue integrity and neurotransmission at both 4 and 12 weeks in MPSIIIA mice, with partial protective effects of A5_3. Ex-vivo Diffusion Tensor Imaging (DTI) showed white matter microstructural damage in MPSIIIA, with noticeable protective effects of A5_3. Protein and gene expression assessments displayed both pro-inflammatory and pro-apoptotic profiles in MPSIIIA mice, with benefits of A5_3 counteracting neuroinflammation. Overall, derivative A5_3 was well tolerated and was shown to be efficient in preventing brain metabolism failure and inflammation, resulting in preserved brain microstructure in the context of MPSIIIA.

Marine versus Non-Marine Bacterial Exopolysaccharides and Their Skincare Applications

Bacteria are well-known to synthesize high molecular weight polysaccharides excreted in extracellular domain, which constitute their protective microenvironment. Several bacterial exopolysaccharides (EPS) are commercially available for skincare applications in cosmetic products due to their unique structural features, conferring valuable biological and/or textural properties. This review aims to give an overview of bacterial EPS, an important group of macromolecules used in cosmetics as actives and functional ingredients. For this purpose, the main chemical characteristics of EPS are firstly described, followed by the basics of the development of cosmetic ingredients. Then, a focus on EPS production, including upstream and downstream processes, is provided. The diversity of EPS used in the cosmetic industry, and more specifically of marine-derived EPS is highlighted. Marine bacteria isolated from extreme environments are known to produce EPS. However, their production processes are highly challenging due to high or low temperatures; yield must be improved to reach economically viable ingredients. The biological properties of marine-derived EPS are then reviewed, resulting in the highlight of the challenges in this field.

Glycosaminoglycan Mimetics Obtained by Microwave-Assisted Sulfation of Marine Bacterium Sourced Infernan Exopolysaccharide

Sulfated glycosaminoglycans (GAGs) are fundamental constituents of both the cell surface and extracellular matrix. By playing a key role in cell-cell and cell-matrix interactions, GAGs are involved in many physiological and pathological processes. To design GAG mimetics with similar therapeutic potential as the natural ones, the specific structural features, among them sulfate content, sulfation pattern, and chain length, should be considered. In the present study, we describe a sulfation method based on microwave radiation to obtain highly sulfated derivatives as GAG mimetics. The starting low-molecular-weight (LMW) derivative was prepared from the infernan exopolysaccharide, a highly branched naturally slightly sulfated heteropolysaccharide synthesized by the deep-sea hydrothermal vent bacterium Alteromonas infernus. LMW highly sulfated infernan derivatives obtained by conventional heating sulfation have already been shown to display GAG-mimetic properties. Here, the potential of microwave-assisted sulfation versus that of the conventional method to obtain GAG mimetics was explored. Structural analysis by NMR revealed that highly sulfated derivatives from the two methods shared similar structural features, emphasizing that microwave-assisted sulfation with a 12-fold shorter reaction time is as efficient as the classical one.

Evaluation of Bioactive Attributes and Emulsification Potential of Exopolysaccharide Produced by a Brown-rot Fungus Fomitopsis meliae AGDP-2

Mushrooms possess wide array of biologically active secondary metabolites and have been traditionally used for their medicinal properties. Exopolysaccharide (EPS) is one of such bioactive metabolites. The bioactive attributes and emulsification capabilities of the exopolysaccharides produced by a novel brown-rot fungus Fomitopsis meliae AGDP-2 under submerged fermentation has been thoroughly investigated in the present study. Exopolysaccharide displayed anti-oxidant activities in dose dependent manner with the maximum scavenging of ABTS radicals (42.45%), DPPH radicals (75.34%), Hydroxyl radicals (63.64%), Superoxide anion radical (76.54%) and Ferric Reducing Antioxidant Power with IC₅₀ value of 231 µg/mL. Additionally, evaluation of anti-proliferative properties revealed that EPS significantly inhibited the proliferation of HepG2 and HT-29 cancer cells followed by moderate inhibition of HeLa and MCF-7 cancer cell lines and quite less inhibition of L-132 and KB cell lines. The IC₅₀ values of EPS for the abovementioned cell lines are 9.465 µg/mL, 11.25 µg/mL, 38.98 µg/mL, 87.78 µg/mL, 2061 µg/mL and 2361 µg/mL respectively. Moreover EPS also possess good anti-microbial as well as anti-biofilm properties. The studies on emulsification potential described that EPS is good emulsifier of different vegetable oils and the emulsion formed was quite stable up to 144 h.

Bacteria Associated with Benthic Invertebrates from Extreme Marine Environments: Promising but Underexplored Sources of Biotechnologically Relevant Molecules

Microbe–invertebrate associations, commonly occurring in nature, play a fundamental role in the life of symbionts, even in hostile habitats, assuming a key importance for both ecological and evolutionary studies and relevance in biotechnology. Extreme environments have emerged as a new frontier in natural product chemistry in the search for novel chemotypes of microbial origin with significant biological activities. However, to date, the main focus has been microbes from sediment and seawater, whereas those associated with biota have received significantly less attention. This review has been therefore conceived to summarize the main information on invertebrate–bacteria associations that are established in extreme marine environments. After a brief overview of currently known extreme marine environments and their main characteristics, a report on the associations between extremophilic microorganisms and macrobenthic organisms in such hostile habitats is provided. The second part of the review deals with biotechnologically relevant bioactive molecules involved in establishing and maintaining symbiotic associations.

