Lactobacillus

Lactobacillus is a genus of Gram-positive, non-spore-forming, rod-shaped bacteria that produce lactic acid as the main end product of carbohydrate fermentation. They are generally aerotolerant anaerobes or microaerophiles and are characterized by their role in fermentation rather than strict oxygen requirements. Many species are homofermentative (producing primarily lactic acid) while others are heterofermentative, yielding lactic acid along with other metabolites such as carbon dioxide or ethanol.

Taxonomically, Lactobacillus has been a large and diverse group of lactic acid bacteria. In recent years, molecular reclassification split many species into several new genera, so the name Lactobacillus now refers to a subset of species rather than the entire former group. In practical terms, the term is still widely used in food labeling and probiotic products, although scientific databases may assign species to newly created genera.

Lactobacilli occur in the human and animal gastrointestinal tracts, the vaginal mucosa, on plant surfaces, and in a broad range of fermented foods. They are key players in the production of yogurt, cheese, kefir, sourdough, sauerkraut, pickles, and other fermented vegetables, contributing acidity, flavor, and texture to these products.

Metabolic and functional roles include acidification of environments that inhibits spoilage organisms and some pathogens. Many strains produce bacteriocins and exopolysaccharides, which can enhance safety and texture in foods. Some strains are promoted as probiotics to support gut health and immune function, though effects are highly strain-specific.

Most Lactobacillus species are considered safe and are widely used in foods and dietary supplements. Rare infections can occur, particularly in individuals with compromised health, underscoring the importance of proper strain selection and quality control.