The Ability of Streptococcus thermophilus BT01 to Modulate Urease Activity in Healthy Subjects' Fecal Samples Depends on the Biomass Production Process.

SCOPE: This study evaluates how manufacturing conditions of probiotic biomass production, using two different cryoprotectants, Cryo-A and Cryo-B, can affect Streptococcus thermophilus BT01 in vivo gastrointestinal tract survival and its ability to modulate the level of urease activity in fecal samples of healthy subjects. METHODS AND RESULTS: A randomized controlled cross-over study is carried out on 20 adult healthy subjects to evaluate total and viable loads, persistence of S. thermophilus BT01, and urease activity in fecal samples. Strain-specific quantification by using developed culture-based method and molecular qPCR tool allows to quantify viable S. thermophilus BT01 strain in 90% of the subjects. The quantification of both total DNA and recovered viable S. thermophilus BT01 in fecal samples does not reveal significant differences between Cryo-A or Cryo-B treated biomass. However, the administration of S. thermophilus BT01 produced with Cryo-A results in a decreased urease activity in fecal samples compared to Cryo-B protected cells. CONCLUSION: This study i) highlights how the manufacturing conditions can play a role in influencing the probiotic functionality in vivo and ii) represents the first evidence that links S. thermophilus to a specific probiotic mechanism, the reduction of urease activity in fecal samples.

In Streptococcus thermophilus, Ammonia from Urea Hydrolysis Paradoxically Boosts Acidification and Reveals a New Regulatory Mechanism of Glycolysis.

Streptococcus thermophilus is widely used in the dairy industry for the manufacturing of fermented milk and cheeses and probiotic formulations. S. thermophilus evolved from closely phylogenetically related pathogenic streptococci through loss-of-function events counterbalanced by the acquisition of relevant traits, such as lactose and urea utilization for the adaptation to the milk environment. In the context of regressive evolution, the urease gene cluster accounts for 0.9% of the total coding sequence belonging to known functional categories. The fate of ammonia and carbon dioxide derived by urea hydrolysis in several biosynthetic pathways have been depicted, and the positive effect of urease activity on S. thermophilus growth fitness and lactic acid fermentation in milk has been already addressed by several authors. However, the mechanistic effect of urea hydrolysis on the energetic metabolisms of S. thermophilus is still unclear. This study aimed to assess the effect of urease activity on the growth and energy metabolism of Streptococcus thermophilus in milk. In milk, 13C-urea was completely hydrolyzed in the first 150 min of S. thermophilus growth, and urea hydrolysis was accompanied by an increase in cell density and a reduction in the generation time. By using energetically discharged cells with gene transcription and translation blocked, we showed that in the presence of fermentable carbon sources, urease activity, specifically the production of ammonia, could dramatically boost glycolysis and, in cascade, homolactic fermentation. Furthermore, we showed that ammonia, specifically ammonium ions, were potent effectors of phosphofructokinase, a key glycolytic enzyme. IMPORTANCE Finding that ammonia-generating enzymes, such as urease, and exogenous ammonia act on phosphofructokinase activity shed new light on the regulatory mechanisms that govern glycolysis. Phosphofructokinase is the key enzyme known to exert a regulatory role on glycolytic flux and, therefore, ammonia as an effector of phosphofructokinase acts, in cascade, modulating the glycolytic pathway. Apart from S. thermophilus, due to the high conservation of glycolytic enzymes in all branches of the tree of life and being aware of the role of ammonia as an effector of phosphofructokinase, we propose to reevaluate the physiological role of the ammonia production pathways in all organisms whose energy metabolism is supported by glycolysis.

Streptococcus thermophilus: To Survive, or Not to Survive the Gastrointestinal Tract, That Is the Question!

The probiotic market is increasing world-wide as well as the number of products marketed as probiotics. Among the latter, many products contain Streptococcus thermophilus strains at several dosages. However, the scientific evidence that should support the probiotic status of those S. thermophilus strains is often contradictory. This review analyses the scientific literature aimed to assess the ability of S. thermophilus strains to survive the human gastrointestinal tract by discussing the scientific validity of the methods applied for the bacterial recovery and identification from stool samples. This review highlights that in most of the intervention studies reviewed, the identification of S. thermophilus strains from stools was not carried out with the necessary taxonomic accuracy to avoid their misidentification with Streptococcus salivarius, a common human commensal and a species phylogenetically close to S. thermophilus. Moreover, this review highlights how critical the accurate taxonomic identification of S. thermophilus in metagenomics-based studies can be.

The exploitation of cornelian cherry (Cornus mas L.) cultivars and genotypes from Montenegro as a source of natural bioactive compounds.

Cornelian cherry (CC) fruits a source of bioactive compounds that are still being underutilized. In this study, a comprehensive characterization of 11 Montenegrin CC local or introduced genotypes and cultivars collected in the wild or from organic orchards is provided. Their potential utilizations as natural antioxidants, colorants and organic food ingredients were exploited. CC fruits had high level of vitamin C (48-108 mg/100 g), malic acid (104-375 mg/100 g), and total polyphenols (158-591mgGAE/100 g). They also displayed high antioxidant activity based on DPPH (623-1903µmolTE/100 g), ABTS (441-1475µmolTE/100 g), and FRAP (1509-5954µmolFe2+/100 g) assays. UHPLC-PDA-HESI-MS/MS analyses were used to quantify the concentration of phenolic acids (7.69-19.87 mg/100 g), flavonoids (10.87-44.34 mg/100 g), anthocyanins (11.85-195.43 mg/100 g) and iridoids (129.07-341.20 mg/100 g). For each of this groups, the most abundant were caftaric acid (12.24 mg/100 g), quercetin 3-glucuronide (29.66 mg/100 g), cyanidin 3-O-galactoside (130.93 mg/100 g) and loganic acid (303.3 mg/100 g), respectively. PCA and cluster heatmap analysis highlighted potentials for further exploitation of local genotypes and cultivars through organic food processing and breeding program.

Design of potential probiotic yeast starters tailored for making a cornelian cherry (Cornus mas L.) functional beverage.

We carried out a step-by-step accurate procedure to design yeast starters with probiotic and technological traits to ferment cornelian cherry fruits puree (CP). Pichia kudriavzevii DCNa1 and Wickerhamomyces subpelliculosus DFNb6 were selected as binary starters due to their metabolic traits and low ethanol yield. Fermentation by selected starters positively affected the physical stability of CP. Depletion of loganic and cornuside acids during CP fermentation, leads us to speculate that yeasts might be involved in the conversion of iridoids to bioactive derivatives. Compared to unfermented CP, fermentation also affected the profile of CP volatiles, resulting in higher amount of alcohols and esters, and lower levels of aldehydes and alkanes. Viable cell number of selected yeasts in CP after 21 days of storage at 4 °C as well as after in vitro simulated digestion remained above the minimum dose recommended for a probiotic beverage. Under the in vitro gastrointestinal batch simulating the digestion process, we provided original evidence about the ability of yeasts conveyed by fermented CP to modulate the intestinal microbiota. We also faced some issues related to the yeasts physiology and the link between biofilm and cell viability that still deserve to be more in depth investigated.