Characterization and antimicrobial activity of bacteriocin 217 produced by natural isolate Lactobacillus paracasei subsp paracasei BGBUK2-16

The strain Lactobacillus paracasei subsp. paracasei BGBUK2-16, which was isolated from traditionally homemade white-pickled cheese, produces bacteriocin 217 (Bac217; similar to7 kDa). The onset of Bac217 biosynthesis was observed in the logarithmic phase of growth, and the production plateau was reached after 9 or 12 h of incubation at 37 and 30degreesC, respectively, when culture entered the early stationary phase. Biochemical characterization showed that Bac217 retained antimicrobial activity within the range of pH 3 to 12 or after treatment at 100degreesC for 15 min. Bac217 antimicrobial activity also remained unchanged after storage at 4degreesC for 6 months or -20degreesC for up to 12 months. However, Bac217 activity was completely lost after treatment with different proteolytic enzymes. BGBUK2-16 contains only one plasmid about 80 kb in size. Plasmid curing indicated that genes coding for Bac217 synthesis and immunity seem to be located on this plasmid. Bac217 exhibited antimicrobial activity against some pathogenic bacteria, such as Staphylococcus aureus and Bacillus cereus. Interestingly, Bac217 showed activity against Salmonella sp. and Pseudomonas aeruginosa ATCC27853. The inhibitory effect of BGBUK2-16 on the growth of S. aureus in mixed culture was observed. S. aureus treatment with Bac217 led to a considerable decrease (CFU/ml) within a short period of time. The mode of Bac217 action on S. aureus was identified as bactericidal. It should be noted that the strain BGBUK2-16 was shown to be resistant to bacteriocin nisin, which is otherwise widely used as a food additive for fermented dairy products