Submitted to: Great Lakes Regional American Chemical Society Symposium
Publication Type: Abstract Only
Publication Acceptance Date: October 20, 2004
Publication Date: October 20, 2004
Citation: Leathers, T.D., Nunnally, M.S., Ahlgren, J.A., Cote, G.L. 2004. Structure and properties of a novel modified alternan [abstract]. 36th Great Lakes Regional American Chemical Society Symposium. October 17-20, 2004. Peoria, Illinois. p. 164. Technical Abstract: Alternan is a branched glucan with a unique backbone structure of alternating alpha-(1-6) and alpha-(1-3) linkages, produced from sucrose by rare strains of the bacterium Leuconostoc mesenteroides. Recently, a simple bioconversion process was described that quantitatively modifies alternan to a form that more closely resembles gum arabic (U.S. Patent 6,479,275). Gum arabic is exclusively imported, and it would be desirable to have a domestic alternative of consistent quality and price. Four strains identified as Penicillium spp. were isolated from soil samples based on their ability to reduce the absorbance at 225 nm of native, high molecular weight alternan. The molar mass and size of native and modified alternan were analyzed by multi-angle light scattering and refractive index during separation by high performance liquid size exclusion chromatography (HPLC SEC-MALS). Native alternan exhibits a high degree of light scattering which is progressively reduced by modification, characteristic of polymer degradation. Concurrent detection by refractive index (RI) shows native alternan as a high molecular weight polymer that is progressively modified to lower molecular weight, heterodisperse forms. Methylation analysis shows that native and modified alternan have similar linkage patterns. The solution viscosity properties of modified alternan resemble those of ultrasonicated alternan and commercial gum arabic, although alternan lacks the emulsification capacity of gum arabic. Alternan solutions are extremely stable at 4-37 deg C and at pH 3-9. Dry preparations of alternan are bright white, tasteless powders that are not highly hygroscopic. Thus, modified alternan is promising for further development as a gum arabic substitute.