What do the bacteria in probiotics do?

Probiotics are various preparations or products that contain living microorganisms such as lactic acid bacteria or yeasts and promote health, especially in the gut. The word probiotics means "for life" - from the Latin word pro "for" and the ancient Greek word bios "life".

Our gut is home to many different bacteria (more than 1000 different species) that have adapted to the living conditions there. This community of bacteria is called the microbiome. The microbiome contributes to good intestinal function. The composition of the microbiome plays a major role in this. Good bacteria support digestion, e.g. by producing important metabolites such as vitamins.

In addition, an overabundance of good bacteria prevents pathogenic bacteria from colonising, and in recent years the importance of intestinal bacteria for our health has been increasingly researched. Not only does digestion benefit from a healthy gut, other areas of the body are also positively influenced by a balanced and intact microbiome, such as mental health.

Probiotic products with appropriate bacteria can support intestinal health with different mechanisms of action. Probiotics help to rebuild the intestinal flora, especially if the balance of intestinal bacteria has been upset by illness, malnutrition, stress or antibiotic treatment: on the one hand, they can produce substances that inhibit the growth of undesirable, pathogenic bacteria and thus prevent them from spreading in the intestine. Probiotics can also promote the immune defence of the body's own cells or lower the pH value in the intestine and thus create an environment in the intestine that in turn supports the balance of the microbiome. Some probiotics produce enzymes that break down indigestible food components into usable components.

An important property of probiotic bacteria is that they survive the gastrointestinal passage due to their resistance to stomach acid and can then develop their effect in the intestine. Lactobacilli (lactic acid bacteria) can tolerate the low pH value in the stomach. Other probiotics such as Bacillus subtilis can form resistant permanent forms (spores) that are also resistant to gastric juice.

However, probiotic properties are not only found in food additives or medicines, but are also characteristic of some foods. Fermented foods in particular contain many microorganisms. Fermentation - i.e. the conversion of complex substances by microbial enzymes into acids, gases or alcohols - often makes foods last longer, are easier to digest and rich in vitamins. Sauerkraut, for example, contains lactic acid bacteria and can promote intestinal health as a natural probiotic. In Japan, there is also a traditional fermented food made from soya beans called natto, which contains the bacterium Bacillus subtilis ssp. natto. It is said to have a positive effect on health.

Yoghurt can also contain lactic acid bacteria such as Lactobacillus bulgaricus, which have a positive effect on the gut as described above. The bacterial cultures are added as starter cultures during yoghurt or cheese production.

Probiotics are often combined with prebiotics. These are indigestible food components, usually carbohydrates, which specifically promote the growth of certain positive intestinal bacteria. The combination of prebiotics and probiotics is intended to unite the beneficial effects of both components in one product.


Lactic acid bacteria (Lactobacillus) under the microscope (Source: A. Grüppen)


Read more:

Probiotika und Präbiotika: Gutes für den Darm: https://www.ndr.de/ratgeber/gesundheit/Probiotika-und-Praebiotika-Darmflora-aufbauen,darmgesundheit100.html

Lactobacillus – Alleskönner für die Gesundheit: https://www.biospektrum.de/magazinartikel/lactobacillus-alleskoenner-fuer-die-gesundheit?dl=1

Bacillus subtilis – ein Multitalent der industriellen Biotechnologie: https://www.biospektrum.de/magazinartikel/bacillus-subtilis-ein-multitalent-der-industriellen-biotechnologie?dl=1


Text and Figures: Anika Grüppen, anika.grueppen[at]evonik.com, use according to  CC 4.0