Abstract This study involves the isolation and identification of the lactic acid bacterium Leuconostoc mesenteroidesfrom dairy product (cheese) and variable plant material by the colony morphology and routine confirmative biochemical reactions. From sixty isolates were collected, 19 isolates were belonged to Leuconostocspecies and only 10 of them were Lc. mesenteroides subsp. mesenteroides. All isolates were bacteriocin producer, and the inhibitor activity is tested against Listeria monocytogenes.The purification of the bacteriocin from the selected isolates was carried out by two steps including cation exchange chromatography by using CM-Sepharose CL-6B and gel filtration by using Sepharose 6B followed with HPLC. The purified bacteriocin was named bacteriocin NEF42 according to the isolate NEF42. For Characterization of purified bacteriocin the molecular weight was determined by gel filtration on Sepharose 6B column, and it was about (1724.6) Daltons.