Molecular Characterisation and Antagonistic Activity of Fructophilic Lactic Acid Bacteria Isolated from Selected Fruits

Abstract

Fructophilic lactic acid bacteria have very unique biochemical characteristics when compared to other LAB in relation to their hexose sugar metabolism and utilization of oxygen. The aim of this study was to isolate and identify lactic acid bacteria from fresh fruits and determine their antibacterial activity against pathogenic and spoilage organisms.84 fresh fruit samples comprising of Mango, Apple, Oranges, Watermelon, Guava, Lime were purchased from major fruit markets. Lactic acid bacteria were isolated from fruits using modified Man Rogosa Sharpe media and phenotypically identified using Gram staining, biochemical tests and API 50CH Kit. Polymerase Chain Reaction (PCR) analysis and 16SrRNA sequences were used to confirm their identity. Antibacterial activity of the cell free supernatant of the LAB was carried out against four pathogenic and two spoilage bacteria respectively. The result obtained indicate that one hundred and ninety fructophilic lactic acid bacteria were isolated and identified into four groups: Pediococci, Lactobacilli, Enterococci and Leuconostoc respectively. Lactobacillus plantarum had the highest frequency of occurrence while Lactobacillus alimentarium had the least. Out of 190 FLAB isolates obtained, only 98 showed inhibitory activity against the pathogenic and spoilage organisms tested, only 23 of the tested isolates were able to produce bacteriocin as shown by the effect of enzyme treatments. This study clearly suggests that Fructophilic LAB share similar traditional attributes with those obtained from fermented and dairy food, hence the need to utilize them in food processing and preservation.