Curdlan

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| CASNo = 54724-00-4

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| UNII = 6930DL209R

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| Formula = (C₆H₁₀O₅)_n

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| Appearance = odourless white powder

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Curdlan is a water-insoluble linear beta-1,3-glucan, a high-molecular-weight polymer of glucose. Curdlan consists of β-(1,3)-linked glucose residues and forms elastic gels upon heating in aqueous suspension. It was reported to be produced by Alcaligenes faecalis var. myxogenes.{{Cite journal|last=Harada T., Fujimori K., Hirose S., Masada M.|date=1966|title=Growth and Glucan (10C3K) Production by a Mutant of Alcaligenes faecalis var myxogenes in Defined Medium|journal=Agric Biol Chem|volume=30|pages=764–769|doi=10.1271/bbb1961.30.764|doi-access=free}} Subsequently, the taxonomy of this non-pathogenic curdlan-producing bacterium has been reclassified as Agrobacterium species.{{Cite journal|last=Xiao-Bei Zhan, Chi-Chung Lin, Hong-Tao Zhang|date=2012|title=Recent advances in curdlan biosynthesis, biotechnological production, and applications|journal=Applied Microbiology and Biotechnology|volume=93|issue=2|pages=525–531|doi=10.1007/s00253-011-3740-2|pmid=22124723|s2cid=7185132}}

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.{{cite journal | vauthors = McIntosh M, Stone BA, Stanisich VA | title = Curdlan and other bacterial (1-->3)-beta-D-glucans | journal = Appl Microbiol Biotechnol | volume = 68 | issue = 2 | pages = 163–73 | year = 2005 | pmid = 15818477 | doi = 10.1007/s00253-005-1959-5 | s2cid = 13123359 }} Four genes required for curdlan production have been identified in Agrobacterium sp. ATCC31749, which produces curdlan in extraordinary amounts, and Agrobacterium tumefaciens.{{cite journal | vauthors = Karnezis T, Epa VC, Stone BA, Stanisich VA | title = Topological characterization of an inner membrane (1-->3)-beta-D-glucan (curdlan) synthase from Agrobacterium sp. strain ATCC31749 | journal = Glycobiology | volume = 13 | issue = 10 | pages = 693–706 | year = 2003 | pmid = 12851288 | doi = 10.1093/glycob/cwg093 | doi-access = free }} A putative operon contains crdS ([https://www.uniprot.org/uniprot/Q9X2V0 Q9X2V0], family GT2, {{Pfam|PF13632}}), encoding β-(1,3)-glucan synthase catalytic subunit,{{Cite journal|last=Karnezis|first=T.|date=2003-06-10|title=Topological characterization of an inner membrane (1->3)- -D-glucan (curdlan) synthase from Agrobacterium sp. strain ATCC31749|journal=Glycobiology|language=en|volume=13|issue=10|pages=693–706|doi=10.1093/glycob/cwg093|pmid=12851288 |issn=1460-2423|doi-access=free}} flanked by two additional genes. A separate locus contains a putative regulatory gene, {{not a typo|crdR}}. A membrane-bound phosphatidylserine synthase, encoded by {{not a typo|pss_AG}}, 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.{{cite journal | vauthors = Ruffing AM, Chen RR | title = Transcriptome profiling of a curdlan-producing Agrobacterium reveals conserved regulatory mechanisms of exopolysaccharide biosynthesis | journal = Microb Cell Fact | volume = 11 | pages = 17 |date=February 2012 | pmid = 22305302 | doi = 10.1186/1475-2859-11-17 | pmc=3293034 | doi-access = free }}

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.{{cite web | title = Compendium of Food Additive Specifications (Addendum 7) Joint FAO/WHO Expert. Curdlan: New specification prepared at the 53rd JECFA (1999) and published in FNP 52 Add 7 (1999) |url=http://www.fao.org/docrep/X3860E/X3860E12.htm}} Its use is being evaluated in fat replacement studies in foodstuffs such as sausages, meat patties and other meat products {{Cite journal|last1=Aquinas|first1=Natasha|last2=Bhat M|first2=Ramananda|last3=Selvaraj|first3=Subbalaxmi|date=2021-08-25|title=A review presenting production, characterization, and applications of biopolymer curdlan in food and pharmaceutical sectors|journal=Polymer Bulletin|volume=79 |issue=9 |pages=6905–6927 |language=en|doi=10.1007/s00289-021-03860-1|s2cid=237299620|issn=1436-2449|doi-access=free}}