BACKGROUND AND OBJECTIVE: Microbial selenium (Se) supplementation is an essential area of biotechnological research due to differences in the bioavailability and toxicity of different forms of selenium. To date, research has focused mainly on the use of selenized yeast. However, in recent years, scientific interest has also increased in other microorganisms, such as lactic acid bacteria (LAB), which have several unique properties that can affect the quality and bioavailability of selenium. LAB, unlike yeast, can also act as probiotics, which may bring additional health benefits related to improving the intestinal microbiota and supporting the health of the gastrointestinal tract. METHODS: This study investigates the in vitro bioaccessibility and bioavailability of Se from two lactic acid bacterial strains, Streptococcus thermophilus CCDM 144 and Enterococcus faecium CCDM 922 A. We evaluated Se accumulation, speciation, and stability during simulated gastrointestinal digestion and Se permeation through a Caco-2 cell monolayer model. RESULTS: Both strains accumulated Se, metabolizing it predominantly into selenium nanoparticles (SeNPs, 64-77 % of total Se), with only a minor fraction (<5 % of total Se) of organic Se species. Experiments revealed that while organic Se species had high bioavailability (up to 90 %), their bioaccessibility during digestion was very low (<0.1 % of total Se). In contrast, SeNPs showed high bioaccessibility (∼90 %) and moderate transport efficiency through the intestinal model (16-19 % after 4 hours). CONCLUSION: These results highlight the potential of SeNPs produced by lactic acid bacteria as a bioaccessible form of Se for dietary supplementation. Further research is required to explore the behavior of SeNPs within the human body to fully understand how they can be used safely and effectively in nutrition or other applications.
- MeSH
- biologická dostupnost * MeSH
- biologické modely MeSH
- Caco-2 buňky MeSH
- funkce střevní bariéry MeSH
- Lactobacillales metabolismus MeSH
- lidé MeSH
- permeabilita MeSH
- selen * metabolismus MeSH
- Streptococcus thermophilus metabolismus MeSH
- trávení MeSH
- Check Tag
- lidé MeSH
- Publikační typ
- časopisecké články MeSH
In this study, a method combining Raman spectroscopy with chemometric analysis was developed for detection of phage presence in raw milk and discrimination of Streptococcus thermophilus and Lactobacillus bulgaricus phages which are among the main phages causing problems in dairy industry. For this purpose, S. thermophilus and L. bulgaricus phages were added into raw milk separately, and then some pretreatments such as fat separation, removal of casein, and filtration were applied to the raw milk samples. Raman spectra of the samples were collected and then analyzed using principal component analysis in order to discriminate these phages in raw milk. In the next step, dilutions of S. thermophilus phages in pretreated raw milk were prepared, and Raman spectra were collected. These spectra were analyzed by using partial least squares method to quantify phages in low titer. Consequently, it has been demonstrated that S. thermophilus and L. bulgaricus phages, which have titers sufficient to fail the fermentation (~ 107 pfu/mL) and have lower titers (102-103 pfu/mL), could be discriminated from antibiotic and each other. Additionally, low concentrations of S. thermophilus phages (102 pfu/mL) could be detected through Raman spectroscopy with a short analysis time (60 min) and high coefficient of determination (R2) values for both calibration (0.985) and validation (0.906) with a root mean square error of calibration of 70.54 and root mean square error of prediction of 165.47. However, a lower success was achieved with L. bulgaricus phages and the obtained coefficient of determination values were not sufficiently high (0.649).
