Dairy propionibacteria from milk or cheese diets remain viable and enhance propionic acid production in the mouse cecum

The supply of carbohydrates is a growth-limiting factor for the intestinal microflora which ferments non-digested or incompletely digested carbohydrates, rendering short-chain fatty acids (SCFA) as major products. These organic acids are involved in a wide range of physiological functions. Therefore, it is of great interest to increase the SCFA intestinal production by using probiotic strains. The aim of this study was to assess in vitro and in vivo the contribution of four strains of propionibacteria to the production of SCFA and lactic acid in the mouse cecum, and to determine the viability and metabolic activity of propionibacteria in the cecum after feeding mice with a small Swiss-type cheese elaborated with P. acidipropionici CRL 1198. The bacterial count and total amount of SCFA, and the molar ratios of each acid and lactic acid concentration, were determined in the cecal content of mice after 7 d of feeding with milk containing different dairy propionibacteria (PAB). The same determinations were performed after in vitro lactose, sucrose or fructooligosaccharide fermentation in cecal homogenates inoculated with propionibacteria. Viability, adhesion to the intestinal mucosa and bacterial beta-galactosidase activity were also compared in mice fed with milk or cheese containing P. acidipropionici CRL 1198 in a daily dose of 10(9) bacteria. In our experiments, a milk and PAB feeding and lactose fermentation in the cecal content inoculated with PAB led to a higher production of propionic acid. In most cases propionibacteria increased propionic acid production at the expense of the butyric acid produced by the intestinal microflora. P. acidipropionici CRL 1198 maintained its adhesive property, viability and metabolic activity in the cecum of mice fed with a cheese diet. These results suggest that Swiss-type cheese could be used to deliver probiotic strains of propionibacteria to the human intestine.