Lactobacillus (pl. Lactobacilli), a genus from the phylum Firmicutes, are gram-positive facultative anaerobic or microaerophilic rod-shaped bacteria. Lactobacilli make up a significant portion of the lactic acid bacteria (LAB) group. Lactobacillus spp. are naturally found in the human gut and vaginal microbiota. In addition, these bacteria and are often found in probiotic products, like yogurt, and are used to help maintain a healthy gut. Scientists recognize and have sequenced over 50 known species.

In general, strains of Lactobacillus are considered safe because they are naturally found in the human microbiome and in fermented foods like kimchi, cottage cheese, and kefir. Lactobacillus also have low pathogenic potential, which further reinforces their safety.

Lactobacillus in Probiotics, Biotherapies and Disease States

Some strains of Lactobacillus spp. and other LAB may possess potential therapeutic properties, including anti-inflammatory properties and anti-cancer inhibitors, which has been demonstrated in several studies in rodents.

Lactobacillus spp. can also be used to restore balance within the vaginal and gut microbiome. Studies suggest that Lactobacillus protect the vaginal wall and help to maintain an acidic environment. In addition, Lactobacillus spp. are critical to the production of hydrogen peroxide, an effective antibiotic.

Some Lactobacillus secrete peptide, a hormone that releases insulin. Interestingly enough, one strain may prove effective in type 2 diabetes therapies for rodents by transferring insulin control from the pancreas to the upper intestines. Further testing is currently underway to determine whether higher dosages of Lactobacillus can completely reverse type 2 diabetes in rodents. Scientists are unsure of whether this translates to humans or not.

Dental caries

Tooth decay is often caused by streptococci bacteria, including Streptococcus mutans; however, some Lactobacillus spp. have also been linked to dental caries. Although Lactobacillus spp. are typically beneficial to the human microbiome, lactic acid can corrode teeth. The Lactobacillus count in saliva has been utilized in caries markers effectively for many years.

Contradictory evidence from studies has demonstrated that some Lactobacillus spp. are actually beneficial in the oral cavity and for dental health, preventing pathogens like Streptococcus spp. from dental decay. Research on Lactobacillus and its correlation to oral health may open the door to new dental therapies to prevent common diseases.

Food production and spoilage

Starter cultures for controlled fermentation of yogurt, sauerkraut, cheese, pickles, wine, beer, kimchi, kefir and other fermented foods often include Lactobacillus species, which rely on the production of bacteriocins and other compounds for antibacterial and anti-fungal activity. In many traditional vegetable fermentation, vegetables are submerged in brine, and salt-tolerant Lactobacillus species feed on natural sugars found in the vegetables. The bacteria metabolize sugars into lactic acid, lowering the pH of their environment and creating a signature "sourness" associated with yogurt, sauerkraut, etc. The combination of salt and lactic acid creates an extremely hostile environment and prevents the growth of fungus and other bacteria, preserving the vegetables.

Sourdough bread relies on Lactobacillus spp. and yeast. As flour mixes with water to make the starter dough. Enzymes in the flour split starches into sugars. Multitudes of yeast an bacteria grow rapidly and converge on the sugars. Once the Lactobacilli convert sugars to lactic acid, the dough’s pH drops to around 3.8. Most microbes perish at this point, but yeasts that are capable of surviving convert the sugars into carbon dioxide and ethanol.

Lactobacillus, especially L. casei and L. brevis, are often the bacteria connected to beer spoilage. They are, however, essential to the production of American Wild Ales and Belgian Lambics, and other sour beers with a distinct tart flavor.


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