Improvement of Bacteriocin Production by Natural Zeolite and Detection of Antibacterial Activity of Leuconostoc carnosum Purified Carnosin

The purpose of this study was the improvement of bacteriocin production due to importance of bacteriocin in biotechnology.  Zeolite was used for the first time in this study to support and improvement of bacteriocin production through the ability to increase the bacterial biomass. Zeolite is a mineral that consists mainly of aluminosilicate. One –hundred eighty isolates belonging to the lactic acid bacteria were obtained from 120 samples of different parts of cauliflower and broccoli .The vegetable samples were taken from different markets in Baghdad city for 3 months. Lactic acid bacteria (LAB) isolates were identified by standard diagnostic methods. Bacteriocin production was detected by measuring the inhibition zone towards indicator pathogenic bacterial isolates. The isolates were screened to determine the most efficient producer which caused the largest inhibition zone and it chosen. The most efficient producer was Leuconostoc carnosum after confirmed identification using the VITEK®2 System. The results showed the maximum bacteriocin production with a specific activity of 1093 AU.mg-1 protein when added 1.5%. The active peptide was purified from the cell-free supernatant of Leuconostoc carnosum in three processes: (1) Ammonium sulfate for precipitation with 40-60% saturation (2) ion-exchange chromatography (3) gel filtration chromatography. The purified carnosin was characterized by determining the molecular weight using SDS PAGE (8KDa) in size .Carnosin had lost antimicrobial activity with different protease treatments (pepsin, trypsin and proteinase K). Carnosin was maintained its activity at 100oC but lost 13% of it at 121oC after 15 min.; Carnosin resistance for changed in PH range of 2.0-11.0, while lost 15% of its activity at pH 12.0. Also the organic solvent, surfactant and metal ion salt do not effect on its activity. The purified carnosin appeared a board range of antimicrobial activity against many pathogenic and food-borne spoilage bacteria such as Escherichia coli, Pseudomonas aeruginosa, salmonella typhi, Listeria monocytogenes and Staphylococcus aureus.