title: Physicochemical characterization of an acetan variant secreted by Acetobacter xylinum strain CR1/4.
abstract: Chemical mutagenesis has been used to produce mutants of Acetobacter xylinum NRRL B42 that are cellulose-negative and that produce variants of the acetan structure deficient in the side-chain sugar residues. The product of A. xylinum strain CR1/4 has been shown to possess a tetrasaccharide repeat unit with the side chain terminating in glucuronic acid. X-ray diffraction studies of oriented fibres suggest that the polysaccharide CR1/4 forms a fivefold helix with a pitch of 4.8 nm. Light-scattering studies on CR1/4 solutions suggest a molecular weight of 1.2 x 10(6) with radii of gyration values of 86 nm (aqueous solution) and 67 nm (0.1 M NaCl solution). The magnitude of the measured radii of gyration and the shape of the Holtzer plots suggest that CR1/4 can be described as a stiff coil. Preliminary differential scanning calorimetry data show melting behaviour consistent with order-disorder transitions of a charged helical structure. Rheological studies have revealed new synergistic interactions of CR1/4 with locust bean gum. Comparative studies of acetan and CR1/4 show that decreasing the length of the side chain enhances the solution viscosity.
authors.affiliation: Institute of Food Research, Norwich laboratory, Colney, UK.
authors.forename: M J
authors.initials: MJ
authors.lastname: Ridout
authors.forename: G J
authors.initials: GJ
authors.lastname: Brownsey
authors.forename: V J
authors.initials: VJ
authors.lastname: Morris
authors.forename: P
authors.initials: P
authors.lastname: Cairns
mesh_terms: D002152:Calorimetry, Differential Scanning; D002236:Carbohydrate Conformation; D002240:Carbohydrate Sequence; D055598:Chemical Phenomena; D002627:Chemistry, Physical; D004357:Drug Synergism; D005685:Galactans; D041822:Gluconacetobacter xylinus / Q000737:chemistry* / Q000235:genetics / Q000502:physiology; D008027:Light; D008351:Mannans; D008969:Molecular Sequence Data; D053149:Plant Gums; D011134:Polysaccharides; D011135:Polysaccharides, Bacterial / Q000737:chemistry* / Q000502:physiology; D012542:Scattering, Radiation; D012996:Solutions; D014783:Viscosity; D014867:Water; D014961:X-Ray Diffraction
chemical_list: D005685:Galactans; D008351:Mannans; D053149:Plant Gums; D011134:Polysaccharides; D011135:Polysaccharides, Bacterial; D012996:Solutions; D014867:Water; C068545:acetan; C022901:(1-6)-alpha-glucomannan; C017471:locust bean gum