PURIFICATION AND SPECIFICATION OF BACTERIOCIN PRODUCED BY SOME Lactobacillus SPP. ISOLATED FROM FOOD

Abstract

A total of 20 isolates of lactic acid bacteria (LAB) were isolated anaerobically fromdifferent food sources (Domiati cheese; raw milk and mixed pickles). Three out of 20 isolates showedhigh inhibition of growth pathogenic bacteria by well diffusion assay method and therefore they werechosen for bacteriocin production and further studies. The selected isolates were identified based onmorphological, biochemical and MALDI-TOF mass spectrometry. All of the tested species gave ascore value between 2.116 to 2.165 (100%) were correctly identified by MALDI-TOF- MS to thegenus and species levels. They were identified as L. brevis, L. plantarum and L. fermentum. Thebacteriocin was purified by salt precipitation and gel chromatography methods. The molecular weightwas determined by SDS-PAGE and amino acid composition was also analysed. The purifiedbacteriocin was characterized and found to be thermostable at temperatures up to 90°C for 30min, pHfrom 3 to 11 and its activity improved in the presence of Tween 80, SDS and EDTA. The contents ofbacteriocin from the acidic amino acid residues aspartic + glutamic (asp+glu) were 0.74% for all testedsamples. The contents of the basic amino acids argnine + lysine + hisitidine (arg + lys + his) were0.23% for all the tested samples.