Selective Fermentation and Prebiotic Index of Sago (Metroxylon sagu) Resistant Starches Type III by Rat Fecal Cultures

Abstract

One of the criteria for prebiotic substance is its selective fermentation by beneficial gut microbes. Previously, sago resistant starch type III (RS3) produced from Metroxylon sagu starch had been proven to resist digestion by gastrointestinal acidity and enzymes. In this research, sago RS3 was evaluated for its selective fermentation and prebiotic potential by fecal cultures. Sago RS3 was incubated with fecal microbial cultures for 72 hours at 37°C and samples were measured for microbial growth, prebiotic index, organic acid concentration and β-glucuronidase activity during the fermentation. Commercial prebiotics FOS (fructooligosaccharides) and inulin were used as comparison. Sago RS3 was selectively fermented by fecal beneficial lactobacilli and bifidobacteria while decreasing the growth of detrimental bacteroides, clostridia and enterobacteria. The prebiotic index of sago RS3, FOS and inulin was +12.19, +9.45 and +6.82, respectively. The butyric acid molar concentration in media with sago RS3 was comparable with FOS and inulin, and low activity of β-glucuronidase was detected in medium with sago RS3. Sago RS3 exhibited prebiotic characteristics comparable with commercial prebiotics and their potential prebiotic function is worth for further in vivo assessment.