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Viscometric and static light scattering studies on an exopolysaccharide produced by Lactobacillus delbrueckii subspecies bulgaricus NCFB 2483
Author(s) -
Goh Kelvin Kim Tha,
Hemar Yacine,
Singh Harjinder
Publication year - 2004
Publication title -
biopolymers
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.556
H-Index - 125
eISSN - 1097-0282
pISSN - 0006-3525
DOI - 10.1002/bip.20192
Subject(s) - chemistry , molar mass , intrinsic viscosity , multiangle light scattering , random coil , shear thinning , dispersity , viscometer , static light scattering , light scattering , dynamic light scattering , radius of gyration , viscosity , analytical chemistry (journal) , shear rate , rheology , hydrodynamic radius , thermodynamics , chromatography , polymer , scattering , crystallography , polymer chemistry , organic chemistry , materials science , optics , nanotechnology , circular dichroism , physics , nanoparticle , copolymer
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 ∼ 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 × 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 (∼ 1.15) and adopt a random coil conformation. © 2004 Wiley Periodicals, Inc. Biopolymers, 2005