Isolation, characterization and identification of lactic acid bacteria with antimicrobial activities found in fresh pulp of tomatoes from Ouagadougou, Burkina Faso

Abstract

The objective of this investigation was to isolate, characterize and identify lactic acid bacteria (LAB) from local tomato fresh pulps. A batch of 30 samples of Mongal cultivar tomato purchased at two markets in Ouagadougou, Burkina Faso was used as a matrix for the collection of LAB isolates. From a preliminary biochemical characterization, 97 isolates were collected based on their antimicrobial activity. Seventeen isolates (17.52 % of the isolates collected) displayed antimicrobial activities with an inhibitory zone higher than or equal to 12 mm of diameter, against one to three out to 16 pathogenic indicator strains used including bacteria, moulds and yeasts. Based on their phenotypic characteristics, the 17 isolates were regrouped and 12 representative isolates were used for the identifiation by 16S rDNA sequencing. The results showed that the 17 LAB isolates displaying antimicrobial activity, were capable of fermenting various carbohydrates, and three of them were capable of producing bacteriocin-like substances (BLS) against Salmonella infantis SKN 557 (2 isolates) and Pseudomonas aeruginosa ATCC (1 isolate). Fourtheen isolates showed inhibitory activity against both A. flavus and A. fumugatus. The isolates identified belong to the species Lactobacillus plantarum (50% of the isolates) , Lactobacillus fermentum (25%), Lactobacillus pentosus (8.33%), Lactobacillus plantarum/pentosus (8.33%) and Pediococcus acidilactici (8.33%) with a dominance of Lactobacillus genus which represents 91% of the identified isolates against 9% of Pediococus genus. The isolates revealed interesting properties and shoud be potential candidates to be used as starter cultures for food fermentation and preservation including fruits and vegetables products. This study is a contribution to update knowledge on lactic acid bacteria from tomato and provides a selection of isolates with functional properties that can be used as starter cultures for lactofermentation of fruits and vegetables based products.