Paper Information

Journal:   APPLIED FOOD BIOTECHNOLOGY   2016 , Volume 3 , Number 3; Page(s) 170 To 176.
 
Paper: 

ELIMINATION OF PATHOGEN ESCHERICHIA COLI O157:H7 IN GROUND BEEF BY A NEWLY ISOLATED STRAIN OF LACTOBACILLUS ACIDOPHILUS DURING STORAGE AT 5OC

 
 
Author(s):  GOODARZI ALIREZA*, HOVHANNISYAN HRACHYA, BARSEGHYAN ANDRANIK
 
* SCIENTIFIC AND PRODUCTION CENTER ARMBIOTECHNOLOGY NATIONAL ACADEMY OF SCIENCE, YEREVAN, ARMENIA
 
Abstract: 

Background and Objective: Constant use of limited number of lactic acid bacteria species in biopreservation can cause genetic degradation and or rising resistance against food pathogens or antimicrobial substances they produce. For this objective, a newly isolated strain ofLactobacillus acidophilus possessing high antimicrobial activity was evaluated as a candidate for use in biopreservation.
Materials and Methods: Antibacterial activity was evaluated by agar disk diffusion method. Hydrogen peroxide amount was measured by Merckoquant Peroxide test strips. Microbiological analysis of the ground beef infected by Escherichia coliO157: H7 and treated by Lactobacillus acidophilus GH 201was done by plating of serial dilution in physiological saline on Tryptose agar.
Results and Conclusion: The cells (109 CFU ml-1) of Lactobacillus acidophilus produced significant amount of antibacterial substances mainly hydrogen peroxide(28 and 30
mg ml-1) in sodium phosphate buffer (0.2 M, pH 6.5) and LAPTg at 5oC during submerged cultivation with no growth, respectively.
Submerged co-cultivation of Escherichia coli O157: H7 with lactobacilli in LAPTg broth at 5°C reduced the total number of the pathogen more than 2 log for 5 days. In case of solid state cultivation on agar-based medium, the maximum inhibitory zones on Escherichia coli O157: H7 lawn around the disks soaked by different amounts of washed Lactobacillus acidophilus cells appear for one-day cold exposition. The size of inhibition zone depends on the concentration of lactic acid bacteria cells. The cell suspension intended for treatment must contain 108-9 CFU ml-1 of lactic acid bacteria. Lactobacillus acidophilus reduced the initial amount (2×105 CFU ml-1) of Escherichia coli O157: H7 in ground beef up to 2 log for 5 days of solid-state co-cultivation. The application of Lactobacillus acidophilus bacteria expanded the shelf-life of ground beef due to inhibition of psychrophilic spoilage microorganisms.

 
Keyword(s): BIOPRESERVATION, E. COLI O157:H7, HYDROGEN PEROXIDE, LACTOBACILLUS ACIDOPHILUS, REFRIGERATED TEMPERATURES
 
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