Extraction of bacteriocin from <I>L. plantarum </I>and <I>L. acidophilus </I>and determination of some of its physico-chemical characteristics

Abstract

Bacteriocins are antimicrobial compounds that are produced by many different bacterial species including lactic acid bacteria (LAB). Some bacteriocins produced by LAB inhibit not only closely related species, but are also effective against food borne pathogens such as Listeria monocytogenes and many Gram – positive food spoilage causing microorganisms. The aim of the study is to isolate Lactic acid bacteria from Cucumis sativum, extract bacteriocin from the isolated LAB and determine some of its physico – chemical characteristics. The LAB was identified using conventional biochemical tests, API50CHL and molecular techniques as Lactobacillus plantarum and Lactobacillus acidophilus_. Bacteriocin extracted from the isolated LAB was tested for antibacterial activity against S. aureus and E. coli. Highest activity by zone of inhibition of 9.3+0.33mm on S. aureus was obtained. Physical, chemical and biochemical properties of the bacteriocin extract showed that, they are thermo stable (40^oC – 121^oC) active over a wide range of pH (3 – 11), inactivated by the enzyme trypsin. Addition of sodium Dodecyl sulphate (SDS), Tween 80 and Urea, reduced the antibacterial activity while addition of EDTA enhances of the antibacterial activity of the bacteriocin. The study has revealed the presence of Lactobacillus in cucumber (Cucumis sativum) which was confirmed using API50CHL and molecular techniques.

Keywords: Lactic Acid Bacteria, Bacteriocin, Antibacterial Activity, EDTA, Test Organisms