Distribution characteristics of organic selenium in Se-enriched Lactobacillus (Lactobacillus paracasei)

From soil to the intestinal tract: The key role of beneficial elements and probiotics in promoting health and longevity

Although soil quality and gut probiotics have been extensively accepted as critical for human health, the combined effects of soil and fecal bacteria on public health remain underexplored. This study collected soil and human fecal samples from three towns with high, medium, and low proportion of longevous populations in a well-known longevity region in Yangtze River Delta, China. Beneficial elements were detected in all soils, including selenium (0.01-0.05 mg kg-1), germanium (1.07-1.44 mg kg-1), boron (0.42-1.49 mg kg-1), zinc (1.07-1.70 mg kg-1) and manganese (38.78-43.52 mg kg-1). These elements were more abundant in high-proportion region (HP) compared to medium (MP) and low (LP) proportion region (p < 0.05). Similar dominant bacteria were detected in all soils and feces, including Proteobacteria (29.93 %), Acidobacteriota (16.23 %), and Bacillus (2.25 %). Notably, positive correlations were detected between beneficial metal contents and soil bacterial abundance (p < 0.05), suggesting a role in promoting bacterial growth. Moreover, beneficial element metabolic genes, such as zupT (encoding high-affinity zinc transporter for active zinc ion transport) and mntA (encoding manganese ion transporter protein) were significantly enriched in HP soil and fecal bacteria (p < 0.05). Additionally, Source Tracker analysis indicated that 41.13 % of fecal bacteria in HP area originated from HP soil bacteria. Structural equation model indicated that soil beneficial elements significantly enhanced the relative abundance of probiotic associated genes in the dominant fecal bacteria (path coefficients of 0.869 and 0.905, respectively; p < 0.05). Together, soil-borne beneficial elements promote intestinal bacterial functionality, contributing to human health and longevity.

Revealing the impact of organic selenium-enriched Lactiplantibacillus plantarum NML21 on yogurt quality through volatile flavor compounds and untargeted metabolomics

Effective selenium supplementation strategies are essential for alleviating global selenium deficiency. This study utilized the high‑selenium-tolerant strain Lactiplantibacillus plantarum NML21 to produce selenium-enriched yogurt, successfully converting inorganic Se(IV) into organic selenium, with selenoproteins accounting for 69.52 % of the total selenium content (995.19 ± 68.60 μg/g). Selenium-enriched yogurt exhibited excellent physicochemical properties and antioxidant activity. Volatile flavor analysis identified 36 compounds, with NML21 and SeNML21 significantly enhancing ketone flavors in yogurt, particularly increasing the contents of 2-heptanone and 2,3-pentanedione. Untargeted metabolomics identified 215 non-volatile metabolites, with NML21 and SeNML21 significantly regulating key metabolic pathways, including the phosphotransferase system, ABC transporters, and amino acid biosynthesis, promoting the accumulation of beneficial metabolites. Selenium specifically influenced the biosynthesis pathways of ABC transporters, phenylalanine, tyrosine, and tryptophan. This study demonstrates that NML21 is a promising strain for producing selenium-enriched functional yogurt, offering innovative perspectives for dietary selenium supplementation and functional food development.

Selenium-enriched Lactiplantibacillus plantarum alleviates alkalinity stress-induced selective hepatic insulin resistance in common carp

