Production of bacteriocin by Leuconostoc mesenteroides 406 isolated from Mongolian fermented mare’s milk, airag.

This research identifies and characterizes a bacteriocin produced by the bacteria Leuconostoc mesenteroides strain 406, extracted from fermented Mongolian mare’s milk. The bacteriocin shows potential for inhibiting harmful bacteria and suggests potential use in fermented dairy products.

Identification of Bacterial Strain

• The bacterial strain Leuconostoc mesenteroides 406 was isolated from traditional Mongolian mare’s milk called airag.
• The strain was classified based on morphological, biochemical characteristics, and carbohydrate fermentation profile.
• Additional identification was done using API 50 CH kit (a biological tool used to determine bacterial species by detection of its metabolic activity) and 16S ribosomal DNA analyses (a method for identifying and classifying bacteria based on their genetic sequence).

Characterization of Bacteriocin

• Bacteriocin produced by this strain showed potential to inhibit the growth of various harmful bacteria, including food spoilage organisms such as Listeria monocytogenes and Clostridium botulinum, which cause foodborne illnesses.
• The bacteriocin was found to be heat-resistant and insensitive to varied acid and alkaline conditions, making it stable under different environment conditions.
• Its effectiveness was compromised by several enzymatic proteins, suggesting it’s a protein-based compound.

Optimal Conditions for Bacteriocin Production

• The best conditions for bacteriocin production were found to be culturing the bacterial strain at 25°C for a duration of 24-36 hours in a nutrient-rich medium known as Man Rogosa Sharpe medium.
• Under these conditions, the bacterium could generate up to 4000 activity units of bacteriocin per milliliter of culture.

Purification and Molecular Weight of Bacteriocin

• The bacteriocin underwent a purification process, which involved ammonium sulfate precipitation, dialysis, and gel filtration chromatography to separate it from other molecular components.
• The molecular weight of the purified bacteriocin was found to be approximately 3.3 kilodaltons (kDa), a measurement obtained using a technique called sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE).

Significance and Application

• This is the first report of a bacteriocin-producing strain of Leuconostoc being isolated from traditional Mongolian fermented milk, signalling a new source of this valuable compound.
• The study suggests that such bacteriocin has potential applications in fermented milk products due to its ability to inhibit the growth of certain harmful bacteria.