In vitro digestion and fecal fermentation behaviors of a pectic polysaccharide from okra (Abelmoschus esculentus) and its impacts on human gut microbiota

This study aimed to understand the in vitro simulated digestion and fecal fermentation behaviors of a pectic polysaccharide from okra (OPP-D) and its impacts on human gut microbiota. Results showed that the content of reducing sugars increased from 0.20 to 0.35 mg/mL during gastric digestion. The molecular weight of OPP-D slightly decreased from 2.242 × 105 to 1.932 × 105 Da during in vitro digestion, and then significantly decreased to 1.269 × 105 Da after in vitro fecal fermentation for 48 h. The apparent viscosity of OPP-D was overall stable during in vitro digestion, but significantly decreased during in vitro fecal fermentation. The constituent monosaccharides of OPP-D, including rhamnose, galacturonic acid, and galactose, were stable during in vitro digestion and fecal fermentation, but their molar ratios were changed from 1: 0.76: 1.82 to 1: 0.74: 2.08 during fecal fermentation for 48 h. The results indicate that OPP-D was partially degraded during in vitro digestion, and was significantly degraded and utilized by human gut microbiota. In addition, some bacteria, such as Bacteroides, Phascolarctobacterium, Megasphaera, and Desulfovibrio, significantly increased after fecal fermentation, suggesting that OPP-D could alter the composition and abundance of human gut microbiota. Moreover, OPP-D could promote the production of short-chain fatty acids during fermentation for 48 h. Especially, acetic acid increased from 11.45 to 19.71 mmol/L, and propionic acid increased from 2.59 to 8.02 mmol/L. In general, this study can be helpful to better understand the potential digestion and fermentation mechanism of OPP-D.