Curdlan Explained

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.^[1] Subsequently, the taxonomy of this non-pathogenic curdlan-producing bacterium has been reclassified as Agrobacterium species.^[2]

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.^[3] Four genes required for curdlan production have been identified in Agrobacterium sp. ATCC31749, which produces curdlan in extraordinary amounts, and Agrobacterium tumefaciens.^[4] A putative operon contains crdS (Q9X2V0, family GT2,), encoding β-(1,3)-glucan synthase catalytic subunit,^[5] 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.^[6]

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.^[7] Its use is being evaluated in fat replacement studies in foodstuffs such as sausages, meat patties and other meat products ^[8]

See also

• Callose
• Gellan gum

Notes and References

1. Harada T., Fujimori K., Hirose S., Masada M.. 1966. Growth and Glucan (10C3K) Production by a Mutant of Alcaligenes faecalis var myxogenes in Defined Medium. Agric Biol Chem. 30. 764–769. 10.1271/bbb1961.30.764. free.
2. Xiao-Bei Zhan, Chi-Chung Lin, Hong-Tao Zhang. 2012. Recent advances in curdlan biosynthesis, biotechnological production, and applications. Applied Microbiology and Biotechnology. 93. 2. 525–531. 10.1007/s00253-011-3740-2. 22124723. 7185132.
3. McIntosh M, Stone BA, Stanisich VA . Curdlan and other bacterial (1-->3)-beta-D-glucans . Appl Microbiol Biotechnol . 68 . 2 . 163–73 . 2005 . 15818477 . 10.1007/s00253-005-1959-5 . 13123359 .
4. Karnezis T, Epa VC, Stone BA, Stanisich VA . Topological characterization of an inner membrane (1-->3)-beta-D-glucan (curdlan) synthase from Agrobacterium sp. strain ATCC31749 . Glycobiology . 13 . 10 . 693–706 . 2003 . 12851288 . 10.1093/glycob/cwg093 . free .
5. Karnezis. T.. 2003-06-10. Topological characterization of an inner membrane (1->3)- -D-glucan (curdlan) synthase from Agrobacterium sp. strain ATCC31749. Glycobiology. en. 13. 10. 693–706. 10.1093/glycob/cwg093. 12851288 . 1460-2423. free.
6. Ruffing AM, Chen RR . Transcriptome profiling of a curdlan-producing Agrobacterium reveals conserved regulatory mechanisms of exopolysaccharide biosynthesis . Microb Cell Fact . 11 . 17 . February 2012 . 22305302 . 10.1186/1475-2859-11-17 . 3293034 . free .
7. Web site: 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) .
8. Aquinas. Natasha. Bhat M. Ramananda. Selvaraj. Subbalaxmi. 2021-08-25. A review presenting production, characterization, and applications of biopolymer curdlan in food and pharmaceutical sectors. Polymer Bulletin. 79 . 9 . 6905–6927 . en. 10.1007/s00289-021-03860-1. 237299620. 1436-2449. free.