Carbonate alkalinity is one of the primary factors limiting saline-alkaline water aquaculture, and high alkalinity can lead to respiratory alkalosis, which is hazardous to fish health. Selenium (Se) and Lactiplantibacillus plantarum (L. plantarum) can be used for the biosynthesis of organic selenium (selenium-enriched Lactiplantibacillus plantarum: SL), which has low toxicity, high bioavailability, and the promotion of metabolism. Additionally, it can be used as a feed additive in aquaculture. In the present study, we established a model of chronic alkalinity stress in common carp and added SL to the feed. We found that alkalinity stress can cause severe hepatic dysfunction in common carp, as well as disrupt the intestinal barrier, further contributing to the translocation of enterogenous lipopolysaccharides through portal circulation and exacerbating liver injury. SL alleviated glucose-lipid metabolism abnormalities of the liver while reducing serum LPS levels and reduction of enterogenous LPS translocation to the liver, thus significantly reducing the degree of intestinal villi damage, hepatocyte vacuolisation, and nuclear damage. The significantly increased activities of SOD, GSH-Px, CAT, and T-AOC revealed that SL improved the antioxidant capacity of common carp. SL inhibited the alkalinity stress-induced overexpression of genes related to lipid synthesis and gluconeogenesis by modulating the P13K/Akt/FoxO1 signalling pathway, thus alleviating selective hepatic insulin resistance. SL attenuated the inflammatory response by modulating the mRNA expression levels of IL-7, IL-6, TNF-α and IL-10. In addition, apparent increase in the abundance of pathogenic bacteria (Brevinema, Bosea, Luteolibacter, and Vibrio) and apparent reduction in the abundance of beneficial bacteria (Cetobacterium, ZOR0006, and Shewanella) were closely related to the hepato-intestinal circulation process in carp exposed to alkalinity stress. SL regulated the hepato-intestinal circulation, reduced the abundance of Brevinema, Bosea, Luteolibacter, and Vibrio, increased the abundance of Cetobacterium, ZOR0006, and Shewanella, alleviated alkalinity stress-induced damage to intestinal microvilli (villus height and width), and significantly restored normal liver and intestinal functions. This study reveals the physiological regulatory mechanism by which Se-enriched L. plantarum through liver-intestinal axis alleviates alkalinity stress-induced hepatic insulin resistance and may provide new ideas and a theoretical basis for protecting against alkalosis and treating insulin resistance.

Growth and selenium bioaccumulation in rape seedlings promoted by strain Limosilactobacillus sp. LF-17

Selenium (Se) is an essential trace element that plays a critical role in human tissue formation, metabolism, and physiological functions. However, many individuals worldwide suffer from Se deficiency diseases. This study aims to evaluate the impact of Se-tolerant LF-17 agents and exogenous Na2SeO3 application on the growth, enzyme activity, and metabolic characteristics of rape seedlings. Treatment LF-3 (inoculation of Se-tolerant LF-17 agent and exogenous Na2SeO3, with the soil Se concentration of 5 mg/kg) led to a 38.62% increase in plant height and a 116.7% increase in fresh weight. And the Se-tolerant LF-17 agent in treatment LF-3 also reduced the oxidative stress induced by exogenous Na2SeO3 compared to that of treatment LF-2 (with the same amount exogenous Na2SeO3 only), as evidenced by the lower activities of SOD, POD, and CAT, as well as less content of malondialdehyde. Furthermore, the upregulation of metabolic pathways such as "cuticle, suberine, and wax biosynthesis" "flavonoid biosynthesis," and "terpenoid backbone biosynthesis" enhanced the plant's stress resistance as revealed by non-targeted metabolomics sequencing method. This approach offers promising applications for improving Se bioavailability in crops, mitigating Se toxicity, addressing global Se deficiency challenges and is expected to contribute to fulfilling the Se supplementation needs of the population.

Selenium enrichment enhances the alleviating effect of Lactobacillus rhamnosus GG on alcoholic liver injury in mice

Selenium-enriched probiotics have attracted much attention due to the physiological activities of both probiotics and selenium (organic selenium). In this study, we investigated the mitigating effect of selenium-enriched Lactobacillus rhamnosus GG (LGG@Se) and its pathway on alcohol-induced liver injury (ALI) in mice. The results showed that LGG@Se was superior to LGG and sodium selenite in alleviating ALI. Oral LGG@Se effectively prevented lipid metabolism disorders and liver oxidative damage in mice caused by excessive alcohol intake. 16S amplicon sequencing showed that LGG@Se intervention increased the abundance of beneficial bacteria and suppressed the growth of harmful bacteria in the intestinal tract of over-drinking mice, and thus effectively modulated the homeostasis of intestinal flora, which were highly correlated with the improvement of liver function. Liver metabolomics analysis indicated that LGG@Se intervention altered liver metabolic profiling, and the characteristic biomarkers were mainly involved in amino acid metabolism, including alanine, aspartate and glutamate metabolism, arginine biosynthesis, etc. In addition, LGG@Se intervention modulated the expression of genes and proteins related to lipid metabolism and oxidative stress in liver of over-drinking mice. Western blot analysis revealed that LGG@Se intervention up-regulated the expression of intestinal barrier function-related proteins, thereby ameliorating alcohol-induced intestinal barrier damage. Collectively, these findings provide scientific evidence that LGG@Se possesses the biological activity of improving alcohol-induced lipid metabolism and intestinal microbiota disorder.

