STUDYING THE ANTAGONISTIC EFFECT OF ISOLATED LACTOBACILLUS FROM SOIL WHERE NATIVE YOGURT IS PROCESSED AGAINST PATHOGENIC BACTERIA

Lactic acid bacteria interfere to improve the taste of food products and and to prevent the growth of food spoilage organisms and pathogens with producing antimicrobial substances called bacteriocin. To study the antagonistic effect of isolated Lactobacillus from soil where native yogurt is processed against pathogenic bacteria is the purpose of this study.
In this cross-sectional study, Lactobacillus isolated from the soil contaminated with native yogurt waste were identified with the help of biochemical methods. The antimicrobial quality of supernatant fluid was tested against five pathogenic bacteria using diffusion agar and disk diffusion agar methods. Each test was repeated three times to reduce error and inhibition zone diameter measured then their antimicrobial ability were compared.
According to the results, three species of Lactobacillus were identified. These bacteria included Lactobacillus casei, plantarum and delbrueckii. Also, these bacteria showed their good antimicrobial ability against pathogenic bacteria. The most antibacterial effect was abserved from Lactobacillus casei against Staphylococcus aureus in well diffusion agar method with inhibition zone diameter of 18.66 mm.
A great variety of bacteria producing bacteriocin with antibacterial activity against pathogenic bacteria exist in traditional dairy products, and it is recommended to use them in the production of industrial dairy products.