Chemistry:Curdlan

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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 initially reported to be produced by "Alcaligenes faecalis var. myxogenes" strain 10C3-K in 1966.[1] This classification for the strain and its descendants is now understood to be inaccurate, giving rise to the new name "Agrobacterium fabrum".[2] The modern industrial strain "A. fabrum" ATCC 31749[lower-alpha 1] had its genome sequenced in 2011.[3] Some sources prefer the open nomenclature Agrobacterium sp.[4]

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. It is also produced by Cellulomonas flavigena, which belongs to a different phylum.[5]

Biosynthesis

Four genes required for curdlan production have been identified in "A. fabrum" ATCC 31749, which produces curdlan in extraordinary amounts, and the closely related A. tumefaciens.[6] A putative operon contains crdS (Q9X2V0, family GT2, Pfam PF13632), encoding β-(1,3)-glucan synthase catalytic subunit,[7] flanked by two additional genes. A separate locus contains a putative regulatory gene, . A membrane-bound phosphatidylserine synthase, encoded by {{not a typo|pss<s y for maximal production of curdlan of high molecular mass. Nitrogen starvation upregulates the curdlan operon and increases the rate of curdlan synthesis.[8]

Applications

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.[9] Its use is being evaluated in fat replacement studies in foodstuffs such as sausages, meat patties and other meat products [10]

See also

References

  1. ↑ ATCC 31749 (KR1) is derived from ATCC 21680 (NTK-u), which is in turn derived from the original mutant K of 10C3. ATCC 31749 gave rise to a mutant ATCC 31750 (KR2).
  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. doi:10.1271/bbb1961.30.764. 
  2. ↑ Du, Yuhui; Zou, Jinrong; Yin, Zhiqiu; Chen, Tingjian (13 April 2023). "Pan-Chromosome and Comparative Analysis of Agrobacterium fabrum Reveal Important Traits Concerning the Genetic Diversity, Evolutionary Dynamics, and Niche Adaptation of the Species". Microbiology Spectrum 11 (2). doi:10.1128/spectrum.02924-22. PMID 36853054. 
  3. ↑ "Agrobacterium fabrum Lassalle et al. ATCC 31749". https://www.atcc.org/products/31749. 
  4. ↑ 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. doi:10.1007/s00253-011-3740-2. PMID 22124723. 
  5. ↑ "Curdlan and other bacterial (1-->3)-beta-D-glucans". Appl Microbiol Biotechnol 68 (2): 163–73. 2005. doi:10.1007/s00253-005-1959-5. PMID 15818477. 
  6. ↑ "Topological characterization of an inner membrane (1-->3)-beta-D-glucan (curdlan) synthase from Agrobacterium sp. strain ATCC31749". Glycobiology 13 (10): 693–706. 2003. doi:10.1093/glycob/cwg093. PMID 12851288. 
  7. ↑ Karnezis, T. (2003-06-10). "Topological characterization of an inner membrane (1->3)- -D-glucan (curdlan) synthase from Agrobacterium sp. strain ATCC31749" (in en). Glycobiology 13 (10): 693–706. doi:10.1093/glycob/cwg093. ISSN 1460-2423. PMID 12851288. 
  8. ↑ "Transcriptome profiling of a curdlan-producing Agrobacterium reveals conserved regulatory mechanisms of exopolysaccharide biosynthesis". Microb Cell Fact 11: 17. February 2012. doi:10.1186/1475-2859-11-17. PMID 22305302. 
  9. ↑ "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)". http://www.fao.org/docrep/X3860E/X3860E12.htm. 
  10. ↑ 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" (in en). Polymer Bulletin 79 (9): 6905–6927. doi:10.1007/s00289-021-03860-1. ISSN 1436-2449. 



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