Occurrence of bacteria with technological and probiotic potential in Argentinian human breast-milk

Breast milk can be a source of potential probiotic bacteria, but the technological capacity of isolates obtained from this source is not always guaranteed. We aimed at isolating lactobacilli from breast milk samples collected in Argentina, focusing on isolates with functional and technological potential as probiotics. Fourteen Lactobacillus and one Bifidobacterium isolates were obtained from 164 samples donated by 104 mothers. The isolates preliminarily identified by MALDI-TOF, and then the identity was confirmed by partial 16S rRNA gene sequencing. Hydrophobicity was determined (hexadecane and xylene partition). The strains were also co-cultured with murine RAW 264.7 macrophages for screening the capacity to induce the anti-inflammatory cytokine interleukin (IL)-10. Hydrophobicity ranged from 7.4 and 95.9%. The strains Lactobacillus gasseri (70a and 70c) and Lactobacillus plantarum (73a and 73b) were the strains with a higher capacity to induce IL-10 production by macrophages. The technological application was evaluated by freezing dried in 10% lactose or 10% polydextrose. The survival was assessed after accelerated (37 °C, 4 weeks) or long-term (5 and 25 °C, 12 months) storage. Except for Lactobacillus gallinarum 94d, strains lost less than 1 Log10 order cfu/g after long-term (12 months) storage at 5 °C in lactose and polydextrose as protectants. A low correlation between survival to accelerated and long-term storage tests was observed. L. gasseri (70a and 70c) and L. plantarum (73a and 73b) deserve further studies as potential probiotics due to their capacity to induce IL-10 from murine macrophages and their hydrophobicity. In special, L. plantarum 73a was able to confer enhanced protection against Salmonella infection by promoting the immunity of the small intestine.