Caractérisation de la production de la vitamine B12 chez les bactéries probiotiques.

Abstract

In the present study, eleven beneficial isolates from faeces of exclusively breastfed infants and seven more from human milk origins were explored for their vitamin B12 productivity. For this purpose, their safety and antioxidant activity were estimated in vitro by measuring the DPPH free radical scavenging activity and the FRAP iron reducing capacity. Their antimicrobial activity against selected pathogenic strains was studied by the sink method. The results found reflected DPPH free radical scavenging activities of our probiotic isolates in the range of 16 to 32.1%. However, there is a disparity in this antioxidant capacity between isolates from human milk and those from infant faeces. By the FRAP method, the data were not changed, the antioxidant activities were lower than 1 in the lactic strains SL3, SL7 and SL9 and about 1.34% in the SL4 isolate which marks its superiority. The intestinal strains showed antioxidant activities ranging from 1.22-1.48%; excepted SS10 and SS11 whose values were lower than 1%. Supernatants obtained from the 11 faecal isolates showed varying degrees of inhibitory activities. The most interesting faecal isolate was SS8 where the calculated inhibition diameters were all greater than or equal to 10 mm, excepted those against the two pathogens S. aureus and Klebsiella pneumoniae where the inhibition zones were 8 to 9 mm. The supernatants obtained from the seven lactic isolates of breast milk origin also showed varying degrees of inhibitory activity and would appear to be more interesting compared to those calculated for the beneficial faecal isolates. All isolates were able to secret cobalamin. This productivity was found to be similar at both λ=240 and 245 nm wavelengths. It would be interesting to incorporate these strains in the composition of probiotic foods in order to enrich them in situ with B12 vitamin.