Exopolysaccharides are high-molecular-weight polymers that are composed of sugar residues and are secreted by a microorganism
A microorganism or microbe is a microscopic organism that comprises either a single cell , cell clusters, or no cell at all...

 into the surrounding environment. Microorganisms synthesize a wide spectrum of multifunctional polysaccharide
Polysaccharides are long carbohydrate molecules, of repeated monomer units joined together by glycosidic bonds. They range in structure from linear to highly branched. Polysaccharides are often quite heterogeneous, containing slight modifications of the repeating unit. Depending on the structure,...

s including intracellular polysaccharides, structural polysaccharides and extracellular polysaccharides or exopolysaccharides (EPS). Exopolysaccharides generally consist of monosaccharides and some non-carbohydrate substituents (such as acetate
An acetate is a derivative of acetic acid. This term includes salts and esters, as well as the anion found in solution. Most of the approximately 5 billion kilograms of acetic acid produced annually in industry are used in the production of acetates, which usually take the form of polymers. In...

, pyruvate, succinate, and phosphate
A phosphate, an inorganic chemical, is a salt of phosphoric acid. In organic chemistry, a phosphate, or organophosphate, is an ester of phosphoric acid. Organic phosphates are important in biochemistry and biogeochemistry or ecology. Inorganic phosphates are mined to obtain phosphorus for use in...

). Owing to the wide diversity in composition, exopolysaccharides have found multifarious applications in various food and pharmaceutical industries. Many microbial EPS provide properties that are almost identical to the gum
-Natural gums:* Natural gum, any of a number of naturally occurring resinous materials in vegetative species* Gum anima* Gum arabic, used as food additive, adhesive et al.* Cassia gum* Dammar gum* Gellan gum* Guar gum* Kauri gum* Locust bean gum* Spruce gum...

s currently in use. With innovative approaches, efforts are underway to supersede the traditionally used plant and algal gums by their microbial counterparts. Moreover, considerable progress has been made in discovering and developing new microbial EPS that possess novel industrial significance.


The sensory benefits of the exopolysaccharides of lactic acid bacteria are well established and there is evidence for the health properties that are attributable to exopolysaccharides from lactic acid bacteria.

Capsular exopolysaccharides can protect pathogenic bacteria and contribute to their pathogenicity. Attachment of nitrogen-fixing bacteria to plant roots and soil particles, which is important for colonisation of rhizosphere and roots and for infection of the plant, can be mediated by exopolysaccharides. An example for industrial use of exopolysaccharides is the application of dextran in panettone and other breads in the bakery industry. Exopolysaccharides also have an important role in endodontic infections.

List of exopolysaccharides

  • acetan (Acetobacter xylinum)
  • alginate (Azotobacter vinelandii)
  • cellulose
    Cellulose is an organic compound with the formula , a polysaccharide consisting of a linear chain of several hundred to over ten thousand β linked D-glucose units....

     (Acetobacter xylinum)
  • chitosan
    Chitosan is a linear polysaccharide composed of randomly distributed β--linked D-glucosamine and N-acetyl-D-glucosamine...

     (Mucorales spp.)
  • curdlan
    Curdlan is a high molecular weight polymer of glucose. Curdlan consists of β--linked glucose residues and forms elastic gels upon heating in aqueous suspension.It is produced by Agrobacterium biobar, a non pathogenic bacteria....

     (Alcaligenes faecalis var. myxogenes)
  • cyclosophorans (Agrobacterium spp., Rhizobium spp. and Xanthomonas spp.)
  • dextran
    Dextran is a complex, branched glucan composed of chains of varying lengths...

     (Leuconostoc mesenteroides, Leuconostoc dextranicum and Lactobacillus hilgardii)
  • emulsan (Acinetobacter calcoaceticus)
  • galactoglucopolysaccharides (Achromobacter spp., Agrobacterium radiobacter, Pseudomonas marginalis, Rhizobium spp. and Zooglea' spp.)
  • gellan (Aureomonas elodea and Sphingomonas paucimobilis)
  • glucuronan (Sinorhizobium meliloti)
  • N-acetyl-glucosamine (Staphylococcus epidermidis)
  • N-acetyl-heparosan (Escherichia coli)
  • hyaluronic acid (Streptococcus equi)
  • indican
    Indican is a colourless organic compound, soluble in water, naturally occurring in Indigofera plants. It is a precursor of indigo dye.-Chemical reactions:Common and significant reactions involving indican are as follows:...

     (Beijerinckia indica)
  • kefiran
    Kefiran is the clear or pale yellow polysaccharide gel exuded by dairy kefir or water kefir grains.Dairy kefir grains are symbiotic consortia of bacteria and yeasts which ferment milk containing the complex sugar lactose, whereas water kefir grains contain less microbial diversity and can be...

     (Lactobacillus hilgardii)
  • lentinan
    Lentinan is a beta-glucan with a glycosidic β-1,3:β-1,6 linkage. It is an anti-tumor polysaccharide from the shiitake mushroom. Lentinan is a polysaccharide that has a molecular weight of approximately 500,000 Da...

     (Lentinus elodes)
  • levan
    Levan polysaccharide
    Levan, a homopolysaccharide which is composed of D-fructofuranosyl residues joined by 2,6 with multiple branches by 2,1 linkages has great potential as a functional biopolymer in foods, feeds, cosmetics, and the pharmaceutical and chemical industries. Levan can be used as food or a feed additive...

     (Alcaligenes viscosus, Zymomonas mobilis, Bacillus subtilis)
  • pullulan
    Pullulan is a polysaccharide polymer consisting of maltotriose units, also known as α-1,4- ;α-1,6-glucan'. Three glucose units in maltotriose are connected by an α-1,4 glycosidic bond, whereas consecutive maltotriose units are connected to each other by an α-1,6 glycosidic bond...

     (Aureobasidium pullulans)
  • scleroglucan (Sclerotium rolfsii, Sclerotium delfinii and Sclerotium glucanicum)
  • schizophyllan
    Schizophyllan, abbreviated SPG in clinical trial literature, is a neutral extracellular polysaccharide produced by the fungus Schizophyllum commune, consisting of a 1,3-β-D-linked backbone of glucose residues with 1,6-β-D-glucosyl side groups. Schizophyllan is also known as sizofiran.The...

     (Schizophylum commune)
  • stewartan (Pantoea stewartii subsp. stewartii)
  • succinoglycan (Alcaligenes faecalis var myxogenes, Sinorhizobium meliloti
    Sinorhizobium meliloti
    Sinorhizobium meliloti is a Gram-negative nitrogen-fixing bacterium . It forms a symbiotic relationship with legumes from the genera Medicago, Melilotus and Trigonella, including the model legume Medicago truncatula. This symbiosis results in a new plant organ termed a root nodule. The S...

  • xanthan (Xanthomonas campestris)
  • welan (Alcaligenes spp.)

See also

  • Biofilm
    A biofilm is an aggregate of microorganisms in which cells adhere to each other on a surface. These adherent cells are frequently embedded within a self-produced matrix of extracellular polymeric substance...

  • Extracellular polymeric substance
    Extracellular polymeric substance
    Extracellular polymeric substances, also known as exopolysaccharide, or EPS, are high-molecular weight compounds secreted by microorganisms into their environment. These are mostly composed of polysaccharides and can either remain attached to the cell's outer surface, or be secreted into its growth...

  • Polysaccharides
  • Microbiology
    Microbiology is the study of microorganisms, which are defined as any microscopic organism that comprises either a single cell , cell clusters or no cell at all . This includes eukaryotes, such as fungi and protists, and prokaryotes...

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