Dairy products as sources of methanogens for humans

ABSTRACT Methanogens are detected in human gut from the first moments of life and there is a diversification of methanogens during infancy. However, the sources of acquisition of methanogens are not well elucidated. We therefore investigated 56 dairy products as potential sources of methanogens by applying molecular biology. In the presence of negative controls, we obtained an overall prevalence of methanogens in 85.7% (48/56) of samples by real-time PCR. Further PCR-sequencing identified 73.2% (41/56) of Methanobrevibacter smithii . We also found for the first time in dairy products 1.8% (1/56) of Methanobrevibacter oralis , 7.1% (4/56) of Methanobrevibacter millerae , 1.8% (1/56) of Methanobrevibacter ruminantium , 1.8% (1/56) of Methanocorpusculum sp. We observed a significant presence (p-value=0.001) of methanogens in fermented dairy products compared to unfermented dairy products. This study gives credit to the fact that dairy products could be considered as a source of methanogens for humans, especially for children.