Acquisition of PrtS in Streptococcus thermophilus is not enough in certain strains to achieve rapid milk acidification

International audienceAbstractThe acquisition of prtS by Streptococcus thermophilus strains allowed hydrolysis of caseins into peptides and then to increase their growth in milk. This leads to faster milk acidification, which is important in dairy industry. However, some strains harboring the same allele of prtS present different acidification rates, which could be explained by a difference in the regulation of prtS expression. We chose two strains with the same allele of prtS (including the same promoter region): one, PB302, is with high acidification rate while the other, PB18O, is without. They exhibited similar growth in M17, but not in milk, where PB302 showed better growth. The expression of prtS and activity of PrtS were lower in PB18O, in the two media tested. We demonstrated that other genes known to be involved in carbon and nitrogen metabolism were overexpressed in PB302. Interestingly, these genes were overexpressed in milk compared to M17. Nearly all these genes possessed a putative CodY-box in their promoter region. Taken together, difference of gene expression detected in PB302 between milk (low-peptide medium) and M17 (rich-peptide medium) and presence of a putative CodY-box is a feature of the transcriptional pattern of CodY-regulated genes. Altogether, our results propose that acquisition of prtS is not enough in certain strains to achieve rapid milk acidification. High transcriptional level of dtpT, amiF, ilvC, ilvB, bcaT, livJ, ackA, codY, and prtS in fast acidifying strain suggests that this transcriptional pattern could be required for fast milk acidification in Streptococcus thermophilus

<i>Streptococcus thermophilus</i>: A Source of Postbiotics Displaying Anti-Inflammatory Effects in THP 1 Macrophages

In addition to traditional use in fermented dairy products, S. thermophilus also exhibits anti-inflammatory properties both in live and heat-inactivated form. Recent studies have highlighted that some hydrolysates from surface proteins of S. thermophilus could be responsible partially for overall anti-inflammatory activity of this bacterium. It was hypothesized that anti-inflammatory activity could also be attributed to peptides resulting from the digestion of intracellular proteins of S. thermophilus. Therefore, total intracellular proteins (TIP) from two phenotypically different strains, LMD-9 and CNRZ-21N, were recovered by sonication followed by ammonium sulphate precipitation. The molecular masses of the TIP of both strains were very close to each other as observed by SDS-PAGE. The TIP were fractionated by size exclusion fast protein liquid chromatography to obtain a 3–10 kDa intracellular protein (IP) fraction, which was then hydrolysed with pancreatic enzyme preparation, Corolase PP. The hydrolysed IP fraction from each strain exhibited anti-inflammatory activity by modulating pro-inflammatory mediators, particularly IL-1β in LPS-stimulated THP-1 macrophages. However, a decrease in IL-8 secretion was only observed with hydrolysed IP fraction from CNRZ-21N, indicating that strain could be an important parameter in obtaining active hydrolysates. Results showed that peptides from the 3–10 kDa IP fraction of S. thermophilus could therefore be considered as postbiotics with potential beneficial effects on human health. Thus, it can be used as a promising bioactive ingredient for the development of functional foods to prevent low-grade inflammation

Cell Proteins Obtained by Peptic Shaving of Two Phenotypically Different Strains of <i>Streptococcus thermophilus</i> as a Source of Anti-Inflammatory Peptides

Streptococcus thermophilus, a food grade bacterium, is extensively used in the manufacture of fermented products such as yogurt and cheeses. It has been shown that S. thermophilus strains exhibited varying anti-inflammatory activities in vitro. Our previous study displayed that this activity could be partially due to peptide(s) generated by trypsin hydrolysis of the surface proteins of S. thermophilus LMD-9. Surface protease PrtS could be the source of these peptides during gastrointestinal digestion. Therefore, peptide hydrolysates were obtained by shaving two phenotypically distinct strains of S. thermophilus (LMD-9 PrtS+ and CNRZ-21N PrtS−) with pepsin, a gastric protease, followed or not by trypsinolysis. The peptide hydrolysates of both strains exhibited anti-inflammatory action through the modulation of pro-inflammatory mediators in LPS-stimulated THP-1 macrophages (COX-2, Pro-IL-1β, IL-1β, and IL-8) and LPS-stimulated HT-29 cells (IL-8). Therefore, peptides released from either PrtS+ or PrtS− strains in the gastrointestinal tract during digestion of a product containing this bacterium may display anti-inflammatory effects and reduce the risk of inflammation-related chronic diseases

The X-prolyl dipeptidyl-peptidase PepX of Streptococcus thermophilus initially described as intracellular is also responsible for peptidase extracellular activity

International audienc

Streptococcus thermophilus, an emerging and promising tool for heterologous expression: Advantages and future trends

