Various definitions currently exist for the term probiotics (Greek pro bios – for life). According to the definition by Fuller 1989, a probiotic is “a preparation of living microorganisms which, after oral application, influences the ratio of intestinal germs in such a way that positive effects on the organism result.” At the European level, the following characterization emerged from a meeting of experts in Brussels on the subject of probiotics in the fall of 1995: “Probiotics are living, defined microorganisms which, after their consumption, exert health-promoting effects that go beyond the level of the basic nutritional-physiological effects. They may be ingested as a food ingredient or in the form of a non-food preparation.” In both definitions, the goal of a probiotic is clear, namely to influence the existing intestinal flora in a way that both enhances well-being and promotes health. The human gut harbors more than 1014 microorganisms. The physiological microbiome is dominated by bacteria, but also consists of organisms such as viruses, animal protozoa and archaea (primordial bacteria). While the small intestine has a relatively low bacterial colonization – it increases from the duodenum and jejunum to the ileum – the large intestine is the intestinal section with the highest bacterial colonization density. The microorganisms of the large intestine (colon) can be assigned to 400 different species. They are an essential part of the “microbiome”, which continues to include bacteria of the skin and urogenital tract, but also of the mouth, throat and nose.Due to the fact that the composition of the intestinal flora is subject to individual variations, about 40 species can be detected regularly. Among the quantitatively most important species are Bacteroides, Eubacterium and Bifidobacterium. The dry mass of the stool consists of 30-75% bacteria. Probiotics contain living microorganisms that exert desirable effects on the intestine. In principle, probiotic germs can come from various sources. However, it has been proven that such bacterial strains, which were originally isolated from the human or animal intestine, are particularly stable. Due to their origin, they are very well adapted to the milieu conditions in the intestine (intestinal tract). Selected lactic acid bacteria, mainly of the genus Lactobacillus and Bifidobacterium, are used as probiotics. Lactic acid bacteria used as probiotics in foods. Lactobacilli
- L. acidophilus
- L. casei
- L. crispatus
- L. delbrueckii subspecies bulgaricus
- L. delbrueckii subspecies lactis
- L. gasseri
- L. helveticus
- L. johnsonii
- L. lactis
- L. paracasei
- L. plantarum
- L. reuteri
- L. rhamnosus
- L. salivarius
Bifidobacteria
- B. adolescentis
- B. animalis
- B. bifidum
- B. breve
- B. infantis
- B. longum
Other
- Enterococcus faecalis
- Enterococcus faecium
- Lactococcus lactis
- Streptococcus thermophilus
- Saccharomyces boulardii
- Sporolactobacillus inulinus
- Bacillus cereus toyoi
- Escherichia coli
Probiotics can be ingested as a component of a food or as a non-food preparation. Most probiotic foods are used in fermented dairy products. Yogurt and yogurt-like products are the most common fermented dairy products consumed in our country. These naturally contain live lactic acid bacteria, primarily lactobacilli and bifidobacteria. Probiotic yogurts are produced according to legal regulations by fermentation – lactic acid fermentation – with Lactobacillus bulgaricus and Streptococcus thermophilus. Both germs mutually favor their growth. Following the fermentation processes, other probiotic bacterial strains can be added to yogurt. In addition to probiotic butter, cheese and curd preparations, probiotic microorganism cultures are also added to other foods. These include baked goods and confectionery, ice cream, breakfast cereals and mueslis, and non-dairy foods such as raw sausages.The influence of fermented meat products, for example raw sausage and vegetables such as sauerkraut and kimchi – lactic fermented vegetables, mainly Chinese cabbage, regularly consumed in Korea – on the human organism has been little studied. Based on common experience, fermented dairy products were known to be a means to long life as early as the end of the 19th century. It is said that “yahurt” – nowadays yogurt – is the secret of people over 100 years old in the Balkans. Moreover, yogurt was used for treatment and prophylaxis of gastrointestinal infectious diseases, for example, diarrheal diseases. The Russian bacteriologist Ilya Metschnikov was the first to investigate the effect of probiotic microorganisms on the human organism using the methods of the time. He was able to show that probiotic germs pass through the digestive tract alive and are excreted in the stool. He assumed that lactic acid bacteria ingested with fermented milk promote health and counteract the process of aging. The prophylactic or therapeutic effect in the intestinal tract of orally ingested microorganisms is subject to various basic conditions. Accordingly, a probiotic bacterial strain should meet the following requirements to be effective:
- Health safety of the probiotic germs. No pathogenic or toxic effects may emanate from their consumption, probiotic cultures therefore have GRAS status – generally recognized as safe.
