Identification of Lactic Acid Bacteria Isolated from Nigerian Foods: Medical Importance and Comparison of Their Bacteriocins Activities

Abstract

Lactic acid bacteria (LAB) are a group of Gram-positive, non-spore forming, cocci or rods, which produce lactic acid as the major end product during the fermentation of carbohydrates. The genera Lactobacillus, Lactococcus, Leuconostoc, Pediococcus, and Streptococcus are important members of this group. The taxonomy of lactic acid bacteria has been based on the Gram reaction and the production of lactic acid from various fermentable carbohydrates.The classification of lactic acid bacteria into different genera is largely based on morphology, mode of glucose fermentation, growth at different temperatures, and configuration of the lactic acid produced, ability to grow at high salt concentrations, and acid or alkaline tolerance. Based on sugar fermentation patterns, LAB are classified into homofermenters and heterofermenters. Lactic acid bacteria have been used in the treatment of infections and in the production of foods, especially fermented foods (such as yoghurt, Cheese, etc.) because they can produce several compounds that contribute to taste, smell, color, and texture of the foods. In addition, they can produce antimicrobial substances including bacteriocins. LAB have the ability to inhibit pathogenic and food spoilage bacteria. The bacteriocins synthesized by different lactic acid bacteria inhibited the growth of the test organisms used and this was observed through the production of  zones of inhibition on the plates.

Keywords: Generally regarded as save (GRAS), bacteriocin, MRS agar, nisin, lactic acid bacteria (LAB), heterofermenter, homofermenters, Bifidobacterium, acidophiline, bulgarican