Abstract
Yogurt is a traditional fermented dairy product, prepared with starter cultures containing Streptococcus thermophilus and Lactobacillus bulgaricus that has gained widespread consumer acceptance as a healthy food. It is widely accepted that yogurt cultures have been recognized as probiotics, due to their beneficial effects on human health. In this study, we have characterized technological and health-promoting properties of autochthonous strains S. thermophilus BGKMJ1-36 and L. bulgaricus BGVLJ1-21 isolated from artisanal sour milk and yogurt, respectively, in order to be used as functional yogurt starter cultures. Both BGKMJ1-36 and BGVLJ1-21 strains have the ability to form curd after five hours at 42 °C, hydrolyze αs1-, β-, and κ- casein, and to show antimicrobial activity toward Listeria monocytogenes. The strain BGKMJ1-36 produces exopolysaccharides important for rheological properties of the yogurt. The colonies of BGKMJ1-36 and BGVLJ1-21 strains that successfully survived transit of the yogurt through simulated gastrointestinal tract conditions have been tested for adhesion to intestinal epithelial Caco-2 cells. The results reveal that both strains adhere to Caco-2 cells and significantly upregulate the expression of autophagy-, tight junction proteins-, and anti-microbial peptides-related genes. Hence, both strains may be interesting for use as a novel functional starter culture for production of added-value yogurt with health-promoting properties.
Highlights
Yogurt is popular dairy product obtained by fermentation of lactose to lactic acid by lactic acid bacteria (LAB), and can be made from all types of milk [1,2]
The interest of the dairy industry in production of fermented dairy products is the selection and use of LAB that converts lactose to lactic acid, degrades casein, and produces EPS and antimicrobial compounds, such as organic acids, hydrogen peroxide, antifungal peptides, and bacteriocins [55]
Proteolytic activity of yogurt cultures leads to the production of free amino acids, which may be converted to various flavor compounds, such as ammonia, amines, aldehydes, phenols, indole, and alcohols, all of them contributing to yogurt flavor [3]
Summary
Yogurt is popular dairy product obtained by fermentation of lactose to lactic acid by lactic acid bacteria (LAB), and can be made from all types of milk [1,2]. Bulgaricus that are responsible for formation of typical yogurt flavor during sugar fermentation (glycolysis), proteins degradation (proteolysis), and fat degradation (lipolysis) [3]. They produce exopolysaccharides (EPSs) that provide viscous texture of yogurt, and have a beneficial effect on the consumer’s health [4]. Besides the presence of S. thermophilus and L. bulgaricus in starter cultures, yogurt-like products may contain other LAB strains with functional probiotic properties [6]. Recent data showed that LAB-associated biomolecules and metabolites could trigger autophagy [21,22,23], an important mechanism of cell recycling, required for anti-microbial protection, gut ecology regulation, appropriate intestinal immune response, and maintenance of epithelial barrier integrity [24]. Having in mind that all of these processes are regulated by autophagy, its modulation by LAB could represent a new strategy in maintenance of intestinal mucosal physiology
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