Exopolysaccharides from Marine Microbes: Source, Structure and Application

The unique living environment of marine microorganisms endows them with the potential to produce novel chemical compounds with various biological activities. Among them, the exopolysaccharides produced by marine microbes are an important factor for them to survive in these extreme environments. Up to now, exopolysaccharides from marine microbes, especially from extremophiles, have attracted more and more attention due to their structural complexity, biodegradability, biological activities, and biocompatibility. With the development of culture and separation methods, an increasing number of novel exopolysaccharides are being found and investigated. Here, the source, structure and biological activities of exopolysaccharides, as well as their potential applications in environmental restoration fields of the last decade are summarized, indicating the commercial potential of these versatile EPS in different areas, such as food, cosmetic, and biomedical industries, and also in environmental remediation.

Contributions of Women in Recent Research on Biopolymer Science

Nowadays, biopolymers are playing a fundamental role in our society because of the environmental issues and concerns associated with synthetic polymers. The aim of this Special Issue entitled ‘Women in Polymer Science and Technology: Biopolymers’ is highlighting the work designed and developed by women on biopolymer science and technology. In this context, this short review aims to provide an introduction to this Special Issue by highlighting some recent contributions of women around the world on the particular topic of biopolymer science and technology during the last 20 years. In the first place, it highlights a selection of important works performed on a number of well-studied natural polymers, namely, agar, chitin, chitosan, cellulose, and collagen. Secondly, it gives an insight into the discovery of new polysaccharides and enzymes that have a role in their synthesis and in their degradation. These contributions will be paving the way for the next generation of female and male scientists on this topic.

Three-dimensional structures, dynamics and calcium-mediated interactions of the exopolysaccharide, Infernan, produced by the deep-sea hydrothermal bacterium Alteromonas infernus

The exopolysaccharide Infernan, from the bacterial strain GY785, has a complex repeating unit of nine monosaccharides established on a double-layer of sidechains. A cluster of uronic and sulfated monosaccharides confers to Infernan functional and biological activities. We characterized the 3-dimensional structures and dynamics along Molecular Dynamics trajectories and clustered the conformations in extended two-fold and five-fold helical structures. The electrostatic potential distribution over all the structures revealed negatively charged cavities explored for Ca²⁺ binding through quantum chemistry computation. The transposition of the model of Ca²⁺complexation indicates that the five-fold helices are the most favourable for interactions. The ribbon-like shape of two-fold helices brings neighbouring chains in proximity without steric clashes. The cavity chelating the Ca²⁺ of one chain is completed throughout the interaction of a sulfate group from the neighbouring chain. The resulting is a 'junction zone' based on unique chain-chain interactions governed by a heterotypic binding mode.

Complexation of europium(III) with exopolysaccharides from a marine bacterium envisaged as luminescent probe in a theranostic approach

Exopolysaccharide (EPS) derivatives, produced by Alteromonas infernus bacterium, showed anti-metastatic properties in osteosarcoma (bone tumor). These EPSs could be employed as new drug delivery systems for therapeutic uses. They may represent a new class of ligands to be combined in a theranostic approach with fluorescent metals, such as Eu(III), to serve as imaging probe. The goal of this work was to investigate the feasibility of such coupling by time-resolved laser-induced fluorescence spectroscopy (TRLFS). Since these EPSs are polyelectrolytes their conformation could affect the complexation properties. Thus, viscosimetric measurements were performed as a function of their concentration as well as the background electrolyte concentration. Polysaccharides conformation exhibited a lower hydrodynamic volume for the highest ionic strengths. The resulting random-coiled conformation could affect the complexation with metal for high concentration but no change was evidenced when increasing europium concentration. Two sites of complexation of Eu(III) were evidenced by TRLFS in heparin, whereas only one site was evidenced in two modified EPSs produced from Alteromonas infernus.

Rediscovering bacterial exopolysaccharides of terrestrial and marine origins: novel insights on their distribution, biosynthesis, biotechnological production, and future perspectives

Bacteria exist in colonies as aggregates or associated with surfaces forming biofilms rather than planktonic cells. Living in such a unique manner is always mediated via a matrix of extracellular polymeric substances, which are composed mainly of polysaccharides or specifically exopolysaccharides (EPS). Biofilm formation and hence EPS production are affected by biotic and abiotic factors inducing/inhibiting several involved genes and other molecules. In addition, various aspects of bacterial EPS regarding: physiological functions, molecular weight, and chemical composition were demonstrated. Recent investigations have revealed a wide spectrum of EPS chemical and physicochemical properties showing promising applications in different industrial sectors. For instance, lactic acid bacteria (LAB)- and marine-derived EPS exhibit: immunomodulatory, antioxidant, antitumor, bioremediation of heavy metals, as well as thickening and viscosity modifiers in the food industry. However, bacterial EPS have not yet been commercially implemented, in contrast to plant-derived analogues. The current review aims to rediscover the EPS structural and biosynthetic features derived from marine and terrestrial bacteria, and applications as well.

