MONIKA MUELLER*, STEFANIE SCHWARZ, HELMUT VIERNSTEIN, RENATE LOEPPERT, WERNER PRAZNIK
*Corresponding author
Department of Pharmaceutical Technology and Biopharmaceutics, University of Vienna, Althanstrasse 14, A-1090 Vienna, Austria

Abstract

Fructans are well known prebiotics; however so far, the influence of branching and degree of polymerization (dp) of the fructan source on the prebiotic effect is not fully elucidated. Growth curves of 14 selected probiotics incubated with unbranched inulin-type (β-2,1-linked) fructan from chicory and branched mixed-type (β-2,1 and β-2,6 linked) fructan from agaves were determined. 13 out of the 14 strains used fructan as sole sugar source. 6 strains used fructan quickly independent of dp and branching, whereas the fermentation behavior of 7 other probiotic strains was dependent on dp and branching. The immediate and long lasting growth enhancement of probiotics is important for the optimal prebiotic effect. As conclusion of our results, this can be fulfilled by combining fructans of different dp ranges. Dependent on the strain, branched or unbranched fructan may be chosen to obtain the most efficient symbiotic supplement.

INTRODUCTION

Fructans as prebiotics have a beneficial effect on human health by selectively stimulating the growth or activity of probiotic bacteria in the colon (1). Regarding the structure, fructans (fructo-oligomers or -polymers) are divided into inulin-type fructan being β-2,1-linked, levan-type fructan being β-2,6-linked or mixed-type fructan being β-2,1- and β-2,6-linked and branched (2). Different plants are used as fructan sources in the functional food industry, including chicory (Cichorium intybus) which contains unbranched inulin-type fructan and agaves (Agave tequilana) which contains fructan with a mixed-type structure and distinct branching characteristic (2, 3).
The structure and degree of polymerization (dp) of fructans have a major impact on the kinetics of fermentation by probiotic bacteria and thus on the beneficial effect of the bacteria on human health.
Inulin-type as well as mixed-type fructans with a lower dp induce the growth of most probiotic strains faster than those with a higher dp. Inulin with longer chains, however, shows a more pronounced, longer lasting prebiotic effect (4-8). Furthermore the dp range of fructans ...