Isolation & Characterization Of Leuconostoc Mesenteroides From Cheese – Part 3

RESULTS AND DISCUSSION:
Isolation of Leuconostoc:

From the cheddar cheese, two types of colonies were isolated. One colony was yellow colored shiny, smooth and entire marginated. And the other was pale white, slimy, smooth colonies. Gram staining results showed: 1) gram positive bacilli, 2) gram positive cocci, and 3) gram positive coccobacilli. So to isolate Leuconostoc from other LAB organisms, vancomycin was added to the MRS medium.

Characterization of Leuconostoc:
Cultural & Biochemical characteristics - Results
Gram’s staining Gram positive, coccobacilli
Motility Motile
Capsule staining Non-capsulated
Spore staining Non-sporing
Growth at 37oC +
Growth at 30oC +
Growth at 4oC +

On MRS medium:
At 37oC Pale yellow colored, smooth, slimy,
entire marginated, convex colonies.

At 4oC In refrigeration, colonies turned white,
and slow growth was observed.

On MacConkey agar medium Lactose fermenting, pink colored
colonies.

On blood agar medium Non-hemolytic, colorless colonies.

Biochemical tests:
Indole -
Methyl red -
Voges Proskauer +
Citrate -
Urease -
Arginine -

Carbohydrate fermentation tests:
Glucose + (acid and gas)
Arabinose +
Lactose +
Mannitol -
Sucrose +
Dextrose +
Maltose +

Discussion:

From the three different colonies isolated from cheese (fig-1), Leuconostoc was isolated separately by its specific vancomycin resistant character (fig-2). Species was identified by its biochemical and carbohydrate tests. First, Leuconostoc mesenteroides was differentiated on the basis of Arginine hydrolysis. Only L.cremoris and L.mesenteroides is Arginine hydrolyser and both are possible in cheese. Secondly, Arabinose fermenters. Between both the species, only L.mesenteroides is Arabinose fermenters (Bettache Guessas and Mebrouk Kihal, 2004). Thus the species was confirmed as Leuconostoc mesenteroides.