Purification And Partial Characterization Of A Bacteriocin Produced By A Lactobacillus Plantarum

In recent years, with the abuse of antibiotics, large amount of drug-resistant strains have emerged, which caused serious problems of food safety and environmental pollution. Bacteriocins, as a new biological preservatives, have attracted much attention due to the characteristics of highly efficiency, non-toxic, acid tolerance, thermal stability, no residual, no drug resistance and so on. As a kind of “Green preservatives”,bacteriocins have gained more and more attention recently.This study focused on a strong-antibacterial lactic acid strain isolated from Chongqing pickles, bacteriocin produced by it has been purified, parts of physical and chemical characterizations were analyzed, as well as its preliminary inhibitory mechanisms. The main results are as follows:(1) LAB KX041, which was isolated from Chongqing pickles, was tested having the highest antibacterial activity. After the 16 S rDNA sequencing and construction of the phylogenetic tree, it was identified as Lactobacillus plantarum.(2) Purification of the bacteriocin produced by Lactobacillus plantarum KX041: The crude bacteriocin was obtained by ammonium sulfate precipitation, then it was purified by HiTrap Q XL anion exchange column and further purification was taken by HPLC.(3) Physico-chemical characteristics of the bacteriocin produced by L. plantarum KX 041 were analyzed in this study: the bacteriocin was considered to be heat stable and storage stable that the inhibitory activity had been maintained after treated at 121℃ for 20 min and stored at- 40℃ for 1 year. As with a wide range of pH tolerance, the bacteriocin showed high inhibitory activity between pH 2 and 11, especially under acidic condition. However, it was not sensitive to protein enzymes: when treated by papain, the activity decreased, however pepsin, trypsin, and proteinase K had not affected the activity obviously. The bacteriocin has a wide antibacterial spectrum not only against some common food-borne pathogens include Gram-positive and Gram-negative bacteria, but also some drug-resistant strains.(4) Scanning electron microscopy( SEM) and transmission electron microscopy( TEM) were used to observe the susceptible strains which treated by the bacteriocin, the destruction of cell membrane inferred the site of action of the bacteriocin may be located on the bacterial cell membrane.