Leuconostoc

A genus of lactic acid bacteria

Leuconostoc is a genus of Gram-positive bacteria that are part of the family Lactobacillaceae. These bacteria are known for their role in the fermentation of foods and are commonly found in environments rich in carbohydrates, such as plant surfaces and dairy products. Leuconostoc species are important in the food industry for their ability to produce lactic acid and other metabolites that contribute to the flavor and preservation of fermented foods.

Characteristics

Leuconostoc species are cocci or coccobacilli that are typically found in pairs or chains. They are non-motile and do not form spores. These bacteria are facultative anaerobes, meaning they can grow in both the presence and absence of oxygen, although they prefer anaerobic conditions. Leuconostoc species are heterofermentative, producing lactic acid, carbon dioxide, and ethanol or acetic acid from the fermentation of carbohydrates.

Habitat

Leuconostoc bacteria are commonly found in a variety of environments, including:

• Plant surfaces
• Dairy products
• Fermented foods such as sauerkraut, kimchi, and pickles
• Wine and cider

Role in Fermentation

Leuconostoc species play a crucial role in the fermentation of foods. They are involved in the production of:

• Sauerkraut and kimchi: Leuconostoc mesenteroides is one of the primary bacteria responsible for the initial stages of fermentation, producing lactic acid and carbon dioxide, which help preserve the vegetables and develop their characteristic flavors.
• Dairy products: Leuconostoc species are used in the production of certain cheeses and buttermilk, contributing to the flavor and texture of these products.
• Wine: Leuconostoc oenos (now known as Oenococcus oeni) is involved in malolactic fermentation, a process that converts malic acid to lactic acid, softening the taste of wine.

Pathogenicity

While Leuconostoc species are generally considered non-pathogenic and are safe for use in food production, they can occasionally cause opportunistic infections in humans, particularly in immunocompromised individuals. Such infections may include bacteremia, endocarditis, and meningitis.

Identification

Leuconostoc species can be identified through a combination of phenotypic and genotypic methods, including:

• Gram staining
• Catalase test (Leuconostoc are catalase-negative)
• 16S rRNA gene sequencing

Also see

• Lactic acid bacteria
• Fermentation (food)
• Probiotics
• Lactobacillus
• Streptococcus