Low-viscosity α- d-glucan fractions derived from sucrose which are resistant to enzymatic digestion

Abstract

Alternan is the name given to the alternating α(1→3), α(1→6)-linked d-glucan produced from sucrose by the extracellular enzyme system of Leuconostoc mesenteroides NRRL B-1355. The polysaccharide can be produced fermentatively or by cell-free enzyme preparations. Alterman is resistant to hydrolysis by known endoglucanases, and is a poor substrate for most exoglucanases. Although its viscosity is lower than that of commercial dextran, concentrated aqueous solutions (> 12–15% w/v) are still difficult to attain due to high viscosity. Sonication of native alternan lowers its molecular weight from > 10 7 to < 10 6. The sonicated material can be dissolved in water to give solutions of 50% (w/v) or greater. These solutions exhibit rheological properties similar to aqueous solutions of gum arabic. A ‘limit alternan’ produced by hydrolysis with isomaltodextranase has an average molecular weight of approximately 3500, and is rheologically similar to maltodextrins of degree of polymerization (D.P.) approximately 10.