Molecular Characterization of Bacteriocinogenic, Antifungal and Probiotic Lactic Acid Bacteria Isolated from Chicken Gastrointestinal Tract

Abstract

In this study, bacteriocinogenic Lactobacillus plantarum isolates capable of inhibiting food- and feed-borne filamentous fungi from the gastrointestinal tract (GIT) of broiler chicken were identified using 16S rRNA gene sequencing and further evaluated for probiotic properties in vitro . Six potent lactobacilli were selected from one hundred and thirteen isolates for the present study based on their ability to inhibit both pathogenic bacteria and filamentous fungi. They were characterized using various physiological, biochemical and molecular methods. They were acetoin producers, homo fermentative, catalase-negative and producing racemic lactic acid (10 - 20 mM). All the six isolates exhibited varied sugar utilization and RAPD pattern, indicated their strain level genotypic variation. The 16S rRNA gene sequence and multiplex PCR analysis confirmed that these isolates were Lactobacillus plantarum. The isolates being resistant to low pH (2.0) and bile salt (0.6%) could survive in the gastrointestinal tract of host indicating their potential probiotic application. The isolates were non-pathogenic ( γ -hemolytic) and exhibited resistance to antibiotics ciprofloxacin, nalidixic acid, norfloxacin, nitrofurantoin, colistin and streptomycin. They demonstrated strong autoaggregating phenotype ranging from 78% to 86% and showed 49% - 61% and 30% - 46% coaggregation with E. coli MTCC 728 and L. monocytogenes MTCC 657, respectively. The percentage of hydrophobicity ranged from 16% - 33% for all the isolates showing that surface was rather hydrophilic. They exhibited β -galactosidase activity ranging from 1036 - 1179 MU, bile salt hydrolase activity assisting to reduce serum cholesterol and produced the anti- Listerial bacteriocin. The strong inhibitory activity of these isolates against food spoilage molds and bacteria with probiotic properties indicates their potential application as food preservatives.