Occurrence of Lactobacilli with Probiotic Potential in Argentinian Breast Milk

Differences in environmental and gut microbiota are factors that favor the exploration of locally sourced probiotics. Such probiotics target the particular populations to improve their gut health. This could lead to local developments and activities which may pave the way to their application in social programs. Such probiotics are particularly beneficial for people in developing countries, who generally lack access to affordable commercial probiotics and are more often exposed enteric infections.

104 mothers donated 161 breast milk samples. Lactobacilli were isolated using MRS agar, preliminary identified by MALDI-TOF and then the identity was confirmed by partial 16S RNA sequencing. Hydrophobicity was determined (hexadecane and xylene partition). Strains were freeze-dried in 10% lactose or 10% polidextrose and survival was assessed after accelerated (37°C, 4 weeks) or regular (5° and 25°C, 12 months) storage. Strains were co-cultured with murine RAW 264.7 macrophages for screening the capacity to induce the anti-inflammatory cytokine IL-10.

14 LAB isolates were obtained and identified as L. plantarum (7 isolates), L. gasseri (3), L. fermentum (2), L. rhamnosus (1) and L. gallinarum (1). Hydrophobicity ranged from 7.4 and 95.9%. L. gasseri 70a, 70b and 73a were the strains with higher hydrophobicity and capacity to induce IL-10 production by macrophages. Very low correlation between survival at 37°C/1 month and 5°/12 months was observed. Better correlation at 25°C was observed for lactose (R² = 0.77) compared to polydextrose (R² = 0.65). Less than 1 log order of cell death was observed in polydextrose for L. gasseri 70a, 70b and 73a after 12 months of storage at 5°C.

Three L. gasseri strains were isolated, which displayed promising functional and technological properties for further studies on their health promoting properties, to be used as locally sourced probiotic strains.