Towards the isolation of more robust next generation probiotics: the first aerotolerant Bifidobacterium bifidum strain?

This work reports on the first described aerotolerant Bifidobacterium bifidum strain. One of the main challenges for exploiting the therapeutic potential of next generation probiotics is their inclusion into functional foods, which is hampered by extreme oxygen sensitivity. This is indeed an unmet technological problem of human gut bifidobacteria. Aerobic conditions are present during the processes of producing, handling, manufacturing and storing probiotics. B. bifidum species includes several probiotic strains of invaluable therapeutic potential, but they also exhibit one of the lowest resistance to oxygen among human bifidobacteria. In this work, we present strain Bifidobacterium bifidum IPLA60003, which has the ability to form colonies on the surface of agar plates under aerobic conditions, a weird phenotype that to our knowledge has never been observed in B. bifidum. The strain IPLA60003 was generated after random UV mutagenesis from an intestinal isolate. It incorporates 26 single nucleotide polymorphisms that activate the expression of native oxidative defense mechanisms such as the alkyl hydroxyperoxide reductase, the glycolytic pathway and several genes coding for enzymes involved in redox reactions. In the present work, we discuss the molecular mechanisms underlying the aerotolerance phenotype of B. bifidum IPLA60003, which will open new strategies for the selection and inclusion of probiotic gut strains and next generation probiotics into functional foods. Further, we addressed the technological application of IPLA60003 evaluating its survival and metabolic activity in milk for 28 days. Besides, we studied the survival of the strains in fresh cultures, after freezing at -80ºC and after lyophilization by plate counts incubated in anaerobiosis and in the presence of O2. Globally, technological performance of strain IPLA60003 was better than other two non-aerotolerant B. bifidum strains.