Antiproliferative Properties of Scandium Exopolysaccharide Complexes on Several Cancer Cell Lines

Antimetastatic properties on both murine and human osteosarcoma cell lines (POS-1 and KHOS) have been evidenced using exopolysaccharide (EPS) derivatives, produced by Alteromonas infernus bacterium. These derivatives had no significant effect on the cell cycle neither a pro-apoptotic effect on osteosarcoma cells. Based on this observation, these EPSs could be employed as new drug delivery systems for therapeutic uses. A theranostic approach, i.e., combination of a predictive biomarker with a therapeutic agent, has been developed notably by combining with true pair of theranostic radionuclides, such as scandium ⁴⁷Sc/⁴⁴Sc. However, it is crucial to ensure that, once complexation is done, the biological properties of the vector remain intact, allowing the molecular tropism of the ligand to recognize its molecular target. It is important to assess if the biological properties of EPS evidenced on osteosarcoma cell lines remain when scandium is complexed to the polymers and can be extended to other cancer cell types. Scandium-EPS complexes were thus tested in vitro on human cell lines: MNNG/HOS osteosarcoma, A375 melanoma, A549 lung adenocarcinoma, U251 glioma, MDA231 breast cancer, and Caco2 colon cancer cells. An xCELLigence Real Cell Time Analysis (RTCA) technology assay was used to monitor for 160 h, the proliferation kinetics of the different cell lines. The tested complexes exhibited an anti-proliferative effect, this effect was more effective compared to EPS alone. This increase of the antiproliferative properties was explained by a change in conformation of EPS complexes due to their polyelectrolyte nature that was induced by complexation. Alterations of both growth factor-receptor signaling, and transmembrane protein interactions could be the principal cause of the antiproliferative effect. These results are very promising and reveal that EPS can be coupled to scandium for improving its biological effects and also suggesting that no major structural modification occurs on the ligand.

Marine Exopolysaccharide Complexed With Scandium Aimed as Theranostic Agents

(1) Background: Exopolysaccharide (EPS) derivatives, produced by Alteromonas infernus bacterium, showed anti-metastatic properties. They may represent a new class of ligands to be combined with theranostic radionuclides, such as ⁴⁷Sc/⁴⁴Sc. The goal of this work was to investigate the feasibility of such coupling. (2) Methods: EPSs, as well as heparin used as a drug reference, were characterized in terms of molar mass and dispersity using Asymmetrical Flow Field-Flow Fractionation coupled to Multi-Angle Light Scattering (AF4-MALS). The intrinsic viscosity of EPSs at different ionic strengths were measured in order to establish the conformation. To determine the stability constants of Sc with EPS and heparin, a Free-ion selective radiotracer extraction (FISRE) method has been used. (3) Results: AF4-MALS showed that radical depolymerization produces monodisperse EPSs, suitable for therapeutic use. EPS conformation exhibited a lower hydrodynamic volume for the highest ionic strengths. The resulting random-coiled conformation could affect the complexation with metal for high concentration. The LogK of Sc-EPS complexes have been determined and showing that they are comparable to the Sc-Hep. (4) Conclusions: EPSs are very promising to be coupled with the theranostic pair of scandium for Nuclear Medicine.

Characterization and Prospective Applications of the Exopolysaccharides Produced by Rhodosporidium babjevae

Purpose: Due to the potential industrial and therapeutic applications of the yeast exopolysaccharides (EPSs), there has been an increasing demand to assess these biopolymers with improved characteristics. This study aimed to characterize the EPSs from Rhodosporidium babjevae (ATCC 90942 and IBRC-M 30088) as well as to evaluate their possible antioxidant, emulsifying and antiproliferative activities. Methods: Rhodosporidium babjevae was cultured for 5 days and following isolation of supernatant, EPSs precipitated with adding of cold absolute ethanol and freeze-dried. The EPSs chemical structure was determined by FT-IR, SEM, HPLC-SEC and GC-MS. Additionally the solubility, water holding capacity and emulsifying activity of EPSs were evaluated. In vitro, antioxidant activity was investigated against DPPH, superoxide and hydroxyl radicals. Finally the EPSs consequence on the cell proliferation of human breast adenocarcinoma (MCF-7) and Madin-Darby canine kidney (MDCK) cell lines was evaluated by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) test. Results: R. babjevae excreted 1.6±0.2 g/L of the EPSs. The EPSs had three fractions with molecular weights of 1.02 ×10⁶ , 5×10⁵ and 2×10⁵ Da. Mannose and glucose were found as the main monosaccharides of the EPSs (84:16 mol%, respectively). The EPSs exhibited emulsifying activity on sun flower oil. The scavenging activities were found to be dose-dependent and higher than hyaluronic acid. Significant difference among the EPSs treatments on the proliferation of MCF-7 and MDCK cell lines was not observed (P>0.05). Conclusion: These results show the interesting potential of the EPSs from R. babjevae as biocompatible compounds for using in food and pharmaceutical fields.

