Effects of NatureKnit™, a Blend of Fruit and Vegetable Fibers Rich in Naturally Occurring Bound Polyphenols, on the Metabolic Activity and Community Composition of the Human Gut Microbiome Using the M-SHIME® Gastrointestinal Model

Abstract

This study evaluated the impact of a proprietary blend of fruit and vegetable fibers rich in naturally occurring bound polyphenols (commercially marketed as NatureKnit^TM), compared to purified fibers (inulin and psyllium), on the human gut microbiome using the validated M-SHIME^® gastrointestinal model. A short-term single-stage colonic M-SHIME^® experiment (with fecal inoculum from three healthy human donors) was used to evaluate the test products compared to a negative control. Samples were assessed for pH, gas pressure, short-chain fatty acid (SCFA) production, lactate, and ammonium from 0 h to 48 h. Microbial community composition was assessed at 0 h (negative control only), 24 h, and 48 h (lumen) or 48 h (mucosal). All test products were fermented well in the colon as demonstrated by decreases in pH and increases in gas pressure over time; these changes occurred faster with the purified fibers, whereas NatureKnit™ demonstrated slow, steady changes, potentially indicating a gentler fermentation process. SCFA production significantly increased over the course of the 48 h experiment with all test products versus negative control. SCFA production was significantly greater with NatureKnit™ versus the purified fibers. Shifts in the microbial community composition were observed with all test products versus negative control. At the conclusion of the 48 h experiment, the absolute bacterial abundance and the richness of observed bacterial taxa in the lumen compartment was significantly greater with NatureKnit™ compared with inulin, psyllium, and negative control. Overall, NatureKnit™ demonstrated greater or similar prebiotic effects on study measures compared with established prebiotic fibers.

Keywords: Mucosal Simulator of the Human Intestinal Microbial Ecosystem (M-SHIME®); bound polyphenols; fiber; gut microbiome; inulin; polyphenol; prebiotic; psyllium; short-chain fatty acid (SCFA).

Figure 1

Changes in (a) pH and (b) gas pressure over time following test product administration in M-SHIME^® short-term colonic incubations. Incubations included the negative control (colonic incubation blank medium), NatureKnit™ (1.667 g fiber/L, 3.333 g/L total), inulin (1.667 g fiber/L), and psyllium (1.667 g fiber/L). Donors A, B, and C represent three individual healthy human fecal donors, and average donor represents the average of the three donors. Incubations were performed in triplicate (n = 3) and the results are presented as mean ± standard deviation. Statistical analysis was performed over the course of the entire colonic incubation phase (i.e., between 0 h and 48 h). Paired student’s t-tests were used to compare changes observed for the test products versus negative control. A p-value of <0.05 was considered statistically significant. Different letters above the bars indicate statistically significant differences between test conditions, while no significant differences were observed between test conditions that share the same letter. M-SHIME^® = Mucosal Simulator of the Human Intestinal Microbial Ecosystem.

Figure 2

Changes in (a) total SCFA, (b) lactate, (c) branched SCFA, and (d) ammonium-N over time following test product administration in M-SHIME^® short-term colonic incubations. Incubations included the negative control (colonic incubation blank medium), NatureKnit™ (1.667 g fiber/L, 3.333 g/L total), inulin (1.667 g fiber/L), and psyllium (1.667 g fiber/L). Donors A, B, and C represent three individual healthy human fecal donors, and average donor represents the average of the three donors. Incubations were performed in triplicate (n = 3) and the results are presented as mean ± standard deviation. Statistical analysis was performed over the course of the entire colonic incubation phase (i.e., between 0 h and 48 h) or over the course of the initial time interval (i.e., between 0 h and 6 h; lactate only). Paired student’s t-tests were used to compare changes observed for the test products versus negative control. A p-value of <0.05 was considered statistically significant. Different letters above the bars indicate statistically significant differences between test conditions, while no significant differences were observed between test conditions that share the same letter. M-SHIME^® = Mucosal Simulator of the Human Intestinal Microbial Ecosystem; SCFA = short chain fatty acid.

Figure 2

Changes in (a) total SCFA, (b) lactate, (c) branched SCFA, and (d) ammonium-N over time following test product administration in M-SHIME^® short-term colonic incubations. Incubations included the negative control (colonic incubation blank medium), NatureKnit™ (1.667 g fiber/L, 3.333 g/L total), inulin (1.667 g fiber/L), and psyllium (1.667 g fiber/L). Donors A, B, and C represent three individual healthy human fecal donors, and average donor represents the average of the three donors. Incubations were performed in triplicate (n = 3) and the results are presented as mean ± standard deviation. Statistical analysis was performed over the course of the entire colonic incubation phase (i.e., between 0 h and 48 h) or over the course of the initial time interval (i.e., between 0 h and 6 h; lactate only). Paired student’s t-tests were used to compare changes observed for the test products versus negative control. A p-value of <0.05 was considered statistically significant. Different letters above the bars indicate statistically significant differences between test conditions, while no significant differences were observed between test conditions that share the same letter. M-SHIME^® = Mucosal Simulator of the Human Intestinal Microbial Ecosystem; SCFA = short chain fatty acid.

Figure 3

Stacked bar plots showing (a) absolute phyla abundances (cells/mL) in the lumen compartment and (b) relative phyla abundances in the mucosal compartment. Incubations included the negative control (colonic incubation blank medium), NatureKnit™ (1.667 g fiber/L, 3.333 g/L total), inulin (1.667 g fiber/L), and psyllium (1.667 g fiber/L). Donors A, B, and C represent three individual healthy human fecal donors. Incubations were performed in triplicate (n = 3). Flow cytometry was used to determine the total number of bacterial cells in the luminal samples.

Figure 4

Jitter plots showing (a) the absolute abundance (cells/mL) of the top 20 most abundant phyla and families in the lumen compartment after 24 h, (b) the absolute abundance (cells/mL) of the top 20 most abundant phyla and families in the lumen compartment after 48 h, and (c) the relative abundance of the top 20 most abundant phyla and families in the mucosal compartment after 48 h. Incubations included the negative control (colonic incubation blank medium), NatureKnit™ (1.667 g fiber/L, 3.333 g/L total), inulin (1.667 g fiber/L), and psyllium (1.667 g fiber/L). Incubations were performed for each donor in triplicate (per donor, n = 3; total, n = 9). Each dot represents the average across donors.

Figure 5

Effect of the test products on alpha diversity as calculated by the observed taxa, Shannon, and inverse Simpson indexes in the (a) lumen compartment (24 h and 48 h) and (b) mucosal compartment (48 h). Incubations included the negative control (colonic incubation blank medium), NatureKnit™ (1.667 g fiber/L, 3.333 g/L total), inulin (1.667 g fiber/L), and psyllium (1.667 g fiber/L). Donors A, B, and C represent three individual healthy human fecal donors. Incubations were performed in triplicate (n = 3). Paired student’s t-tests were used to compare each test product with the negative control. A p-value of <0.05 was considered statistically significant; the asterisk represents a significant difference versus negative control.