Eleven yoghurt samples were collected from local markets in Baghdad to isolate Lactobacillus buchneri. Only 3 isolates of L. buchneri were found and the isolate No. 3 was the most producer of bacteriocin. Bacteriocin was adsorbed 100% onto silicic acid at pH 6.0-7.0. Below or above these pH values, adsorption was decreased, ranging between 35 and 90%. Therefore, pH 6.0 was used for the purification procedure. The purification procedure including silicic acid adsorption/desorption and cation-exchange chromatography (CEC) resulted in a 11.11 fold increase in the final specific activity of pure bacteriocin (1176.47 Au/mg) compared to the culture supernatant which was 32.64 Au/mg. The molecular weight was determined to be about 3.4 kDa. The bacteriocin lost its activity completely after treatment with proteolytic enzymes and it was resistant to non-proteolytic enzymes. The results indicated that bacteriocin at both concentrations (500 and 1000 μg/ml) possesses significant antimicrobial activity against Vibrio parahaemolyticus in contrast with control (P<0.01) and the antimicrobial activity of crude and purified bacteriocin at the concentration of 1,000 μg/ml were higher than the other concentration (500 μg/ml). The antimicrobial activity of purified bacteriocin was significantly higher than that of crude bacteriocin (P<0.01).