Abstract: The intestinal flora of the human body is closely related to health. Gut microbiota dysbiosis will lead to intestinal dysfunction and, consequently, a variety of intestinal diseases. In this study, subjects with different diseases were requested to take one of three microecological agents, stachyose, composite probiotics (CPb) and synbiotic MF-13. An Ion Torrent PGM™ sequencing platform was used to analyze the structure of intestinal microflora and the contents of cholesterol and bile acid in the feces of the subjects were measured. Our aim was to investigate the regulatory effect of intervention with microecological agents on the intestinal microflora structure and lipid metabolism. The results showed that 1 067 operational taxonomic units (OUT) were obtained from the fecal microbial samples from all subjects. The dominant bacteria were Firmicutes and Bacteroidetes, altogether accounting for 91.65%, and Bacteroidetes accounting for about 70.10% of the total number of sequences. Bacteroides and Prevotella were the dominant genera, accounting for 33.1% and 33.8% of the total sequences, respectively. At the phylum level, stachyose promoted the proliferation of Bacteroidetes, but inhibited the proliferation of Firmicutes. CPb had no significant effect on the abundance of each phylum, while MF-13 promoted the proliferation of Proteobacteria and Actinobacteria. Stachyose significantly decreased the abundance of Sutterella in subjects with constipation and insomnia, CPb significantly decreased the abundance of Sutterella in subjects with diarrhea, and MF-13 increased the abundance of Parabacteroides. The analysis of intestinal microflora diversity showed that Chao1 index significantly increased during the early period of MF-13 intervention, while there were no significant changes in other diversity indexes. Cluster analysis and non-metric multi-dimensional scaling (NMDS) analysis showed that microecological preparation intervention changed the intestinal microbiota structure in most of the samples, and the microflora structure of all populations showed an overlapping tendency. The intestinal microflora species that significantly differed between individuals were analyzed using Metastat statistics, and it was found that there was no significant change in the abundance of OTUs before and after intervention with each microecological agent, while there was a significant difference between individual subjects. MF-13 significantly promoted the fecal excretion of cholesterol and bile acids (P < 0.05). In conclusion, stachyose has an obvious influence on the intestinal microflora structure of volunteers, while CPb and MF-13 do not. However, MF-13 can increase the intestinal excretion of cholesterol and bile acid, which is beneficial to the metabolism of intestinal cholesterol, but the durability of this effect is poor.

Key words: gut microbiota; microecological agents; high-throughput sequencing technology; cholesterol; bile acids