Deep-sea Hydrothermal Vent Bacteria as a Source of Glycosaminoglycan-Mimetic Exopolysaccharides

Bacteria have developed a unique strategy to survive in extreme environmental conditions through the synthesis of an extracellular polymeric matrix conferring upon the cells a protective microenvironment. The main structural component of this complex network constitutes high-molecular weight hydrophilic macromolecules, namely exopolysaccharides (EPS). EPS composition with the presence of particular chemical features may closely be related to the specific conditions in which bacteria evolve. Deep-sea hydrothermal vent bacteria have already been shown to produce EPS rich in hexosamines and uronic acids, frequently bearing some sulfate groups. Such a particular composition ensures interesting functional properties, including biological activities mimicking those known for glycosaminoglycans (GAG). The aim of the present study was to go further into the exploration of the deep-sea hydrothermal vent IFREMER (French Research Institute for Exploitation of the Sea) collection of bacteria to discover new strains able to excrete EPS endowed with GAG-like structural features. After the screening of our whole collection containing 692 strains, 38 bacteria have been selected for EPS production at the laboratory scale. EPS-producing strains were identified according to 16S rDNA phylogeny. Chemical characterization of the obtained EPS highlighted their high chemical diversity with the presence of atypical compositional patterns. These EPS constitute potential bioactives for a number of biomedical applications, including regenerative medicines and cancer treatment.

Psychrophilic lifestyles: mechanisms of adaptation and biotechnological tools

Cold-adapted microorganisms inhabiting permanently low-temperature environments were initially just a biological curiosity but have emerged as rich sources of numerous valuable tools for application in a broad spectrum of innovative technologies. To overcome the multiple challenges inherent to life in their cold habitats, these microorganisms have developed a diverse array of highly sophisticated synergistic adaptations at all levels within their cells: from cell envelope and enzyme adaptation, to cryoprotectant and chaperone production, and novel metabolic capabilities. Basic research has provided valuable insights into how these microorganisms can thrive in their challenging habitat conditions and into the mechanisms of action of the various adaptive features employed, and such insights have served as a foundation for the knowledge-based development of numerous novel biotechnological tools. In this review, we describe the current knowledge of the adaptation strategies of cold-adapted microorganisms and the biotechnological perspectives and commercial tools emerging from this knowledge. Adaptive features and, where possible, applications, in relation to membrane fatty acids, membrane pigments, the cell wall peptidoglycan layer, the lipopolysaccharide component of the outer cell membrane, compatible solutes, antifreeze and ice-nucleating proteins, extracellular polymeric substances, biosurfactants, chaperones, storage materials such as polyhydroxyalkanoates and cyanophycins and metabolic adjustments are presented and discussed.

Marine Polysaccharide-Collagen Coatings on Ti6Al4V Alloy Formed by Self-Assembly

Polysaccharides of marine origin are gaining interest as biomaterial components. Bacteria derived from deep-sea hydrothermal vents can produce sulfated exopolysaccharides (EPS), which can influence cell behavior. The use of such polysaccharides as components of organic, collagen fibril-based coatings on biomaterial surfaces remains unexplored. In this study, collagen fibril coatings enriched with HE800 and GY785 EPS derivatives were deposited on titanium alloy (Ti6Al4V) scaffolds produced by rapid prototyping and subjected to physicochemical and cell biological characterization. Coatings were formed by a self-assembly process whereby polysaccharides were added to acidic collagen molecule solution, followed by neutralization to induced self-assembly of collagen fibrils. Fibril formation resulted in collagen hydrogel formation. Hydrogels formed directly on Ti6Al4V surfaces, and fibrils adsorbed onto the surface. Scanning electron microscopy (SEM) analysis of collagen fibril coatings revealed association of polysaccharides with fibrils. Cell biological characterization revealed good cell adhesion and growth on bare Ti6Al4V surfaces, as well as coatings of collagen fibrils only and collagen fibrils enhanced with HE800 and GY785 EPS derivatives. Hence, the use of both EPS derivatives as coating components is feasible. Further work should focus on cell differentiation.

Marine Microbial-Derived Molecules and Their Potential Use in Cosmeceutical and Cosmetic Products

The oceans encompass a wide range of habitats and environmental conditions, which host a huge microbial biodiversity. The unique characteristics of several marine systems have driven a variety of biological adaptations, leading to the production of a large spectrum of bioactive molecules. Fungi, fungi-like protists (such as thraustochytrids) and bacteria are among the marine organisms with the highest potential of producing bioactive compounds, which can be exploited for several commercial purposes, including cosmetic and cosmeceutical ones. Mycosporines and mycosporine-like amino acids, carotenoids, exopolysaccharides, fatty acids, chitosan and other compounds from these microorganisms might represent a sustainable, low-cost and fast-production alternative to other natural molecules used in photo-protective, anti-aging and skin-whitening products for face, body and hair care. Here, we review the existing knowledge of these compounds produced by marine microorganisms, highlighting the marine habitats where such compounds are preferentially produced and their potential application in cosmetic and cosmeceutical fields.

Exopolysaccharide fraction from Pediococcus pentosaceus KFT18 induces immunostimulatory activity in macrophages and immunosuppressed mice

AIMS

Exopolysaccharide fraction from Pediococcus pentosaceus KFT18 (PE-EPS), a lactic acid bacteria isolated from Kimchi (a Korean fermented vegetable product), was preliminary characterized and its immunostimulating effects were analysed.

