Propionibacteria isolated from rumen used as possible probiotics together with bifidobacteria

The study aimed to isolate and identify propionibacteria from bovine rumen, to study their probiotic characteristics and to evaluate the interactions between propionibacteria and bifidobacteria in sour milk product. Morpholog ical and biochemical analysis serve as identification methods. Probiotic ch aracteristics of the isolated propionibacteria strains were studied through in vitro tests measuring resistance to acidity, to ox gall bile salts and to pancreatic secretion. Antimicrobial activity is tested using typical har mful bacteria as indicator organisms. Two Propionibacteria jensenii species display potential probiotic characteristics and have been selected along w ith a commercial P. freudenreichii strain to produce batches of sour milk w ith Bifidobacteria longum. These strains were separately cultivated under o ptimum circumstances and combined in different proportions. A combination r atio of 2:3 proved to be the best tested. Selected propionibacteria strains survived well and viable counts remained above the level of 10(6) cfu/ml, while B. longum concentrations decreased evenly over the 3-week cold storag e period at +6 degreesC. During the preservation period, microbiological, c hemical and sensory tests were conducted weekly. The technological properti es of the milk product do not yet come up to commercial standards. The resu lts are promising, however, and serve as the basis for the further developm ent of a new type of probiotic sour milk product.