Characterization of bacteriocin-like inhibitory substances (BLIS) from lactic acid bacteria isolated from traditional Azerbaijani cheeses

The lactic acid bacteria (LAB) of southern Caucasus region present a special interest due to the diversity of lactic flora used for fermentations by various local populations during thousands of years. Four LAB strains, not identified previously, isolated from Motal and Brunza typical Azerbaijani cheeses were subjected to phenotypic identification and three of them could be identified as Lactobacillus paracasei subsp. paracasei and one as Lactobacillus rhamnosus. Test strains such as Lactobacillus bulgaricus 340 and Saccharomyces cerevisiae were inhibited by the four isolated strains. Antibacterial activity against Escherichia coli HB 101 was detected in Lactobacillus paracasei BN ATS 8w and L. rhamnosus FAZ 16m. L. paracasei BN ATS 5w and 8w, and L. rhamnosus FAZ 16m showed inhibitory effect on Staphylococcus aureus Cip 9973. The inhibition of Candida pseudotropicalis was detected only when using L. paracasei species BN ATS 5w and 7w. Culture of Listeria innocua was insensitive to the antimicrobial substances of all the studied strains. Complete inactivation or significant reduction in antibacterial activity was observed after treatment of cell-free supernatants with pronase E and proteinase K, but not with trypsin (except for L. rhamnosus FAZ 16m), indicating the protein nature of the active agents. Amylase treatment totally inactivated the substances of L. paracasei, what implies the importance of glycosylation for the activity. The activities of all the bacteriocin-like substances from studied LABs were stable over a wide pH range from 3 to 11.