METHODS AND RESULTS

In this study, we used interferon-γ (IFN-γ)-primed RAW 264·7 macrophages and CD3/CD28-stimulated splenocytes to determine the immunotimulatory activities of PE-EPS. Upon exposure to PE-EPS, IFN-γ-primed RAW 264·7 macrophages showed significant increases in the expressions of inducible nitric oxide synthase (iNOS), tumour necrosis factor-α (TNF-α), interleukin (IL)-6 and IL-1β. Molecular data using reporter gene assay and electrophoretic mobility shift assay (EMSA) revealed that PE-EPS upregulated transcriptional activity, DNA binding and the nuclear translocation of nuclear factor-κB (NF-κB). Furthermore, PE-EPS enhanced anti-CD3/CD28-specific proliferation and the productions of IL-2 and IFN-γ in primary splenocytes. In cyclophosphamide-induced immunosuppressed mice, pretreatment with PE-EPS (5, 15 or 45 mg kg(-1) day(-1), p.o.) increased thymus and spleen indices, and improved lymphocyte and neutrophil counts.

CONCLUSION

PE-EPS stimulated the IFN-γ-primed macrophages and primary splenocytes to induce immune responses and improved the cyclophosphamide-induced immunosuppression in mice.

SIGNIFICANCE AND IMPACT OF THE STUDY

The results in this study improved our understanding of immunostimulating activity of PE-EPS and supported its potential treatment option as a natural immunostimulant.

Anti-Metastatic Properties of a Marine Bacterial Exopolysaccharide-Based Derivative Designed to Mimic Glycosaminoglycans

Osteosarcoma is the most frequent malignant primary bone tumor characterized by a high potency to form lung metastases. In this study, the effect of three oversulfated low molecular weight marine bacterial exopolysaccharides (OS-EPS) with different molecular weights (4, 8 and 15 kDa) were first evaluated in vitro on human and murine osteosarcoma cell lines. Different biological activities were studied: cell proliferation, cell adhesion and migration, matrix metalloproteinase expression. This in vitro study showed that only the OS-EPS 15 kDa derivative could inhibit the invasiveness of osteosarcoma cells with an inhibition rate close to 90%. Moreover, this derivative was potent to inhibit both migration and invasiveness of osteosarcoma cell lines; had no significant effect on their cell cycle; and increased slightly the expression of MMP-9, and more highly the expression of its physiological specific tissue inhibitor TIMP-1. Then, the in vivo experiments showed that the OS-EPS 15 kDa derivative had no effect on the primary osteosarcoma tumor induced by osteosarcoma cell lines but was very efficient to inhibit the establishment of lung metastases in vivo. These results can help to better understand the mechanisms of GAGs and GAG-like derivatives in the biology of the tumor cells and their interactions with the bone environment to develop new therapeutic strategies.

Characterization and Biotechnological Potential Analysis of a New Exopolysaccharide from the Arctic Marine Bacterium Polaribacter sp. SM1127

Although many kinds of exopolysaccharides (EPSs) from microorganisms have been used in industry, the exploration and utilization of EPSs from polar microorganisms is still rather rare. In this study, a flavobacterial strain, SM1127, from the Arctic brown alga Laminaria, was screened for its high EPS production (2.11 g/l) and was identified as belonging to the genus Polaribacter. The EPS secreted by strain SM1127 has a molecular mass of 220 kDa, and it mainly comprises N-acetyl glucosamine, mannose and glucuronic acid residues bound by heterogeneous linkages. Rheological studies on the aqueous EPS showed that it had a high viscosity and good shear-thinning property. Moreover, the EPS showed a high tolerance to high salinity and a wide pH range. The EPS also had good antioxidant activity. Particularly, its moisture-retention ability was superior to that of any other reported EPS or functional ingredient generally used in cosmetics. The EPS also showed a protective effect on human dermal fibroblasts at low temperature (4 °C). Safety assessment indicated that the EPS is safe for oral administration and external use. These results indicate the promising potential of the EPS from strain SM1127 in the food, cosmetic, pharmaceutical and biomedical fields.

A Direct Sulfation Process of a Marine Polysaccharide in Ionic Liquid

GY785 is an exopolysaccharide produced by a mesophilic bacterial strain Alteromonas infernus discovered in the deep-sea hydrothermal vents. GY785 highly sulfated derivative (GY785 DRS) was previously demonstrated to be a promising molecule driving the efficient mesenchymal stem cell chondrogenesis for cartilage repair. This glycosaminoglycan- (GAG-) like compound was modified in a classical solvent (N,N′-dimethylformamide). However, the use of classical solvents limits the polysaccharide solubility and causes the backbone degradation. In the present study, a one-step efficient sulfation process devoid of side effects (e.g., polysaccharide depolymerization and/or degradation) was developed to produce GAG-like derivatives. The sulfation of GY785 derivative (GY785 DR) was carried out using ionic liquid as a reaction medium. The successful sulfation of this anionic and highly branched heteropolysaccharide performed in ionic liquid would facilitate the production of new molecules of high specificity for biological targets such as tissue engineering or regenerative medicine.

Partial characterization of an extracellular polysaccharide produced by the moderately halophilic bacterium Halomonas xianhensis SUR308

A moderately halophilic bacterium, Halomonas xianhensis SUR308 (Genbank Accession No. KJ933394) was isolated from a multi-pond solar saltern at Surala, Ganjam district, Odisha, India. The isolate produced a significant amount (7.87 g l(-1)) of extracellular polysaccharides (EPS) when grown in malt extract-yeast extract medium supplemented with 2.5% NaCl, 0.5% casein hydrolysate and 3% glucose. The EPS was isolated and purified following the conventional method of precipitation and dialysis. Chromatographic analysis (paper, GC and GC-MS) of the hydrolyzed EPS confirmed its heteropolymeric nature and showed that it is composed mainly of glucose (45.74 mol%), galactose (33.67 mol %) and mannose (17.83 mol%). Fourier-transform infrared spectroscopy indicated the presence of methylene and carboxyl groups as characteristic functional groups. In addition, its proton nuclear magnetic resonance spectrum revealed functional groups specific for extracellular polysaccharides. X-ray diffraction analysis revealed the amorphous nature (CIxrd, 0.56) of the EPS. It was thermostable up to 250 °C and displayed pseudoplastic rheology and remarkable stability against pH and salts. These unique properties of the EPS produced by H. xianhensis indicate its potential to act as an agent for detoxification, emulsification and diverse biological activities.

