Bioactive Hydrogel Formulation Based on Ferulic Acid-Grafted Nano-Chitosan and Bacterial Nanocellulose Enriched with Selenium Nanoparticles from Kombucha Fermentation

Selenium nanoparticles (SeNPs) have specific properties that result from their biosynthesis particularities. Chitosan can prevent pathogenic biofilm development. A wide palette of bacterial nanocellulose (BNC) biological and physical-chemical properties are known. The aim of this study was to develop a hydrogel formulation (SeBNCSFa) based on ferulic acid-grafted chitosan and bacterial nanocellulose (BNC) enriched with SeNPs from Kombucha fermentation (SeNPsK), which could be used as an adjuvant for oral implant integration and other applications. The grafted chitosan and SeBNCSFa were characterized by biochemical and physical-chemical methods. The cell viability and proliferation of HGF-1 gingival fibroblasts were investigated, as well as their in vitro antioxidant activity. The inflammatory response was determined by enzyme-linked immunosorbent assay (ELISA) of the proinflammatory mediators (IL-6, TNF-α, and IL-1β) in cell culture medium. Likewise, the amount of nitric oxide released was measured by the Griess reaction. The antimicrobial activity was also investigated. The grafting degree with ferulic acid was approximately 1.780 ± 0.07% of the total chitosan monomeric units, assuming single-site grafting per monomer. Fourier-transform infrared spectroscopy evidenced a convolution of BNC and grafted chitosan spectra, and X-ray diffraction analysis highlighted an amorphous rearrangement of the diffraction patterns, suggesting multiple interactions. The hydrogel showed a high degree of cytocompatibility, and enhanced antioxidant, anti-inflammatory, and antimicrobial potentials.

Selenium bioactive compounds produced by beneficial microbes

Selenium (Se) is an essential trace element present as selenocysteine (SeCys) in selenoproteins, which have an important role in thyroid metabolism and the redox system in humans. Se deficiency affects between 500 and 1000 million people worldwide. Increasing Se intake can prevent from bacterial and viral infections. Se deficiency has been associated with cancer, Alzheimer, Parkinson, decreased thyroid function, and male infertility. Se intake depends on the food consumed which is directly related to the amount of Se in the soil as well as on its availability. Se is unevenly distributed on the earth's crust, being scarce in some regions and in excess in others. The easiest way to counteract the symptoms of Se deficiency is to enhance the Se status of the human diet. Se salts are the most toxic form of Se, while Se amino acids and Se-nanoparticles (SeNPs) are the least toxic and most bio-available forms. Some bacteria transform Se salts into these Se species. Generally accepted as safe selenized microorganisms can be directly used in the manufacture of selenized fermented and/or probiotic foods. On the other hand, plant growth-promoting bacteria and/or the SeNPs produced by them can be used to promote plant growth and produce crops enriched with Se. In this chapter we discuss bacterial Se metabolism, the effect of Se on human health, the applications of SeNPs and Se-enriched bacteria, as well as their effect on food fortification. Different strategies to counteract Se deficiency by enriching foods using sustainable strategies and their possible implications for improving human health are discussed.

Multi-dimensional experimental and computational exploration of metabolism pinpoints complex probiotic interactions

Multi-strain probiotics are widely regarded as effective products for improving gut microbiota stability and host health, providing advantages over single-strain probiotics. However, in general, it is unclear to what extent different strains would cooperate or compete for resources, and how the establishment of a common biofilm microenvironment could influence their interactions. In this work, we develop an integrative experimental and computational approach to comprehensively assess the metabolic functionality and interactions of probiotics across growth conditions. Our approach combines co-culture assays with genome-scale modelling of metabolism and multivariate data analysis, thus exploiting complementary data- and knowledge-driven systems biology techniques. To show the advantages of the proposed approach, we apply it to the study of the interactions between two widely used probiotic strains of Lactobacillus reuteri and Saccharomyces boulardii, characterising their production potential for compounds that can be beneficial to human health. Our results show that these strains can establish a mixed cooperative-antagonistic interaction best explained by competition for shared resources, with an increased individual exchange but an often decreased net production of amino acids and short-chain fatty acids. Overall, our work provides a strategy that can be used to explore microbial metabolic fingerprints of biotechnological interest, capable of capturing multifaceted equilibria even in simple microbial consortia.

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.