Characterization and subcellular localization of selenium in Limosilactobacillus fermentum Ln-9 obtained by intense pulsed light-ultraviolet combined mutagenesis

Lactic acid bacteria (LAB) can convert inorganic selenium (Se) to organic Se and elemental forms with low toxicity and high bioavailability, but a comprehensive Se analysis of Se-enriched LAB is lacking. In this study, Limosilactobacillus fermentum Ln-9 was obtained by intense pulsed light-ultraviolet combined mutagenesis, and its characteristics and subcellular localization of Se were analyzed. The results displayed that Ln-9 accumulated 3.03 times Se that of the original strain. Under optimal fermentation conditions, the total Se content of Se-enriched Ln-9 (SeLn-9) reached 12.16 mg/g with 96.34% contained in Se nanoparticles (SeNPs), which was much higher than that of organic macromolecules. Furthermore, SeNPs were mainly localized outside the cell, Se-proteins were in the membrane and cytoplasmic fractions, and Se-polysaccharides were in the membrane fraction. Besides, SeLn-9 maintained a good morphology and gastrointestinal tolerance and had an enhanced antioxidant capacity. These findings make Ln-9 promising for applications in the food industry.

Bioreduction of Se(IV) by Lactiplantibacillus plantarum NML21 and synthesis of selenium nanospheres Se(0)

Selenium nanospheres (SeNPs) show less toxicity and greater bioavailability than selenite salts. This research demonstrated the substantial tolerance and efficient conversion of Se(IV) into SeNPs by Lactiplantibacillus plantarum NML21. The bioreduction process of Se(IV) and the properties of SeNPs, including their morphology, particle size, and stability, were investigated with techniques including SEM, EDX, TEM, XPS, FT-IR, dynamic light scattering, XRD, and Raman spectroscopy. Under high selenium stress, certain cells displayed significant deformation and rupture, and released SeNPs as the main product of the bioreduction of Se(IV). These SeNPs were red, amorphous, zero-valent, and spherical, with an average diameter of 160 nm. Spectroscopic analysis highlighted that the functional groups of CO and CO are key to the bioreduction of Se(IV). The study suggested preliminary mechanisms for the bioreduction of Se(IV) and the formation and release of SeNPs by lactic acid bacteria. NML21 may therefore be a promising candidate for SeNPs synthesis.

Selenized non-Saccharomyces yeasts and their potential use in fish feed

Selenium (Se) is a vital trace element, essential for growth and other biological functions in fish. Its significance lies in its role as a fundamental component of selenoproteins, which are crucial for optimal functioning of the organism. The inclusion of Se in the diets of farmed animals, including fish, has proved invaluable in mitigating the challenges arising from elemental deficiencies experienced in captivity conditions due to limitations in the content of fishmeal. Supplementing diets with Se enhances physiological responses, particularly mitigates the effects of the continuous presence of environmental stress factors. Organic Se has been shown to have higher absorption rates and a greater impact on bioavailability and overall health than inorganic forms. A characteristic feature of yeasts is their rapid proliferation and growth, marked by efficient mineral assimilation. Most of the selenized yeasts currently available in the market, and used predominantly in animal production and aquaculture, are based on Saccharomyces cerevisiae, which contains selenomethionine (Se-Met). The object of this review is to highlight the importance of selenized yeasts. In addition, it presents metabolic and productive aspects of other yeast genera that are important potential sources of organic selenium. Some yeast strains discussed produce metabolites of interest such as lipids, pigments, and amino acids, which could have applications in aquaculture and further enrich their usefulness.

Screening and Identification of Soil Selenium-Enriched Strains and Application in Auricularia auricula

Selenium (Se) is an essential trace element for human physiological metabolism. The application of organic Se as a source to cultivate Se-rich plants for micronutrient supplementation has been receiving increasing attention. In our study, a bacterial strain named H1 was isolated from the soil in Heilongjiang Province, China, and under optimal culture conditions, the unit Se content could reach 3000 μg·g-1 and its 16S ribosomal DNA sequence seemed to be a new molecular record of an Enterobacter species. After the domestication of Se tolerance and Se-rich experiments, H1 can be used as a Se source for cultivation of Se-rich Auricularia auricula. The results showed that soluble protein, soluble sugar, free amino acid and vitamin C contents in Auricularia auricula were notably increased by 28.7%, 21.8%, 32.5% and 39.2% under the treatment of Se concentration of 0.24 mg·kg-1, respectively. These findings enhance our understanding that H1 is more conducive to Se uptake and nutrient accumulation.

