Curdlan is a water-insoluble linear beta-1,3-

glucan A glucan is a polysaccharide derived from D-glucose, linked by glycosidic bonds. Glucans are noted in two forms: alpha glucans and beta glucans. Many beta-glucans are medically important. They represent a drug target for antifungal medications of ...

, a high-molecular-weight polymer of

glucose Glucose is a sugar with the Chemical formula#Molecular formula, molecular formula , which is often abbreviated as Glc. It is overall the most abundant monosaccharide, a subcategory of carbohydrates. It is mainly made by plants and most algae d ...

. Curdlan consists of β-(1,3)-linked glucose residues and forms elastic

gels A gel is a semi-solid that can have properties ranging from soft and weak to hard and tough. Gels are defined as a substantially dilute cross-linked system, which exhibits no flow when in the steady state, although the liquid phase may still ...

upon heating in aqueous suspension. It was reported to be produced by '' Alcaligenes faecalis'' var. ''myxogenes''. Subsequently, the taxonomy of this non-pathogenic curdlan-producing bacterium has been reclassified as ''

Agrobacterium ''Agrobacterium'' is a genus of Gram-negative bacteria established by Harold J. Conn, H. J. Conn that uses horizontal gene transfer to cause tumors in plants. ''Agrobacterium tumefaciens'' is the most commonly studied species in this genus. ''Agr ...

'' species. Extracellular and capsular polysaccharides are produced by a variety of pathogenic and soil-dwelling bacteria. Curdlan is a neutral β-(1,3)-glucan, perhaps with a few intra- or interchain 1,6-linkages, produced as an exopolysaccharide by soil bacteria of the family Rhizobiaceae. Four genes required for curdlan production have been identified in ''

'' sp. ATCC31749, which produces curdlan in extraordinary amounts, and ''

Agrobacterium tumefaciens ''Agrobacterium tumefaciens'' (also known as ''Rhizobium radiobacter'') is the causal agent of crown gall disease (the formation of tumours) in over 140 species of eudicots. It is a rod-shaped, Gram-negative soil bacterium. Symptoms are cause ...

''. A putative

operon In genetics, an operon is a functioning unit of DNA containing a cluster of genes under the control of a single promoter. The genes are transcribed together into an mRNA strand and either translated together in the cytoplasm, or undergo splic ...

contains crdS
Q9X2V0
family GT2, ), encoding β-(1,3)-glucan synthase catalytic subunit, flanked by two additional genes. A separate locus contains a putative regulatory gene, . A membrane-bound phosphatidylserine synthase, encoded by , is also necessary for maximal production of curdlan of high molecular mass. Nitrogen starvation upregulates the curdlan operon and increases the rate of curdlan synthesis. Curdlan has numerous applications as a gelling agent in the food, construction, and pharmaceutical industries and has been approved as a food additive by the U. S. Food and Drug Administration. Its use is being evaluated in fat replacement studies in foodstuffs such as sausages, meat patties and other meat products

References

{{Reflist Polysaccharides

See also

References