Characterization of lactobacilli isolated from indigenous fermented foods and human gut with special reference to their probiotic attributes

Abstract

Lactobacilli are a group of Lactic Acid Bacteria widely used in the dairy industry nowadays. These bacteria are used as natural acidifiers for the inoculation of bulk quantities of milk, vegetables and fruits in order to produce a variety of fermented products and beverages. The market of probiotic products has expanded in the five years and most probiotic effects appear to be strain specific. Thus, there is a need for new and well characterised strains, as well as the elucidation of their mode of functional action. The objective of this study was to isolate, identify and characterise Lactobacillus strains from traditional indegenous fermented food products and children s gut as potential probiotic candidates in vitro. A model of the stomach-duodenum passage was optimised and used to screen 96 Lactobacillus isolates for their survival under simulated gastrointestinal conditions. Six strains showing good survival were selected, and identified by phenotypic and genotypic methods. All strains possessed bile salt hydrolase, as an indicator of survival to bile and of possible cholesterol utilisation, and some also hydrolysed lactose, which may serve for alleviating lactose intolerance. Furthermore, some strains could inhibit the growth of food borne pathogens by producing organic acids and H2O2, and also coaggregated with pathogens, which may enhance their removal in the gut by blocking their adhesion sites. The strains also adhered well to intestinal cells, indicating that they may at least transiently remain in the gut to exert their probiotic effects. Furthermore several strains of this group produce substances of peptide structure that possesses antimicrobial activity called bacteriocins or Antimicrobial peptides (AMPs). The only commercially available bacteriocin is Nisin produced by Lactococcus lactis. As such, the need of investigating the production of such substances from other strains of LAB to develop a technique for their production on a large scale emerged.