Comprehensive distribution and species of selenium in Se-enriched Pichia kudriavzevii 1845

This study is the first to demonstrate the yeast Pichia kudriavzevii can effectively deliver Se and investigate the distribution and species of Se in Se-enriched P. kudriavzevii. Results showed that P. kudriavzevii can accumulate Se and convert 84.883% of absorbed Se into organic forms, of which 78.338% was incorporated into protein, 1.978% combined with polysaccharides, and 0.456% bound to nucleic acid. Besides, water-soluble, salt-soluble, and alkali-soluble proteins account for 49.398%, 1.867%, and 20.628% of selenoprotein, respectively. The dominant Se species were SeCys2 and MeSeCys. Additionally, Se-enrichment enhanced nutritional value of P. kudriavzevii by increasing the levels of amino acids, iron, and zinc. The activity of key rate-limiting enzyme sephosphate synthetase involved in Se biotransformation was improved after Se enrichment. The extracellular pH results suggest that Se enrichment ability can be further enhanced by elevating pH. These results suggest P. kudriavzevii holds great promise as an effective vehicle for delivering Se.

Advances in the Study of Selenium-Enriched Probiotics: From the Inorganic Se into Se Nanoparticles

Selenium (Se) is a momentous metallic element that plays an irreplaceable role in biochemical activities. Se deficiency remains a nutritional challenge across the world. Organic Se supplementation is the most effective treatment means for Se deficiency. Organic Se transformed from Se-enriched probiotics show outstanding excellent properties in antibacteria, anti-oxidation, anti-inflammation, and immunoregulation. Studying the influencing factors for Se enrichment capacity and enrichment mechanisms of Se-enriched probiotics is conducive to the exploit of more potent Se-enriched probiotics. Se-enriched probiotics transform inorganic Se into Se nanoparticles (SeNPs), which have been widely used in animal husbandry and biomedical field. In this paper, the novel development of Se-enriched probiotics is reviewed, and the bioactivities of SeNPs are assessed, so as to display their potential application prospects. The excellent role of SeNPs in anti-oxidation is summarized, and the mechanism by which SeNPs improve Se deficiency and boost animal health is explained.

Biosynthesis of selenium nanoparticles by lactic acid bacteria and areas of their possible applications

Lactic acid bacteria, being generally recognized as safe, are the preferred choice among other microbial producers of selenium nanoparticles. For successful production of SeNPs, it is necessary to take into account the physiological properties of the bacterium used as a biotransformer of inorganic forms of selenium in Se⁰. The antimicrobial and antioxidant activity of SeNPs allows to use them in the form of pure nanoparticles or biomass of lactic acid bacteria enriched with selenium in preparation of food, in agriculture, aquaculture, medicine, veterinary, and manufacturing of packing materials for food products. To attract attention to the promising new directions of lactic acid bacteria applications and to accelerate their implementation, the examples of the use of SeNPs synthesized by lactic acid bacteria in the mentioned above areas of human activity are described.

Enrichment and Distribution of Selenium in Pediococcus acidilactici MRS-7: Impact on Its Biochemical Composition, Microstructure, and Gastrointestinal Survival

Lactic acid bacteria can convert selenium (Se) from inorganic to organic and elemental forms, but the distribution and existence form of organic Se in the bacteria are not clear after Se enrichment, and the effects of selenization on the growth and nutritional value of strains also need to be studied. In this study, Pediococcus acidilactici MRS-7 could absorb up to 67% of inorganic Se and convert most of it into organic Se; about 75% of organic Se was selenoprotein, 2.7% was Se-polysaccharide, and 4.6% was Se-nucleic acid. Additionally, Se-enriched treatment increased the levels of amino acids and essential elements in P. acidilactici MRS-7. Finally, after Se enrichment, Se nanoparticles (SeNPs) were found on the surface of P. acidilactici MRS-7, but they had no harmful effect on its morphology, and its survival during gastrointestinal digestion was not affected, indicating that SeP has potential probiotic value in the food industry.