Partial purification and characterization of a broad‐spectrum bacteriocin produced by a <i>Lactobacillus plantarum</i> zrx03 isolated from infant's feces

Abstract

<i>Lactobacillus plantarum</i> zrx03 was a bacteriocin-producing strain isolated from infant's feces. The fermentation supernatant produced by this strain could strongly inhibit <i>Escherichia coli</i> JM109 ATCC 67387, <i>Staphylococcus aureus</i> ATCC 25923, and <i>Listeria monocytogenes</i> CICC 21633, in which the diameter of inhibition zone was 12.83 ± 0.62 mm, 15.08 ± 0.31 mm, 6.75 ± 0.20 mm, respectively, compared with lactic acid bacteria N1, N2, M13, M21, M31, and M37. According to amplification of 16S rRNA gene and identification of phylogenetic tree, this strain had a 1,450 bp sequence and 100% identity to the <i>L. plantarum</i> strain. Based on the influence of different protease treatments, such as pepsin, trypsin, papain, and proteinase K on the antimicrobial activity, this antimicrobial substance was considered to be a natural protein. Using bacteriocin produced by this strain as study object of this experiment, it had been extracted from ammonium sulfate precipitation and different organic solvents. The results showed that ethyl acetate was selected as the optimal solution to crude extraction of bacteriocin after comparing ammonium sulfate precipitation method and organic solvent extraction method, such as n-butanol, n-hexane, dichloromethane, trichloromethane, in which the diameter of the inhibition zones was above 28 mm. Results also showed the inhibition spectrum of the obtained bacteriocin had a broad spectrum of inhibition which could inhibit Gram-positive, Gram-negative, yeast. Especially, it could effectively inhibit <i>S. aureus</i> ATCC 25923, <i>Bacillus subtilis</i> CICC 10002, <i>Bacillus anthracis</i> CICC 20443, <i>E. coli</i> JM109 ATCC 67387, and <i>Salmonella</i> CMCC 541, and the zone diameter of inhibition has reached more than 28 mm. Moreover, it had a good thermal stability which antibacterial activity was retained 70.58% after treatment at 121°C for 30 min, and pH-stability was between pH 2.0-9.0. These results suggested bacteriocin produced by <i>L. plantarum</i> zrx03 had potential application prospects in food preservation.