Isolation And Purification Of Antimicrobial Substance Produced By Leuconostoc mesenteroids For Using As Inhibiter For Some Pathogenic Bacteria


Abstract : Leuconostoc mesenteroids was isolated from molasses obtained from Mosul sugar factory as a byproduct, using the morphological. The Leuconostoc mesenteroids antimicrobial substances were extracted and purified by centerfuge force with the aid of chloroform, methanol, and acetone. The results showed that the rate of the growth of bacteria increased with the increase in the incubation period, the total number of bacteria reached 115 * 10 cfu/ml after 24 hours of incubation and then the number decreased after 48 hours to 47 * 10 cfu/ml.. In case of the production of inhibition substances, it appeared that the inhibiting substances continued to increase with incubation, the diameter of the inhibition zone for Staph. aureus was 10 mm. after 24 hours and increased to 12 mm. after 48 hours. Results also showed, that the heat treatments at 60, 80, and 100 c for 30 seconds were not affective on the inhibition , the inhibition zones stayed more or less stable, the zones for the used temperatures were 11, 9, and 7 mm. respectively. With regard to the effect of pH, it appeared that the most effective pH value was pH 5which resulted in an inhibition of 12 mm. The test bacteria showed different response to the inhibiting substances, Staph aureus was the most sensitive, were as E. coli was the most resistant to inhibition, the dimeter of the zones for both were 12 and 5 respectively. The inhibition for the other test bacteria; B. subtilus , Proteus bulgares and Salmonella typhi were 10, 6, 6 mm. respectively. In conclusion, the use of Leuconostoc merenteroids in fermented dairy product could be beneficial in elongating the shelf life of the products due to the production of the inhibiting substances which are affective to many pathogenic bacteria especially in fermented milk ,sour cream cottage cheese and ice cream.