In this essay work, the ability of probiotic biofi lm formation on carrier surface was demonstrated. Probiotic biofi lms exhibit the same properties as pathogen microbial biofi lms but with higher resistance to low pH values and bile salts. The ability of different probiotic strains (Lactobacillus acidophilus, Bifi dobacterium breve, Bifi dobacterium longum) to interact with pre-selected carriers divided into 3 categories (polymers, complex food matrices, and inorganic compounds) was tested. Lactobacillus acidophilus and Bifi dobacterium longum combined with inorganic silica carrier exhibited the interaction leading to biofi lm formation only. Prepared biofi lm (Lactobacillus acidophilus) was then subjected to comparative study with planktonic bacterial culture. The ability to survive in the presence of low pH value (pH 1-3) and bile salts (0.3% solution) was evaluated. Low pH value (pH 1) had a harsh effect on free cell culture causing decreased cell viability (71.9±3.2% of viable cells). Biofi lm culture exhibited higher resistance to low pH value, the viability exceeded 90%. The exposure of free cell probiotic culture to porcine bile resulted in an almost constant decrease in viability during the study period (68.2±1.1% of viable cells, after 240 min incubation). Viability of biofi lm after the exposition to bile was almost constant with a slight decrease of no more than 5% during the study.Keywords: probiotics, biofi lm, carrier, acid tolerance, bile toleranceThe fi rst mention of probiotics appeared at the beginning of the 20 th century in the writings of Elie Metchnikoff. He suggested that the longevity and healthy life of Bulgarian people is hidden in their consumption of fermented milk products (TRIPATHI & GIRI, 2014). In 2001, probiotics as "live microorganisms, which when administered in adequate amounts confer a health benefi t on the host" (FAO/WHO, 2001) was defi ned.During the last 15-20 years, it was recognized that the developmental process of biofi lm formation is the natural way of life for microorganisms, without differences between harmful and commensal microorganisms. Therefore, on one hand, biofi lm formation is an important clinical pathogenic mechanism, a menace to the aging population, immunocompromised and poly-traumatic patients, on the other hand, a modern medical instrumental intervention (RÖMLING et al., 2014). In the common line, biofi lm cells have a higher resistance to antimicrobial agents and agents harmful to microbes in biofi lm than planktonic bacteria. The formation of a barrier or biofi lm prohibits the direct contact with harmful agents (SREY et al., 2013). * To whom correspondence should be addressed. Phone: +420 736 468 302; e-mail: grossova@favea.czThis is an open-access article distributed under the terms of the Creative Commons Attribution 4.0 License, which permits unrestricted use, distribution, and reproduction in any medium for non-commercial purposes, provided the original author and source are credited.

The aim of this study was to evaluate the influence of model (alcohol, sugar, salt, protein and acid) and real foods and beverages on the viability of probiotics during incubation and artificial digestion. Viability of monocultures Lactobacillus acidophilus CCM4833 and Bifidobacterium breve CCM7825T, and a commercial mixture of 9 probiotic bacterial strains, was tested by cultivation assay and flow cytometry. In model foods, the best viability was determined in the presence of 0.2 g/L glucose, 10% albumin and 10% ethanol. As the most suitable real food for probiotic survival, complex protein and carbohydrate substrates were found, such as beef broth, potato salad with pork, chicken with rice, chocolate spread, porridge and yoghurt. The best liquid was milk and meat broth, followed by Coca-Cola, beer and coffee. Viability of probiotics was higher when consumed with meals than with beverages only. Addition of prebiotics increased the viability of probiotics, especially in presence of instant and fast foods. Generally, the highest viability of probiotics during artificial digestion was observed in mixed culture in the presence of protein, sugar and fat, or their combination. The increase of cell viability observed in such foods during model digestion may further contribute to the positive effect of probiotics on human health.

The current market of probiotic supplements is significantly growing although the quality and effectiveness of the commonly sold products are variable. Parameters such as the composition of each individual microbiota, strain specificity, production procedures, or storage can influence the potential positive outcome of probiotic supplements on consumers. The aim of this study was to determine changes of selected markers within the microbiota after 3 months treatment by the personalized probiotic supplement. Stool samples of 48 volunteers were analyzed by 16s ribsosomal RNA sequencing. The composition (selection of species, number of species used, and number of colony-forming units) of the probiotic mixture was designed based on the gut microbiota analysis and it was prepared for each patient separately. After 3 months of probiotic supplementation, a control sample was analyzed. Data confirmed a statistically significant increase in abundance of genera Lactobacillus and Bifidobacterium and phylum Actinobacteria. The overall number of species was also increased thus increasing the overall diversity of the microbiota, which is considered a marker of healthy gut microbiota.

The aim was to evaluate the influence of model (alcohol, sugar, salt, protein and acid) and real foods and beverages on the viability of probiotics during incubation and artificial digestion. Viability of monocultures Lactobacillus acidophilus CCM4833 and Bifidobacterium breve CCM7825T and commercial mixture of 9 probiotic bacterial strains were tested by cultivation assay and flow cytometry. In model foods, the best viability was determined in the presence of 0.2 g/L glucose, 10% albumin and 10% ethanol. As the most suitable real food for probiotic survival complex protein and carbohydrate substrates were found, such as beef broth, potato salad with pork, chicken with rice, chocolate spread, porridge and yoghurt. The best liquid was milk and meat broth, followed by coca-cola, beer and coffee. Viability of probiotics was higher when consumed with meals than with beverages only. Addition of prebiotics increased the viability of probiotics especially in presence of instant and fast foods. Generally, the highest viability of probiotics during artificial digestion was observed in mixed culture in presence of protein, sugar and fat or their combination. The increase of cell viability observed in such foods during model digestion may further contribute to the positive effect of probiotics on human health.