title: Viscometric and static light scattering studies on an exopolysaccharide produced by Lactobacillus delbrueckii subspecies bulgaricus NCFB 2483.
abstract: The rheological properties and molecular parameters of a purified exopolysaccharide (EPS) produced by a ropy strain of Lactobacillus delbrueckii subsp. bulgaricus NCFB 2483 were investigated. Using capillary viscometry, an intrinsic viscosity of 2,013 mL/g was obtained. The flow curves were fitted by both the Carreau and the Cross equations for shear-thinning fluids, with the Carreau equation giving a better fit. The Cross equation fitted fairly well the plot of reduced viscosity as a function of reduced shear rate with an exponent value (1 - n) of approximately 0.76, typical of random coil polymers. Furthermore, the concentration dependence of the viscosity plot showed a gradient of approximately 1.1 in the dilute regime and 3.3 in the semidilute regime. Molecular parameters were obtained using a multiangle laser light scattering technique. The 2483 EPS molecules had a weight-average molar mass of approximately 2 x 10(6) Da and a z-average root mean square radius (RMS) of approximately 151 nm. From the light scattering data, the bacterial EPS was also found to have a low polydispersity index (approximately 1.15) and adopt a random coil conformation.
authors.affiliation: Institute of Food, Nutrition, and Human Health, Massey University, Private Bag 11 222, Palmerston North, New Zealand. K.T.Goh@massey.ac.nz
authors.forename: Kelvin Kim Tha
authors.initials: KK
authors.lastname: Goh
authors.forename: Yacine
authors.initials: Y
authors.lastname: Hemar
authors.forename: Harjinder
authors.initials: H
authors.lastname: Singh
mesh_terms: D002240:Carbohydrate Sequence; D048668:Lactobacillus delbrueckii / Q000737:chemistry* / Q000378:metabolism; D008027:Light; D008970:Molecular Weight; D011135:Polysaccharides, Bacterial / Q000737:chemistry* / Q000302:isolation & purification; D012542:Scattering, Radiation; D014783:Viscosity
chemical_list: D011135:Polysaccharides, Bacterial