Isolation and Identification of Lactic Acid Bacteria with Antibacterial Activity in Pickles and Their Bacteriocin Production Characteristics(酸菜中具有抑菌活性乳酸菌的分离鉴定及其产细菌素特性)
摘要
Bacteriocins from different lactic acid bacteria have been successively isolated currently, however, these bacteriocins often suffer from the problem of a narrow antibacterial spectrum. Exploring new bacteriocins with broad-spectrum antibacterial properties has important theoretical value and application prospects. Commercially available pickled vegetables (sauerkraut) of 8 different brands with a long shelf life were selected as materials and bacteriostasis tests were done using Penicillium as indicator bacteria, the strain L<sub>3</sub> which could produce bacteriostatic substances was screened out. The strain was identified as Lactobacillus plantarum and named Lactobacillus plantarum L3 after physiological and biochemical identification and 16S rDNA sequencing analysis, and the NCBI serial number was assigned MT781360. The bacteriocin L3 showed the strongest bacteriostatic activity when the strain L<sub>3</sub> was cultured in MRS medium at 37℃ for 18-24h. The cell-free supernatant was extracted with ethyl acetate and purified by Sephadex G-50 gel filtration on a dextran gel column, and then subjected to Trinice-SDS- PAGE electrophoresis. The results showed that the molecular weight of the bacteriocin L<sub>3</sub> was around 4-5kDa. The bacteriocin L3 was sensitive to proteases, but its activity was not affected by catalase, indicating that the bacteriocin L3 was proteinaceous substance. The bacteriocin L3 still kept high antibacterial activity after subjected to 60-100℃ treatment for 20min or 121℃ treatment for 15min and was stable over the range of pH 2-10. In addition, the bacteriocin L3 had good antibacterial activity against Gram-positive bacteria, Gram-negative bacteria and some fungi. In summary, the bacteriocin L<sub>3</sub> produced by Lactobacillus plantarum L3 not only had good stability comparable to existing bacteriocins and the ability to kill Gram-positive bacteria, but also exerted an antibacterial effect on Gram-negative bacteria and some fungi.