Characterization and optimization of bacteriocin from Lactobacillus plantarum isolated from fermented beef-converted

 Many carboxylic acid bacteria (LAB) were isolated from ‘Shermout’, a well-liked Sudanese fermented beef product intended for long storage. An isolate that demonstrated significant antibacterial activity was identifiedLactobacillusplantarum PM4 supported phenotypic, physiological and biochemical characteristics and carbohydrate utilization patterns. The inhibitory activity of the partially purified bacteriocin was completely arrested by the proteolytic enzymes proteinase-k and pepsin but not by α-amylase, asserting its proteinaceous nature. The activity wasn't thanks to H2O2 as similar inhibition was obtained by cell-free supernatant (CFS) produced under anaerobic conditions. The bacteriocin showed a relative molecular mass within the range of 3-5 kDa and had a bactericidal mode of action. No significant reduction in activity was observed on heating at 60°C for 60 min, but activity was lost on heating at 100°C or autoclaving. Highest inhibitory activity was at pH 5.5 and there was appreciable reduction in activity at pH 3, 7 or 9. There was no drop-in activity at -80 or -20°C up to four weeks of storage. However, at 4 and 35°C a gradual decline in activity was observed. L. plantarum PM4 exhibited bactericidal activity against Staphylococcus aureus, Bacillus subtilis , Enterococcus faecalis, Escherichia coli ATCC25922, Klebsiella pneumoniae and Proteus vulgaris.