Exopolysaccharides produced by marine bacteria and their applications as glycosaminoglycan-like molecules

Although polysaccharides are ubiquitous and the most abundant renewable bio-components, their studies, covered by the glycochemistry and glycobiology fields, remain a challenge due to their high molecular diversity and complexity. Polysaccharides are industrially used in food products; human therapeutics fall into a more recent research field and pharmaceutical industry is looking for more and more molecules with enhanced activities. Glycosaminoglycans (GAGs) found in animal tissues play a critical role in cellular physiological and pathological processes as they bind many cellular components. Therefore, they present a great potential for the design and preparation of therapeutic drugs. On the other hand, microorganisms producing exopolysaccharides (EPS) are renewable resources meeting well the actual industrial demand. In particular, the diversity of marine microorganisms is still largely unexplored offering great opportunities to discover high value products such as new molecules and biocatalysts. EPS-producing bacteria from the marine environment will be reviewed with a focus on marine-derived EPS from bacteria isolated from deep-sea hydrothermal vents. Information on chemical and structural features, putative pathways of biosynthesis, novel strategies for chemical and enzymatic modifications and potentialities in the biomedical field will be provided. An integrated approach should be used to increase the basic knowledge on these compounds and their applications; new clean environmentally friendly processes for the production of carbohydrate bioactive compounds should also be proposed for a sustainable industry.

Fermentation technologies for the optimization of marine microbial exopolysaccharide production

In the last decades, research has focused on the capabilities of microbes to secrete exopolysaccharides (EPS), because these polymers differ from the commercial ones derived essentially from plants or algae in their numerous valuable qualities. These biopolymers have emerged as new polymeric materials with novel and unique physical characteristics that have found extensive applications. In marine microorganisms the produced EPS provide an instrument to survive in adverse conditions: They are found to envelope the cells by allowing the entrapment of nutrients or the adhesion to solid substrates. Even if the processes of synthesis and release of exopolysaccharides request high-energy investments for the bacterium, these biopolymers permit resistance under extreme environmental conditions. Marine bacteria like Bacillus, Halomonas, Planococcus, Enterobacter, Alteromonas, Pseudoalteromonas, Vibrio, Rhodococcus, Zoogloea but also Archaea as Haloferax and Thermococcus are here described as EPS producers underlining biopolymer hyperproduction, related fermentation strategies including the effects of the chemical composition of the media, the physical parameters of the growth conditions and the genetic and predicted experimental design tools.

Exopolysaccharides isolated from hydrothermal vent bacteria can modulate the complement system

The complement system is involved in the defence against bacterial infection, or in the elimination of tumour cells. However, disturbances in this system contributes to the pathogenesis of various inflammatory diseases. The efficiency of therapeutic anti-tumour antibodies is enhanced when the complement system is stimulated. In contrast, cancer cells are able to inhibit the complement system and thus proliferate. Some marine molecules are currently being developed as new drugs for use in humans. Among them, known exopolyssacharides (EPSs) generally originate from fungi, but few studies have been performed on bacterial EPSs and even fewer on EPSs extracted from deep-sea hydrothermal vent microbes. For use in humans, these high molecular weight EPSs must be depolymerised. Furthermore, the over-sulphation of EPSs can modify their biological activity. The aim of this study was to investigate the immunodulation of the complement system by either native or over-sulphated low molecular weight EPSs isolated from vent bacteria in order to find pro or anti-activators of complement.

Role of Bacterial Exopolysaccharides (EPS) in the Fate of the Oil Released during the Deepwater Horizon Oil Spill

Halomonas species are recognized for producing exopolysaccharides (EPS) exhibiting amphiphilic properties that allow these macromolecules to interface with hydrophobic substrates, such as hydrocarbons. There remains a paucity of knowledge, however, on the potential of Halomonas EPS to influence the biodegradation of hydrocarbons. In this study, the well-characterized amphiphilic EPS produced by Halomonas species strain TG39 was shown to effectively increase the solubilization of aromatic hydrocarbons and enhance their biodegradation by an indigenous microbial community from oil-contaminated surface waters collected during the active phase of the Deepwater Horizon oil spill. Three Halomonas strains were isolated from the Deepwater Horizon site, all of which produced EPS with excellent emulsifying qualities and shared high (97-100%) 16S rRNA sequence identity with strain TG39 and other EPS-producing Halomonas strains. Analysis of pyrosequence data from surface water samples collected during the spill revealed several distinct Halomonas phylotypes, of which some shared a high sequence identity (≥97%) to strain TG39 and the Gulf spill isolates. Other bacterial groups comprising members with well-characterized EPS-producing qualities, such as Alteromonas, Colwellia and Pseudoalteromonas, were also found enriched in surface waters, suggesting that the total pool of EPS in the Gulf during the spill may have been supplemented by these organisms. Roller bottle incubations with one of the Halomonas isolates from the Deepwater Horizon spill site demonstrated its ability to effectively produce oil aggregates and emulsify the oil. The enrichment of EPS-producing bacteria during the spill coupled with their capacity to produce amphiphilic EPS is likely to have contributed to the ultimate removal of the oil and to the formation of oil aggregates, which were a dominant feature observed in contaminated surface waters.

