Lactobacillus fermentum is a species of bacteria that populates a wide array of fermented foods. As a member of the lactic acid bacteria group, it plays a role in the production of these foods and is studied for its probiotic characteristics. This bacterium is integral to creating the distinct properties of certain foods and is also naturally found in the human body.
What is Lactobacillus fermentum?
Lactobacillus fermentum is a Gram-positive bacterium, meaning it retains a specific stain in laboratory tests due to its cell wall structure. Morphologically, it is rod-shaped and can exist as a facultative anaerobe, capable of surviving with or without oxygen. This adaptability allows it to thrive in diverse environments, from the human gastrointestinal tract to fermenting plant matter.
Classified as a heterofermentative organism, L. fermentum produces lactic acid, carbon dioxide, and other compounds from sugars. This metabolic activity is distinct from homofermentative bacteria, which primarily produce lactic acid. Strains of this bacterium are considered probiotics—live microorganisms that may confer health benefits when consumed in adequate amounts. Its ability to survive the acidic conditions of the stomach and bile in the intestines enables its probiotic function.
Discovering Lactobacillus fermentum in Your Diet
This bacterium is a common inhabitant of many fermented foods. A well-known source is sourdough bread, where L. fermentum is often a component of the starter culture. It works alongside wild yeasts to leaven the bread and contribute to its characteristic tangy flavor and texture.
Beyond bakeries, L. fermentum is found in certain dairy products. While not always a primary starter culture, it can be present in some yogurts, kefirs, and specific types of cheese as part of the microbial community that develops during aging.
Fermented vegetables are another significant dietary source. It is involved in the wild fermentation of cabbage to make sauerkraut and kimchi, as well as in the brine for pickles, where it helps preserve the vegetables and develop their taste. Some traditionally fermented meats and sausages may also rely on this or related lactic acid bacteria for preservation and flavor development.
How Lactobacillus fermentum Transforms Foods
The primary mechanism by which Lactobacillus fermentum alters food is lactic acid fermentation. The bacterium metabolizes carbohydrates in raw ingredients, such as flour or vegetable sugars, and produces lactic acid as a byproduct. This increase in acidity lowers the pH of the food, creating an environment that inhibits the growth of spoilage-causing microorganisms, thus acting as a natural preservative. This acidification is also directly responsible for the tangy or sour taste found in foods like sourdough and sauerkraut.
In addition to preservation and flavor, L. fermentum contributes to changes in food texture. In sourdough bread, the acids it produces modify gluten proteins, which can affect the final crumb structure and chewiness. In some dairy applications, the metabolic activity of lactic acid bacteria contributes to the coagulation of milk proteins, a step in making yogurt and cheese. The bacterium also generates other compounds, including alcohols and esters, which contribute to the complex aroma of the final product.
Nutritional and Health Significance in Foods
Consuming foods containing Lactobacillus fermentum introduces this probiotic bacterium into the digestive system, where it can contribute to the balance of the gut microbiota. A diverse and balanced gut microbiome is associated with overall digestive health, and these bacteria can help support the existing community of beneficial microbes.
The fermentation process itself improves the digestibility of certain foods. In sourdough bread, the activity of L. fermentum can help pre-digest some complex carbohydrates and proteins, potentially making the bread easier to digest. In dairy products, lactic acid bacteria convert lactose into lactic acid, which can be beneficial for individuals with lactose intolerance.
This bacterial activity can also enhance the bioavailability of nutrients. The breakdown of phytates in fermented grains by L. fermentum can improve the body’s ability to absorb minerals like iron, zinc, and calcium. Furthermore, some strains of lactic acid bacteria can synthesize certain B vitamins, increasing the nutritional value of the fermented product. The presence of these bacteria in the gut is also linked to the modulation of the immune system through interaction with gut-associated lymphoid tissue.