Screening, isolation and characterization of probiotically safe lactic acid bacteria from human faecesfor biofilm formation

Abstract

Lactic acid bacteria (LAB), one of the most important human friendly bacteria found in the digestive tract (gut), due to their secretions that inhibit the pathogenic microbes. The present study was aimed at screening of such LAB from faecal samples for various characteristics, particularly in relation to the biofilm formation. Total 110 LAB isolates were obtained from infant and adults faecal samples. All isolates showed catalase negative and inability to lyse the human red blood cells (RBCs) hence considered as safe for humans. Among all 110 isolates, 38 isolates (44.44%) showed protease secretion and all isolates showed biofilm formation abilities. Protease secretion indicated major role in protein digestion in gut, however biofilm formation showed sticking ability to gut and inhibition of pathogenic microbes. Almost more than 80% of isolates were able to tolerate conditions that mimic the gastro intestinal tract i.e. bile salt concentration and acidic environment, which qualifies them to be used as potential probiotic organism. Isolate RP-29was the only isolate showed 82% bile tolerance at 1% concentration, 58% tolerance in acidic pH 2 and 95% biofilm formation. Biofilm formation means secretion of exopolysaccharide(EPS) and was enhanced by supplementation of glucose, MgSO4, MnSO4 and tween 80 in MRS medium. Using 16S rRNA sequencing, the isolate RP-29 was identified as Pediococcusacidilactici. Based on thebile-acid tolerance and biofilm formation activities, P. acidilacticifound as a potent probiotic strain and could prove to be beneficial in controlling chronic diseases caused by pathogenic microbes.