In Vitro Fermentation Behavior of Isomalto/Malto-Polysaccharides Using Human Fecal Inoculum Indicates Prebiotic Potential

Scope: This study characterize intestinal fermentation of isomalto/malto-polysaccharides (IMMPs), by monitoring degradation of IMMPs, production of short chain fatty acids (SCFAs), lactic acid, and succinic acid as well as enzyme activity and microbiota composition. Methods and results: IMMP-94 (94% alpha-(1 -> 6) glycosidic linkages), IMMP-96, IMMP-27, and IMMP-dig27 (IMMP-27 after removal of digestible starch segments) are fermented batchwise in vitro using human fecal inoculum. Fermentation digesta samples are taken for analysis in time up till 48h. The fermentation of alpha-(1 -> 6) glycosidic linkages in IMMP-94, IMMP-96, and IMMP-dig27 starts after 12h and finishes within 48h. IMMP-27 fermentation starts directly after inoculation utilizing alpha-(1 -> 4) linked glucosyl residues; however, the utilization of alpha-(1 -> 6) linked glucoses is delayed and start only after the depletion of alpha-(1 -> 4) linked glucose moieties. SCFAs are produced in high amounts with acetic acid and succinic acid being the major products next to propionic acid and butyric acid. The polysaccharide fraction is degraded into isomalto-oligosaccharides (IMOs) mainly by extracellular enzymes. The smaller IMOs are further degraded by cell-associated enzymes. Overall microbial diversity and the relative abundance of Bifidobacterium and Lactobacillus, significantly increase during the fermentation of IMMPs. Conclusion: IMMP containing segments of alpha-(1 -> 6) linked glucose units are slowly fermentable fibers with prebiotic potential.