Abstract: Objective: To evaluate the effect of Lactobacillus paracasei L9 on the content of intestinal short chain fatty acids (SCFAs) in healthy mice. Methods: Fifty three-week-old BALB/c male mice were randomly divided into 5 groups: high dose, medium dose, low dose, positive control and negative control groups. After continuous administration at a dose of 0.2 mL/day per mouse for 21 days, mouse feces were collected, and the cecal contents were also examined after sacrificing the mice on day 21. The changes in SCFAs concentrations of samples were analyzed by gas chromatography, and RTPCR was used to analyze the changes in the intestinal flora. Results: The concentration of short-chain fatty acids including acetic acid, propionic acid and butyric acid increased significantly (P < 0.05), when compared with those observed before administration. The counts of Bifidobaceterium spp. and Lactobacillus and the expression level of butyryl-CoA:acetate CoA-transferase gene (CoAT) were increased significantly (P < 0.05) in feces of mice on day 21. For the cecal contents, Bifidobaceterium spp. count and the expression level of CoAT in low-dose and high-dose groups showed a significant difference (P < 0.05) those in normal saline group. Conclusion: Lactobacillus paracasei L9 can adjust the intestinal flora and promote the production of short chain fatty acids in the intestine of healthy mice. Compared with commercial strain Lactobacillus casei strain Shirota, L9 has a better effect on promoting the yield of propionic acid and butyric acid and hte growth of Bifidobaceterium spp. in the intestine.

Key words: Lactobacillus paracasei L9, short chain fatty acids (SCFAs), intestinal microflora