[i]Streptococcus thermophilus[/i] is the second most used bacterium in dairy industry. It is daily consumed bymillions of people through the worldwide consumption of yogurts, cheeses and fermented milks.[i]S. thermophilus[/i] presents many features that make it a good candidate for the production of heterologousproteins. First, its ability to be naturally transformable allows obtaining swiftly and easily recombinantstrains using various genetic tools available. Second, its Generally Recognised As Safe status and its abilityto produce beneficial molecules or to liberate bioactive peptides from milk proteins open up the way forthe development of new functional foods to maintain health and well-being of consumers. Finally, itsability to survive the intestinal passage and to be metabolically active in gastrointestinal tract allowsconsidering[i] S. thermophilus[/i] as a potential tool for delivering various biological molecules to thegastrointestinal tract.The aim of this review is therefore to take stock of various genetic tools which can be employed in[i]S. thermophilus[/i] to produce heterologous proteins and to highlight the advantages and future trends ofuse of this bacterium as a heterologous expression host

Importance of digestive mucus and mucins for designing new functional food ingredients

International audienceThe mucus, mainly composed of the glycoproteins mucins, is a rheological substance that covers the intestinal epithelium and acts as a protective barrier against a variety of harmful molecules, microbial infection and varying lumen environment conditions. Alterations in the composition or structure of the mucus could lead to various diseases such as inflammatory bowel disease or colorectal cancer. Recent studies revealed that an exogenous intake of probiotic bacteria or other dietary components (such as bioactive peptides and probiotics) derived from food influence mucus layer properties as well as modulate gene expression and secretion of mucins. Therefore, the use of such components for designing new functional ingredients and then foods, could constitute a novel approach to preserve the properties of mucus. After presenting some aspects of the mucus and mucins in the gastrointestinal tract as well as mucus role in the gut health, this review will address role of dietary ingredients in improving mucus/mucin production and provides new suggestions for further investigations of how dietary ingredients/probiotics based functional foods can be developed to maintain or improve the gut health

In Vitro Anti-Inflammatory Activity of Peptides Obtained by Tryptic Shaving of Surface Proteins of <i>Streptococcus thermophilus</i> LMD-9

Streptococcus thermophilus, a lactic acid bacterium widely used in the dairy industry, is consumed regularly by a significant proportion of the population. Some strains show in vitro anti-inflammatory activity which is not fully understood. We hypothesized that peptides released from the surface proteins of this bacterium during digestion could be implied in this activity. Consequently, we prepared a peptide hydrolysate by shaving and hydrolysis of surface proteins using trypsin, and the origin of peptides was checked by liquid chromatography–tandem mass spectrometry (LC-MS/MS) analysis. Most of the identified peptides originated from bacterial cell surface proteins. The anti-inflammatory activity of peptide hydrolysate was investigated under inflammatory conditions in two cell models. Peptide hydrolysate significantly decreased secretion of pro-inflammatory cytokine IL-8 in lipopolysaccharide (LPS)-stimulated human colon epithelial HT-29 cells. It also reduced the production of pro-inflammatory cytokines IL-8, IL-1β and the protein expression levels of Pro-IL-1β and COX-2 in LPS-stimulated THP-1 macrophages. The results showed that peptides released from bacterial surface proteins by a pancreatic protease could therefore participate in an anti-inflammatory activity of S. thermophilus LMD-9 and could prevent low-grade inflammation

Importance of digestive mucus and mucins for designing new functional food ingredients

International audienc

Streptococcus thermophilus: From yogurt starter to a new promising probiotic candidate?

International audienceProbiotics are defined as live microorganisms that when administered in adequate amount confer a health benefit to the host. To be considered as a probiotic, a bacterial strain must not only be safe but should also survive in the human gastrointestinal tract and exert health benefits on its host. Streptococcus thermophilus is a Gram positive bacterium widely used in dairy fermentations for the production of yogurt and cheese. In contrast with other lactic acid bacteria, the probiotic status of S. thermophilus remains still questioned. This review gives an update of the human trials, in vivo assays in animal models and in vitro experiments, which have assessed the resistance of S. thermophilus to gastrointestinal stresses and have investigated its positive health effects. The underlying mechanisms of action are also described and the probiotic status of the bacterium is debated with respect to the available literature

Strategies of producing bioactive peptides from milk proteins to functionalize fermented milk products

16th World Congress of the International-Union-of-Food-Science-and-Technology (IUFoST), Foz do Iguacu, BRAZIL, AUG 05-09, 2012International audienceBesides their basic nutritional role, dietary proteins contain bioactive peptides which are encrypted in their sequence and may modulate different body functions such as digestive, cardiovascular, immune and nervous systems, and therefore contribute in maintaining consumer health. Currently, milk proteins are considered to be the major source of bioactive peptides. The occurrence of these peptides has already been reported in fermented milk products such as yogurt, sour milk or kefir and some of them have been shown to confer health benefits. This review focuses on different strategies that could be employed to enhance the production of bioactive peptides from the milk proteins that will be consequently used to functionalize the fermented milk products. Three types of strategies are developed. The first exploits the proteolytic system of lactic acid bacteria (LAB) or food grade enzymes or combination of both to release the functional peptides from the milk proteins directly in the fermented milk products. The second concerns the supplementation of the fermented milk products with the bioactive peptides obtained outside of the product through the hydrolysis of the purified proteins by the same enzyme sources. Finally, the last consists in the production of the bioactive peptides, initially identified from the milk-proteins, by microorganisms using recombinant DNA technology