Bacterial, short-chain fatty acid and gas profiles of partially hydrolyzed guar gum in vitro fermentation by human fecal microbiota

Carbohydrates with different structures have metabolic differences in the human body, as well as individual differences. The present study aimed to investigate the effects of bacterial, short-chain fatty acids (SCFAs) and gas profiles of partially hydrolyzed guar gum (PHGG) on the fecal microbiota of 41 Chinese individuals by simulated fermentation in vitro. Results showed that PHGG stimulated the growth of Bifidobacterium and Faecalibacterium, inhibited the growth of Escherichia-Shigella, Klebsiella, and Dorea, and induced the production of fermentation gases (CO2, and H2) and SCFAs (acetic acid, butyric acid). Furthermore, Bifidobacterium was significantly increased in the young female and the old male-originated samples, while Klebsiella was significantly decreased in the old female ones after PHGG intervention, and there were also certain differences in gases and SCFAs among different population samples. These findings indicate that PHGG can modulate gut microbiota and metabolism well, whereas its use varies in different populations.

Lactobacillus johnsonii alleviates colitis by TLR1/2-STAT3 mediated CD206+ macrophagesIL-10 activation

Imbalance of gut microbiota homeostasis is related to the occurrence of ulcerative colitis (UC), and probiotics are thought to modulate immune microenvironment and repair barrier function. Here, in order to reveal the interaction between UC and gut microbiota, we screened a new probiotic strain by 16S rRNA sequencing from Dextran Sulfate Sodium (DSS)-induced colitis mice, and explored the mechanism and clinical relevance. Lactobacillus johnsonii (L. johnsonii), as a potential anti-inflammatory bacterium was decreased colonization in colitis mice. Gavage L. johnsonii could alleviate colitis by specifically increasing the proportion of intestinal macrophages and the secretion of Il-10 with macrophages depleted model and in Il10^-/- mice. We identified this subset of immune cells activated by L. johnsonii as CD206⁺ macrophages^IL-10. Mechanistically, L. johnsonii supplementation enhanced the mobilization of CD206⁺ macrophages^IL-10 through the activation of STAT3 in vivo and in vitro. In addition, we revealed that TLR1/2 was essential for the activation of STAT3 and the recognition of L. johnsonii by macrophages. Clinically, there was positive correlation between the abundance of L. johnsonii and the expression level of MRC1, IL10 and TLR1/2 in UC tissues. L. johnsonii could activate native macrophages into CD206⁺ macrophages and release IL-10 through TLR1/2-STAT3 pathway to relieve experimental colitis. L. johnsonii may serve as an immunomodulator and anti-inflammatory therapeutic target for UC.

[Effects of different carbohydrates on the simulation of human intestinal bacterial flora with in vitro culture]

OBJECTIVE

To investigate the optimal growth condition of human fecal bacterial flora in vitro by comparing the effect of different carbohydrates as cultural media.

METHODS

Three fecal samples (1, 2, 3) were collected and inoculated into a single-stage chemostat system, in which starch medium (VI) and starch polysaccharide medium(XP) were used. Samples were collected for bacterial genomic DNA extraction and polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) analysis. Bacterial composition and short chain fatty acid (SCFA) were then analyzed.

RESULTS

The single stage chemostat system reached steady after operating 8 days, when evaluated by the PCR-DGGE. Bacterial 16s rRNA high-throughput sequencing showed that the intestinal bacteria of these three volunteers was mainly composed of four bacterial phyla, namely, Bacteroidetes, Firmicutes, Proteobacteria and Actinobacteria. When the influence of bacterial abundance was considered, the similarity of bacterial composition between the original fecal samples to the harvested flora after culture was 0.847, 0.825, 0.968 in VI medium and 0.927, 0.926, 0.836 in XP medium, respectively. The similarity was decreased to 0.553, 0.580, 0.623 with VI medium and 0.617, 0.520, 0.574 with XP medium, when the number of bacterial species was considered. The variation of host individual also influenced the simulation. VI medium favored fecal sample 3, while XP medium more benefited sample 1 and 2. Bacteroides and Lachnospiraceae_incertae_sedis grew in both VI and XP medium. However, some species were only detected in VI medium and some were specifically found in the XP medium. The SCFA concentration in fermenters was 15-35 mmol/L, mainly propionate and butyrate.

CONCLUSIONS

The chemostat system works for stimulating human gut bacterial flora in vitro. The bacterial composition is affected by different carbohydrate in the culture medium yet with close simulation higher than 80%.