Purification and specification of bacteriocin produced by some Lactobacillus spp. isolated from food

الملخص EN

A total of 20 isolates of lactic acid bacteria (LAB) were isolated anaerobically from
different food sources (Domiati cheese; raw milk and mixed pickles).

Three out of 20 isolates showed
high inhibition of growth pathogenic bacteria by well diffusion assay method and therefore they were
chosen for bacteriocin production and further studies.

The selected isolates were identified based on
morphological, biochemical and MALDI-TOF mass spectrometry.

All of the tested species gave a
score value between 2.116 to 2.165 (100% ) were correctly identified by MALDI-TOF- MS to the
genus and species levels.

They were identified as L.

brevis, L.

plantarum and L.

fermentum.

The
bacteriocin was purified by salt precipitation and gel chromatography methods.

The molecular weight
was determined by SDS-PAGE and amino acid composition was also analysed.

The purified
bacteriocin was characterized and found to be thermostable at temperatures up to 90°C for 30min, pH
from 3 to 11 and its activity improved in the presence of Tween 80, SDS and EDTA.

The contents of
bacteriocin from the acidic amino acid residues aspartic + glutamic (asp+glu) were 0.74% for all tested
samples.

The contents of the basic amino acids argnine + lysine + hisitidine (arg + lys + his) were
0.23% for all the tested samples.