Physicochemical parameters of partially hydrolyzed S. salivarius levan fractions

Abstract

SynopsisThe fractions obtained from the partially hydrolyzed branched Streptococcus saliuarius levan were examined in solution. Sedimentation coefficients, So, intrinsic viscosities, [o], weight-average molecular weights, uw, and radii of gyration were obtained from sedimentation velocity, viscosity, and light-scattering measurements. Double logarithmic plots of [o] vs zW and So vs au each yielded two linear segments intersecting at Xw = lo5. Hydrodynamic data suggest that fractions of aw > lo5 behave as compact spheres, whereas for uw < lo5, the particles are best characterized as linear random coils. Calculations based on theories of random coils and spheres support the above observations.

Structural analysis of fructans produced by acetic acid bacteria reveals a relation to hydrocolloid function

“…Moreover, v G values tended to decrease from lower to higher molecular weight fractions (Table 2). This again supports the findings and explanations of Stivala and Zweig (1981) and Kitamura et al (1994) that conformations of both levan and inulin molecules in aqueous solutions strongly depend on their molecular weight. The observed increasing compactness of levan molecules in parallel with their increasing molecular weight (decreasing slope values v G , Table 2) could furthermore be explained by strong intramolecular forces such as hydrogen bonds.…”

“…These results were in agreement with previous findings reporting a spherical molecular shape of levans in aqueous solutions (Arvidson, Rinehart, & GadalaMaria, 2006;Newbrun, Lacy, & Christie, 1971). Molecular-weight dependent conformational changes of levan (Stivala & Zweig, 1981) and inulin molecules (Kitamura et al, 1994) were observed in aqueous solutions, respectively. Polymer chains with molecular weights <10 5 Da exhibited random-coil conformations, whereas molecules with molar masses >10 5 Da adopted globular conformations.…”

Molecular weight dependent structure of the exopolysaccharide levan

“…The conformation of levan has been discussed in earlier studies Benigar et al, 2014;Ehrlich et al, 1975;Jakob et al, 2013;Runyon et al, 2014;S. S. Stivala & Zweig, 1981;Salvatore S. Stivala et al, 1975).…”

“…The radius of gyration was found to be between 20 nm and several hundred nm (Arvidson, Rinehart, & Gadala-Maria, 2006;Jakob et al, 2013;Kasapis, Morris, Gross, & Rudolph, 1994;Runyon et al, 2014), while the hydrodynamic radius ranged between 2.5 nm and 151 nm (Arvidson et al, 2006;Runyon et al, 2014). The unusual low intrinsic viscosity of levan (7 -45 mL/g) indicated a compact and spherical molecular structure (Bae, Oh, Lee, Yoo, & Lee, 2008;Benigar et al, 2014;Ehrlich et al, 1975; S. S. Stivala & Zweig, 1981; Salvatore S. . Studies on the viscosity of levan.…”

Supramolecular Liquid Crystallinity: Spherical Coils of Levan Surrounding Cylindrical Rods of DNA

“…For bacterial levans, the weight-average molecular weight exceeds 10 7 Da [9,10], and there are side chains on up to 30% of the main chain residues [11]. In aqueous solution, levans of molecular weight greater than 10 5 Da behave as compact spheres [12] that show no tendency to self-aggregate [13].…”