Lactic Acid Bacteria Profile of Some Selected Food Products and Their Ability to Produce Bacteriocins

Abstract

Lactic acid bacteria (LAB) commonly used as starter cultures in foods is known to produce antimicrobial substances such as bacteriocins, hydrogen peroxide and organic acids. They have great potential as food biopreservatives. The present study was aimed at profiling lactic acid bacteria of some selected food products and bacteriocin production from various food products. Different food samples comprising four each of cucumber, fresh fish, fresh milk (nunu), meat, ogi, cheese, yoghurt, and tapioca making it a total of thirty two (32) was bought in area markets in Calabar Metropolis. Serial dilutions of these samples were prepared and inoculated by pour plate method on MRS medium and incubated. It was observed that the lactic acid bacteria loads ranged from 1.11±0.41 × 102 cfu/ml(g) for fresh milk to 4.62 × 103 cfu/ml(g) for cheese. As for the distinct colonies, cheese had the highest 22 while silage had the lowest 9. Others were 21 for fresh milk, 20 for fufu, 19 for ogi, 18 for yoghurt, 15 for meat, 14 for cucumber and 12 for fish. The isolates were identified based on morphological, physiological and biochemical analysis using API 50 CHL kit. One hundred and fifty five morphologically distinct colonies of lactic acid bacteria isolated from these food samples were screened for bacteriocin production. Only 26 of these were found to be bacteriocin-positive indicating their ability to produce bacteriocin. The isolates identified included Lactobacillus sp, Leuconostoc sp, Lactococcus spp, Enterococcus sp and Pediococcus sp. This research extends our knowledge of the ubiquitous distribution of lactic acid bacteria in foods. These bacteriocin positive isolates can, therefore, be used in food preservation and control of food borne pathogens.