- MeSH
- analýza hlavních komponent MeSH
- bakteriofágy klasifikace fyziologie MeSH
- fermentace MeSH
- Lactobacillus delbrueckii virologie MeSH
- mlékárenství metody MeSH
- mléko mikrobiologie virologie MeSH
- Ramanova spektroskopie * MeSH
- Streptococcus thermophilus virologie MeSH
- zvířata MeSH
- Check Tag
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
- technické zprávy MeSH
Staphylococcus aureus is a major food-borne pathogen due to the production of enterotoxin and is particularly prevalent in contaminated milk and dairy products. The lactic acid bacteria (LAB) are widely used as biocontrol agents in fermented foods which can inhibit pathogenic flora. In our work, we investigated the influence of three strains of LAB (Lactobacillus plantarum, Streptococcus thermophilus and Enterococcus durans) on the relative expression of three enterotoxin genes (sea, sec, sell) and eight virulence and/or regulatory genes (sarA, saeS, codY, srrA, rot, hld/RNAIII, agrA/RNAII, sigB) in two S. aureus strains (MW2 and Sa1612) in TSB and reduced-fat milk (1.5 %) at 30 °C over a 24-h period. The tested LAB and S. aureus strains proved to be mutually non-competitive or only slightly competitive during co-cultivation. In addition, under the above-mentioned conditions, differential gene expression between the S. aureus MW2 and Sa1612 strains was well documented. S. aureus growth was changed in mixed culture with LAB; however, its effect on the repression of sea and sec expression correlated with production of these virulence factors. In comparison, the presence of LAB strains generally inhibited the expression of sec, sell, sarA, seaS, agrA/RNAII and hld/RNAIII genes. The effect of LAB strains presence on the expression of sea, codY, srrA, rot and sigB genes was medium, time, LAB and S. aureus strain specific. SEA and SEC production was significantly reduced in milk compared to TSB in pure culture. After the 24-h cultivation, S. aureus MW2 and Sa1612 SEC production was 187 and 331 times lower in milk compared to TSB, respectively (0.07 and 0.39 ng/mL in milk, versus 13.1 and 129.2 ng/mL in TSB, respectively). At the same time S. aureus MW2 and Sa1612 SEA production was 77 and 68 times lower in milk compared to TSB, respectively (0.99 and 0.17 ng/mL in milk, versus 76.4 and 11.5 ng/mL in TSB, respectively). This study has revealed new insights into the interaction between S. aureus and LAB (L. plantarum, S. thermophilus, E. durans) on the level of the expression and/or production of S. aureus enterotoxins, regulatory and virulence genes in different media, including milk. This study provides data which may improve the quality of food production.
- MeSH
- Enterococcus fyziologie MeSH
- enterotoxiny biosyntéza genetika MeSH
- faktory virulence genetika MeSH
- kokultivační techniky MeSH
- kultivační média MeSH
- Lactobacillus plantarum fyziologie MeSH
- mikrobiální interakce MeSH
- mléko * MeSH
- potravinářská mikrobiologie MeSH
- regulační geny MeSH
- Staphylococcus aureus genetika růst a vývoj metabolismus patogenita MeSH
- Streptococcus thermophilus fyziologie MeSH
- transkriptom MeSH
- zvířata MeSH
- Check Tag
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
Tato studie se zaobírá posouzením technologických vlastností a probiotického potenciálu původních bakterií St. thermophilus R4 a R14 izolovaných z tradičního alžírského fermentovaného mléka nazývaného “Raib”. Výsledky ukazují, že tyto lokální kmeny produkují kyselinu rychleji, mají dobrou proteolytickou aktivitu, produkují exopolysacharidy a jsou dobrými antagonisty. Výsledky probiotických vlastností ukazují, že tyto kmeny jsou schopné přežít v pH 2.5 a v 0.3 % žlučové kyselině s dobrou adherence na epiteliální buňky. Dále vykazují dobrou viabilitu v simulovaném gastrointestinálním prostředí. Výsledky “cross-streak” testu prokázaly nepřítomnost antagonistické aktivity a potvrdil kompatibilitu mezi těmito kmeny a komerčními Lb. delbrueckii subsp bulgaricus. Testované kmeny vykazují in vitro žádoucí probiotické vlastnosti a jsou vhodnými kandidáty pro jejich použití jako probiotika v potravinářském průmyslu. Keywords: probiotika, Streptococcus thermophilus, tradiční potraviny
This study aimed to assessing the technological traits and probiotic potential of autochthonous St. thermophilus R4 and R14 isolated from Algerian traditional fermented milk cold “Raib”. The results showed that these local strains were fastest acid producing, have good proteolytic activity, have the ability to produce exopolysaccharides and exhibited good antagonistic activity. The results of the probiotic properties showed that these strains were able to survive at pH 2.5 and 0.3 % bile with a good adherence to epithelial cells. These strains showed a good viable count in simulated gastrointestinal juice. The results of cross-streak test showed the absence of antagonistic activity and confirmed the compatibility between these strains and a commercial Lb. delbrueckii subsp bulgaricus. The tested strains were found in vitro possess desirable probiotic properties and they are good candidates for their application as probiotic starter in the food industry. For the Algerian yogurt industry, potential St. thermophilus strains able to be used as starter in combination with other local Lb. delbrueckii subsp bulgaricus may be found.
