Bifidobacteria (246 strains in total) were isolated from rectal samples of infants and adult humans and animals, and from intestinal samples of calves. Twenty-five strains grew well on mucin: 20 from infants, two from adults, and three from goatlings. Poor or no growth on mucin was observed in 156 bifidobacterial strains of animal origin. The difference between human and animal isolates in ability to grow on mucin was significant at p < 0.001. Nine human strains with the best growth on mucin were identified as Bifidobacterium bifidum. These strains produced extracellular, membrane-bound, and intracellular mucinases with activities of 0.11, 0.53, and 0.09 μmol/min of reducing sugars per milligram of protein, respectively. Membrane-bound mucinases were active between pH 5 and 10. The optimum pH of extracellular mucinases was 6-7. Fermentation patterns in cultures grown on mucin and glucose differed. On mucin, the acetate-to-lactate ratio was higher than in cultures grown on glucose (p = 0.012). We showed that the bifidobacteria belong to the mucin-fermenting bacteria in humans, but their significance in mucin degradation in animals seems to be limited.

Institute of Animal Physiology and Genetics Academy of Sciences of the Czech Republic 142 20 Prague 4 Krč Czech Republic

Institute of Animal Science 104 00 Prague 10 Uhříněves

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