- Resistance to gastric and bile acids and various digestive enzymes. The probiotic bacterial strains must be able to pass both the stomach – acidic pH due to gastric acid and pepsin as a protein-cleaving enzyme – and the upper small intestine – high concentrations of bile salts and protein-cleaving enzymes from the pancreas (pancreas) without accepting damage.
- Anaerobicity or microaerophilicity – the probiotic organism should be adapted to the low-oxygen conditions in the intestine.
- Attachment capacity (adhesion) to the enterocytes of the intestine as a prerequisite for temporary or permanent colonization of the surface of the intestinal mucosa or intestinal tract. For this purpose, the lactic acid bacteria synthesize special proteins and polysaccharides as adhesion factors.
- Creating ecological niches for their growth. By expressing organic acids, especially lactic acid, and bacteriocins – proteins and low-molecular peptides – the probiotic Lactobacilli and Bifidobacteria can displace existing groups of germs, such as Clostridia, Bacteroides and E. Coli, displace them. In this way, a temporary colonization of the intestine with probiotic bacteria is ensured. Additional administration of prebiotics can promote colonization of the intestine. Prebiotics are non-digestible food components, such as resistant starch and non-starch polysaccharides or dietary fibers, such as oligofructose or inulin. They serve as a selective food base for probiotic bacteria and the intestinal flora and thus specifically stimulate the growth and/or activity of individual or a limited number of positive bacterial strains in the colon. Thus, potentially microorganisms with a health-promoting influence for humans can accumulate in the colon.
- Necessary minimum bacterial count. Since the probiotic effect is dose-dependent, for example, due to the individual constitution of the consumer, type of bacterium – strain specificity – or food texture, and despite the high resistance to the digestive secretions usually only about 10-30% of the consumed probiotic microorganisms reach the colon alive, at least 10 to the power of 6 live germs per g of food product are required.
- The intake of live probiotic cultures with food or as a non-food preparation should be daily to maintain high concentrations of proliferative germs in the large intestine (colon). Only a regular supply of the probiotic microorganisms can provide health benefits. Since probiotic lactobacilli and bifidobacteria can not permanently colonize the intestine, if the oral supply is interrupted, the introduced germs are displaced again after a short time and their number in the feces is reduced.
- Technological suitability.The survivability of probiotic organisms should be guaranteed under the environmental conditions of the food with which they are administered, both before and after fermentation and for the entire period of the declared minimum shelf life in sufficiently high numbers of germs while preserving the probiotic effect.
- Probiotics must be clearly defined in their properties.
- No ability to degrade mucins – organic mucins from the group of glycoproteins -, hemagglutination (agglutination or clumping of blood components) and formation of biogenic amines.
- Demonstrate the postulated health effects for each bacterial culture in the form of appropriate clinical studies in humans. It is important to know that the probiotic effects depend on the particular strain of bacteria (strain specificity). Even closely related bacterial species of the same species may show differences in their physiological effects. Furthermore, the probiotic properties also depend on the type, composition and physical structure of the food consumed.
- Laboratory study of important physiological parameters, such as the activity of the lactose-cleaving enzyme beta-galactosidase – lactase -, intestinal survival and in vivo macrophage stimulation.
Unless the microorganisms used are also to provide fermentation services, they should not affect the sensory properties of the food or not significantly. After consuming probiotic foods, the bacterial strains enter the large intestine (colon) and settle there. They have the ability to multiply and exert various health-related effects.