The potential biotechnological applications of the exopolysaccharide produced by the halophilic bacterium Halomonas almeriensis

We have studied the extracellular polysaccharide (EPS) produced by the type strain, M8(T), of the halophilic bacterium Halomonas almeriensis, to ascertain whether it might have any biotechnological applications. All the cultural parameters tested influenced both bacterial growth and polysaccharide production. EPS production was mainly growth-associated and under optimum environmental and nutritional conditions M8(T) excreted about 1.7 g of EPS per litre of culture medium (about 0.4 g of EPS per gram of dry cell weight). Analysis by anion-exchange chromatography and high-performance size-exclusion chromatography indicated that the exopolysaccharide was composed of two fractions, one of 6.3 × 10(6) and another of 1.5 × 10(4) Daltons. The monosaccharide composition of the high-molecular-weight fraction was mannose (72% w/w), glucose (27.5% w/w) and rhamnose (0.5% w/w). The low-molecular-weight fraction contained mannose (70% w/w) and glucose (30% w/w). The EPS has a substantial protein fraction (1.1% w/w) and was capable of emulsifying several hydrophobic substrates, a capacity presumably related to its protein content. The EPS produced solutions of low viscosity with pseudoplastic behaviour. It also had a high capacity for binding some cations. It contained considerable quantities of sulphates (1.4% w/w), an unusual feature in bacterial polysaccharides. All these characteristics render it potentially useful as a biological agent, bio-detoxifier and emulsifier.

Pharmacological modulation of human mesenchymal stem cell chondrogenesis by a chemically oversulfated polysaccharide of marine origin: potential application to cartilage regenerative medicine

Mesenchymal stem cells (MSCs) are considered as an attractive source of cells for cartilage engineering due to their availability and capacity for expansion and multipotency. Differentiation of MSC into chondrocytes is crucial to successful cartilage regeneration and can be induced by various biological agents, including polysaccharides that participate in many biological processes through interactions with growth factors. Here, we hypothesize that growth factor-induced differentiation of MSC can be increased by chemically oversulfated marine polysaccharides. To test our hypothesis, human adipose tissue-derived MSCs (hATSCs) were cultured in pellets with transforming growth factor (TGF)-β1-supplemented chondrogenic medium containing either the polysaccharide GY785 DR or its oversulfated isoform GY785 DRS. Chondrogenesis was monitored by the measurement of pellet volume, quantification of DNA, collagens, glycosaminoglycans (GAGs), and immunohistological staining. Our data revealed an increase in pellet volume, total collagens, and GAG production with GY785 DRS and chondrogenic medium. The enhanced chondrogenic differentiation of hATSC was further demonstrated by the increased expression of several chondrogenic markers by real-time reverse transcription-polymerase chain reaction. In addition, surface plasmon resonance analyses revealed that TGF-β1 bound GY785 DRS with higher affinity compared to GY785 DR. In association with TGF-β1, GY785 DRS was found to upregulate the phosphorylation of extracellular signal-regulated kinase 1/2, indicating that oversulfated polysaccharide affects the mitogen activated protein kinase signaling activity. These results demonstrate the upregulation of TGF-β1-dependent stem cell chondrogenesis by a chemically oversulfated marine polysaccharide. This polysaccharide of marine origin is easily producible and therefore could be considered a promising additive to drive efficient and reliable MSC chondrogenesis for cartilage tissue engineering.

Heparin-like entities from marine organisms

Polysaccharides are ubiquitous in animals and plant cells where they play a significant role in a number of physiological situations e.g. hydration, mechanical properties of cell walls and ionic regulation. This review concentrates on heparin-like entities from marine procaryotes and eukaryotes. Carbohydrates from marine prokaryotes offer a significant structural chemodiversity with novel material and biological properties. Cyanobacteria are Gram-negative photosynthetic prokaryotes considered as a rich source of novel molecules, and marine bacteria are a rich source of polysaccharides with novel structures, which may be a good starting point from which to synthesise heparinoid molecules. For example, some sulphated polysaccharides have been isolated from gamma-proteobacteria such as Alteromonas and Pseudoalteromonas sp. In contrast to marine bacteria, all marine algae contain sulphated wall polysaccharides, whereas such polymers are not found in terrestrial plants. In their native form, or after chemical modifications, a range of polysaccharides isolated from marine organisms have been described that have anticoagulant, anti-thrombotic, anti-tumour, anti-proliferative, anti-viral or anti-inflammatory activities.In spite of the enormous potential of sulphated oligosaccharides from marine sources, their technical and pharmaceutical usage is still limited because of the high complexity of these molecules. Thus, the production of tailor-made oligo- and polysaccharidic structures by biocatalysis is also a growing field of interest in biotechnology.

