Lactic acid bacteria

Lactic acid bacteria (LAB) are a group of Gram-positive bacteria that generate lactic acid as a major metabolic end-product during carbohydrate fermentation. This group of bacteria, comprising genera such as Lactobacillus, Leuconostoc, Pediococcus, Lactococcus, and Streptococcus, are known for their role in the production of fermented foods and beverages.

Classification

LAB are classified under the phylum Firmicutes. They are non-spore forming, non-respiring cocci or rod-shaped bacteria that are characterized by an increased tolerance to a lower pH range. This characteristic is attributed to the production of lactic acid, which is the primary end product of carbohydrate metabolism in these bacteria.

Metabolism

The primary metabolic pathway of LAB is the fermentation of carbohydrates, leading to the production of lactic acid. This process, known as lactic acid fermentation, is what gives fermented foods their distinctive sour taste. Some LAB also produce ethanol and carbon dioxide as by-products of fermentation.

Role in Food Fermentation

LAB play a crucial role in the fermentation of many foods and beverages, including yogurt, cheese, sauerkraut, kimchi, sourdough, and wine. They contribute to the taste, texture, and nutritional value of these products. LAB are also responsible for the preservation of fermented foods, as the lactic acid they produce creates an environment that is inhospitable to spoilage-causing microorganisms.

Health Benefits

LAB are considered probiotics, beneficial bacteria that confer health benefits to the host when consumed in adequate amounts. They can improve digestive health, enhance the immune system, and have been associated with a reduced risk of certain diseases, such as irritable bowel syndrome and certain types of cancer.

See Also

• Fermentation (food)
• Probiotic
• Lactobacillus
• Lactic acid fermentation

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  Streptococci

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  Lactic acid transformation from malic acid