The results and interpretation of growth, characterization, and biochemical activity of L. mesenteroides.
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
|S.No||Cultural & Biochemical characteristics||Results|
|1||Gram’s staining||Gram positive, coccobacilli, with rounded ends.|
|5||Growth at 37oC||+|
|6||Growth at 30oC||+|
|7||Growth at 4oC||+|
|On MRS medium:|
|8||At 37oC||Pale yellow colored, smooth, slimy, entire marginated, convex colonies.|
|9||At 4oC||In refrigeration, colonies turned white, and slow growth was observed.|
|10||On MacConkey agar medium||Lactose fermenting, pink colored colonies.|
|11||On blood agar medium||Non-hemolytic, colorless colonies.|
|Carbohydrate fermentation tests:|
|18||Glucose||+ (acid and gas)|
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.
Fig-1. Isolation of Leuconostoc species from cheese (different colonies)
Fig-2. Isolation of Leuconostoc in MRS medium added with vancomycin