An in vitro study of two GAG-like marine polysaccharides incorporated into injectable hydrogels for bone and cartilage tissue engineering

Natural polysaccharides are attractive compounds with which to build scaffolds for bone and cartilage tissue engineering. Here we tested two non-standard ones, HE800 and GY785, for the two-dimensional (2-D) and three-dimensional (3-D) culture of osteoblasts (MC3T3-E1) and chondrocytes (C28/I2). These two glycosaminoglycan-like marine exopolysaccharides were incorporated into an injectable silylated hydroxypropylmethylcellulose-based hydrogel (Si-HPMC) that has already shown its suitability for bone and cartilage tissue engineering. Results showed that, similarly to hyaluronic acid (HA) (the control), HE800 and GY785 significantly improved the mechanical properties of the Si-HPMC hydrogel and induced the attachment of MC3T3-E1 and C28/I2 cells when these were cultured on top of the scaffolds. Si-HPMC hydrogel containing 0.67% HE800 exhibited the highest compressive modulus (11kPa) and allowed the best cell dispersion, especially of MC3T3-E1 cells. However, these cells did not survive when cultured in 3-D within hydrogels containing HE800, in contrast to C28/I2 cells. The latter proliferated in the microenvironment or concentrically depending on the nature of the hydrogel. Among all the constructs tested the Si-HPMC hydrogels containing 0.34% HE800 or 0.67% GY785 or 0.67% HA presented the most interesting features for cartilage tissue engineering applications, since they offered the highest compressive modulus (9.5-11kPa) while supporting the proliferation of chondrocytes.

Effects of a sulfated exopolysaccharide produced by Altermonas infernus on bone biology

The growth and differentiation of bone cells is controlled by various factors, which can be modulated by heparan sulfates. Here, we investigated the effects of an oversulfated exopolysaccharide (OS-EPS) on the bone. We compared the effect of this compound with that of a native EPS. Long-term administration of OS-EPS causes cancellous bone loss in mice due, in part, to an increase in the number of osteoclasts lining the trabecular bone surface. No significant difference in cancellous bone volume was found between EPS-treated mice and age-matched control mice, underlying the importance of sulfation in trabecular bone loss. However, the mechanism sustaining this osteoporosis was unclear. To clarify OS-EPS activities, we investigated the effect of OS-EPS on osteogenesis. Our results demonstrated that OS-EPS inhibited osteoclastogenesis in two cell models. Using the surface plasmon resonance technique, we revealed that OS-EPS can form a hetero-molecular complex OS-EPS/receptor activator of NF-κB ligand (RANKL)/RANK and that RANK had a higher affinity for RANKL pre-incubated with OS-EPS than for RANKL alone, which would be in favor of an increase in bone resorption. However, in vitro, OS-EPS inhibited the early steps of osteoclast precursor adhesion and therefore inhibited the cell fusion step. In addition, we showed that OS-EPS reduced proliferation and accelerated osteoblastic differentiation, leading to strong inhibition of mineralized nodule formation, which would be in favor of an increase in bone resorption. Taken together, these data show different levels of bone resorption regulation by EPSs, most of them leading to proresorptive effects.

Sterilization of exopolysaccharides produced by deep-sea bacteria: impact on their stability and degradation

Polysaccharides are highly heat-sensitive macromolecules, so high temperature treatments are greatly destructive and cause considerable damage, such as a great decrease in both viscosity and molecular weight of the polymer. The technical feasibility of the production of exopolysaccharides by deep-sea bacteria Vibrio diabolicus and Alteromonas infernus was previously demonstrated using a bioproduct manufacturing process. The objective of this study was to determine which sterilization method, other than heat sterilization, was the most appropriate for these marine exopolysaccharides and was in accordance with bioprocess engineering requirements. Chemical sterilization using low-temperature ethylene oxide and a mixture of ionized gases (plasmas) was compared to the sterilization methods using gamma and beta radiations. The changes to both the physical and chemical properties of the sterilized exopolysaccharides were analyzed. The use of ethylene oxide can be recommended for the sterilization of polysaccharides as a weak effect on both rheological and structural properties was observed. This low-temperature gas sterilizing process is very efficient, giving a good Sterility Assurance Level (SAL), and is also well suited to large-scale compound manufacturing in the pharmaceutical industry.

An exopolysaccharide produced by the novel halophilic bacterium Halomonas stenophila strain B100 selectively induces apoptosis in human T leukaemia cells

Microbial exopolysaccharides (EPSs) are highly heterogeneous polymers produced by fungi and bacteria and have recently been attracting considerable attention from biotechnologists because of their potential applications in many fields, including biomedicine. We have screened the antitumoural activity of a panel of sulphated EPSs produced by a newly discovered species of halophilic bacteria. We found that the novel halophilic bacterium Halomonas stenophila strain B100 produced a heteropolysaccharide that, when oversulphated, exerted antitumoural activity on T cell lines deriving from acute lymphoblastic leukaemia (ALL). Only tumour cells were susceptible to apoptosis induced by the sulphated EPS (B100S), whilst primary T cells were resistant. Moreover, freshly isolated primary cells from the blood of patients with ALL were also susceptible to B100S-induced apoptosis. The newly discovered B100S is therefore the first bacterial EPS that has been demonstrated to exert a potent and selective pro-apoptotic effect on T leukaemia cells, and thus, we propose that the search for new antineoplastic drugs should include the screening of other bacterial EPSs, particularly those isolated from halophiles.