ANTIBACTERIAL ACTIVITY AND ORGANIC ACIDS FORMATION BY LACTOBACILLUS SP. ORIGINATED FROM PICKLED GUAVA AND PAPAYA

Abstract

Lactic acid bacteria (LAB) produce several antibacterial compounds, including organic acids that inhibit many types of pathogenic bacteria. The antibacterial activity of LAB with the ability to inhibit growth of pathogenic bacteria associated with foodborne illness is seen as a natural way to improve food safety. This study was carried out to isolate and identify LAB from local pickled guava (Psidium guajava) and papaya (Carica papaya) and to evaluate their antibacterial activity against selected foodborne pathogens. Standard method was used for the isolation of LAB, while identification was done based on their morphological characteristics, biochemical reaction and polymerase chain reaction (PCR) amplification of 16S rRNA gene and sequencing. This study evaluated the ability of cell free supernatant (CFS) of the identified LAB to inhibit the growth of selected Gram-positive and Gram-negative foodborne pathogens through microtiter plate method. Determination of the organic acids formation in the CFS that are responsible for the antibacterial activity of the LAB was also conducted using high-performance liquid chromatography (HPLC). The results showed that three LAB from the genus Lactobacillus have been successfully isolated and identified as Lactobacillus plantarum (LABP), Lactobacillus reuteri (LABR) and Lactobacillus paracasei (LABC). All three Lactobacillus sp. were able to demonstrate antibacterial activity against foodborne bacterial pathogens used in this study. The results also suggested that the antibacterial activity of CFS of all three Lactobacillus sp. was due to organic acids production.