Degradation of food-derived opioid peptides by bifidobacteria.

Some food-derived opioid peptides have been reported to cause diseases, such as gastrointestinal inflammation, celiac disease, and mental disorders. Bifidobacterium is a major member of the dominant human gut microbiota, particularly in the gut of infants. In this study, we evaluated the potential of Bifidobacterium in the degradation of food-derived opioid peptides. All strains tested showed some level of dipeptidyl peptidase activity, which is thought to be involved in the degradation of food-derived opioid peptides. However, this activity was higher in bifidobacterial strains that are commonly found in the intestines of human infants, such as Bifidobacterium longum subsp. longum, B. longum subsp. infantis, Bifidobacterium breve and Bifidobacterium bifidum, than in those of other species, such as Bifidobacterium animalis and Bifidobacterium pseudolongum. In addition, some B. longum subsp. infantis and B. bifidum strains showed degradative activity in food-derived opioid peptides such as human and bovine milk-derived casomorphin-7 and wheat gluten-derived gliadorphin-7. A further screening of B. bifidum strains revealed some bifidobacterial strains that could degrade all three peptides. Our results revealed the potential of Bifidobacterium species in the degradation of food-derived opioid peptides, particularly for species commonly found in the intestine of infants. Selected strains of B. longum subsp. infantis and B. bifidum with high degradative capabilities can be used as probiotic microorganisms to eliminate food-derived opioid peptides and contribute to host health.

Lysozyme in breast milk is a selection factor for bifidobacterial colonisation in the infant intestine.

The objective of this work was to study the residential characteristics of bifidobacteria, which can be classified as either human-residential bifidobacteria (HRB) or non-HRB. We investigated the growth of different strains of HRB and non-HRB in human breast milk with the aim of understanding the mechanisms involved in the unique habitation of each taxon. The growth of 37 strains of different bifidobacterial species or subspecies in breast milk was investigated by incubating each under anaerobic conditions at 37 °C. The tolerance of each strain to either egg white or human lysozyme was compared. Among the infant-type HRB strains, all strains of Bifidobacterium longum subsp. infantis and Bifidobacterium breve grew well in breast milk, but the growth characteristics of B. longum subsp. longum and B. bifidum were strain-dependent. In contrast, the tested strains of adult-type HRB and non-HRB generally failed to grow and died after incubation in breast milk. Most infant-type HRB strains were tolerant to high concentrations of lysozyme, while adult-type HRB strains possessed intermediate tolerance to lysozyme, and non-HRB strains were susceptible to lysozymes of egg white or human origin. These data suggest that breast milk lysozyme content plays a central role in the exclusion of non-HRB, while other factors, together with lysozyme content, are involved in the growth inhibition of adult-type strains in human milk. Our results suggest that infant-type HRB strains would be suitable candidates for use as infant probiotics.