Characterization of new strain Lactobacillus paracasei I-N-10 with proteolytic activity: Potential role in decrease in β-casein immuno-reactivity

The proteolytic activity of thirty-three LAB isolates from Mongolian tarag was tested on skimmed milk. The strain displaying the highest proteolytic activity was purified and presented by 16S rDNA sequencing 99.9 % homology with Lactobacillus paracasei 1-4-2A. It was named L. paracasei I-N-10. Proteases of L. paracasei I-N-10 hydrolyze predominately β-casein and in some level αS2-casein; hydrolysis of αS1-casein was not observed. Proteolytic activity was optimal at 42 °C and neutral pH. Proteases of L. paracasei I-N-10 were inhibited by serine- and metalloproteases inhibitors. PCR amplification revealed the presence of prtP gene, which was identical to prtP gene of L. paracasei genus. Mass spectrometry analysis of β-casein hydrolysate allowed to characterize 7 peptides resulting from proteolysis by L. paracasei I-N-10. The isolated strain was able to cleave β-casein in different sites including 2 of the major linear epitopes implicated in its allergenicity. Being sensitive to main antibiotics classes, L. paracasei I-N-10 could be considered as safe and used as starter culture with a potential role in decreasing β-casein immuno-reactivity.