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Exopolysaccharides are high-molecular-weight polymers that are composed of sugar residues and are secreted by a microorganism into the surrounding environment. Microorganisms synthesize a wide spectrum of multifunctional polysaccharides including intracellular polysaccharides, structural polysaccharides and extracellular polysaccharides or exopolysaccharides (EPS). Exopolysaccharides generally consist of monosaccharides and some non-carbohydrate substituents (such as acetate, pyruvate, succinate, and phosphate). 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 gums 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 as well. 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.
- acetan (Acetobacter xylinum)
- alginate (Azotobacter vinelandii)
- cellulose (Acetobacter xylinum)
- chitosan (Mucorales spp.)
- curdlan (Alcaligenes faecalis var. myxogenes)
- cyclosophorans (Agrobacterium spp., Rhizobium spp. and Xanthomonas spp.)
- dextran (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 (Beijerinckia indica)
- kefiran (Lactobacillus hilgardii)
- lentinan (Lentinus elodes)
- levan (Alcaligenes viscosus, Zymomonas mobilis, Bacillus subtilis)
- pullulan (Aureobasidium pullulans)
- scleroglucan (Sclerotium rolfsii, Sclerotium delfinii and Sclerotium glucanicum)
- schizophyllan (Schizophylum commune)
- stewartan (Pantoea stewartii subsp. stewartii)
- succinoglycan (Alcaligenes faecalis var myxogenes, Sinorhizobium meliloti)
- xanthan (Xanthomonas campestris)
- welan (Alcaligenes spp.)
- Suresh and Mody (2009). "Microbial Exopolysaccharides: Variety and Potential Applications". Microbial Production of Biopolymers and Polymer Precursors. Caister Academic Press. ISBN 978-1-904455-36-3.
- Welman AD (2009). "Exploitation of Exopolysaccharides from lactic acid bacteria". Bacterial Polysaccharides: Current Innovations and Future Trends. Caister Academic Press. ISBN 978-1-904455-45-5.
- Ljungh A, Wadstrom T (editors) (2009). Lactobacillus Molecular Biology: From Genomics to Probiotics. Caister Academic Press. ISBN 978-1-904455-41-7.
- Ullrich M (editor) (2009). Bacterial Polysaccharides: Current Innovations and Future Trends. Caister Academic Press. ISBN 978-1-904455-45-5.