Antibacterial potential of lactic acid bacteria isolated from local pickled Eleiodoxa conferta (kelubi) against selected foodborne pathogens

Aims: Pickled fruits are a popular condiment not only in Malaysia but throughout the world. Lactic acid bacteria (LAB) are known to be able to produce several antibacterial compounds during the pickling process. Pickled Eleiodoxa conferta or kelubi is among the commonly consumed pickled fruits in Malaysia and may be a promising source of LAB. This study was carried out to isolate and identify LAB from local pickled E. conferta and to determine their antibacterial activity against foodborne pathogens. Methodology and results: The isolation of LAB was conducted using standard methods and the isolated colonies were preliminarily identified based on their morphology on De Man, Rogosa and Sharpe (MRS) agar, Gram-positive staining characteristics and their catalase-negative reactions and subsequently chosen for identification with polymerase chain reaction (PCR) amplification of the 16S rRNA gene and sequencing. A total of four LAB isolates were successfully isolated and identified: Lactobacillus brevis (LABK1 and LABK2), L. plantarum (LABK3) and Leuconostoc mesenteroides (LABK4). The antibacterial activity of the identified LAB was determined against 10 commonly known foodborne bacterial pathogens using LAB cell cultures by agar spot test method. The antibacterial activity was also evaluated using the cell free supernatant (CFS) of the LAB through agar well diffusion method. All four LAB cultures were able to demonstrate antibacterial activity and inhibited five Gram-positive and five Gram-negative bacterial pathogens. Conclusion, significance and impact of study: This study demonstrated that the isolated LAB from E. conferta has antibacterial effects against several foodborne pathogens. These LAB strains may have potential as a natural food preservative.