Screening Of The Strain Producing Bacteriocin And Studies On The Characteristics Of The Bacteriocin

One strain of Lactobacillus with broad antimicrobial spectrum was isolated fromintestine of animals samples and the antimicrobial substance produced by the bacterium wasstudied. Hoping to proveded the useful reference data for food biological preservative、feedadditives and medicament.1One strain of Lactobacillus with broad antimicrobial spectrum was isolated fromintestine of animals samples was identified as Lactobacillus acidophilus P3by the experimentof physiological and biochemical. The antimicrobial substance was protein and had a broadantimicrobial spectrum against some gram-negative and gram-positive bacteria. Theantimicrobial activity was still only between pH3.0and4.0and stable at121℃for20minand sensitive to protease.2Lactobacillus acidophilus P3as original strain was complexly mutated by ultravioletmutagenesis and nitrosoguanidine.Seleted70%~80%death rate, the result showed that a highbacteriocin producing mutant P302was obtained and the antimicrobial substance was154%more than the original strain,with stable heredity.3The production of bacteriocin was greatly influenced by the composition of mediumand fermentation condition. The optimum fermentation conditions for P302to producebacteriocin included the following：The formula of the modified MRS：beef extract4%、peptone0.2%、yeast extract0.8%、calcium carbonate0.4%、sucrose1%、vitamin complexed0.4%and Tween-800.3%.The initial pH7.0,the best temperature37℃、the inoculation amountis3％(v/v)、the seed age14h、the fermentation time22h.35%of the production of thebacteriocin were improved under the above conditions.4Isolation and purification of bacterioncin through3methods were studied. The resultsshowed that the bacteriocin extracted and purified from the fermentation through the pHmediated cell adsorption-desorption method was the highest. One protein could be detectedthrough Tricine-SDS-PAGE, with MW about6100Da.5Combination between the bacteriocin and O139were monitored by using thefluorescence labelling.The results showed that combined with in an hour and after18hours the fluorescence disappeard. That indicated this bacteriocin had disinfectant effect the bacteriaconcentration being4~6order less than the original between3hours and10hours.