Exploring the new dimensions of selenium research to understand the underlying mechanism of its uptake, translocation, and accumulation

Selenium (Se) is a vital mineral for both plants and animals. It is widely distributed on the earth's crust and is taken up by the plants as selenite or selenate. Plants substantially vary in their physiological response to Se. The amount of Se in edible plants is genetically controlled. Its availability can be determined by measuring its phytoavailability in soil. The low concentration of Se in plants can help them in combating stress, whereas higher concentrations can be detrimental to plant health and in most cases it is toxic. Thus, solving the double-edged sword problem of nutritional Se deficiency and its elevated concentrations in environment requires a better understanding of Se uptake and metabolism in plants. The studies on Se uptake and metabolism can help in genetic biofortification of Se in plants and also assist in phytoremediation. Moreover, Se uptake and transport, especially biochemical pathways of assimilation and incorporation into proteins, offers striking mechanisms of toxicity and tolerance. These developments have led to a revival of Se research in higher plants with significant break throughs being made in the previous years. This review explores the new dimensions of Se research with major emphasis on key research events related to Se undertaken in last few years. Further, we also discussed future possibilities in Se research for crop improvement.

The Russian Doll Model: How Bacteria Shape Successful and Sustainable Inter-Kingdom Relationships

Successful inter-kingdom relationships are based upon a dynamic balance between defense and cooperation. A certain degree of competition is necessary to guarantee life spread and development. On the other hand, cooperation is a powerful tool to ensure a long lasting adaptation to changing environmental conditions and to support evolution to a higher level of complexity. Bacteria can interact with their (true or potential) parasites (i.e., phages) and with their multicellular hosts. In these model interactions, bacteria learnt how to cope with their inner and outer host, transforming dangerous signals into opportunities and modulating responses in order to achieve an agreement that is beneficial for the overall participants, thus giving rise to a more complex "organism" or ecosystem. In this review, particular attention will be addressed to underline the minimal energy expenditure required for these successful interactions [e.g., moonlighting proteins, post-translational modifications (PTMs), and multitasking signals] and the systemic vision of these processes and ways of life in which the system proves to be more than the sum of the single components. Using an inside-out perspective, I will examine the possibility of multilevel interactions, in which viruses help bacteria to cope with the animal host and bacteria support the human immune system to counteract viral infection in a circular vision. In this sophisticated network, bacteria represent the precious link that insures system stability with relative low energy expenditure.

Biotransformation of Selenium by Lactic Acid Bacteria: Formation of Seleno-Nanoparticles and Seleno-Amino Acids

Selenium (Se) is an essential micronutrient for the majority of living organisms, and it has been identified as selenocysteine in the active site of several selenoproteins such as glutathione peroxidase, thioredoxin reductase, and deiodinases. Se deficiency in humans is associated with viral infections, thyroid dysfunction, different types of cancer, and aging. In several European countries as well as in Argentina, Se intake is below the recommended dietary Intake (RDI). Some lactic acid bacteria (LAB) can accumulate and bio-transform selenite (toxic) into Se-nanoparticles (SeNPs) and Se-amino acids (non-toxic). The microbial growth, Se metabolite distribution, and the glutathione reductase (involved in selenite reduction) activity of Se-enriched LAB were studied in this work. The ninety-six assayed strains, belonging to the genera Lactococcus, Weissella, Leuconostoc, Lactobacillus, Enterococcus, and Fructobacillus could grow in the presence of 5 ppm sodium selenite. From the total, eight strains could remove more than 80% of the added Se from the culture medium. These bacteria accumulated intracellularly between 1.2 and 2.5 ppm of the added Se, from which F. tropaeoli CRL 2034 contained the highest intracellular amount. These strains produced only the seleno-amino acid SeCys as observed by LC-ICP-MS and confirmed by LC-ESI-MS/MS. The intracellular SeCys concentrations were between 0.015 and 0.880 ppm; Lb. brevis CRL 2051 (0.873 ppm), Lb. plantarum CRL 2030 (0.867 ppm), and F. tropaeoli CRL 2034 (0.625 ppm) were the strains that showed the highest concentrations. Glutathione reductase activity values were higher when the strains were grown in the presence of Se except for the F. tropaeoli CRL 2034 strain, which showed an opposite behavior. The cellular morphology of the strains was not affected by the presence of Se in the culture medium; interestingly, all the strains were able to form spherical SeNPs as determined by transmission electron microscopy (TEM). Only two Enterococcus strains produced the volatile Se compounds dimethyl-diselenide identified by GC-MS. Our results show that Lb. brevis CRL 2051, Lb. plantarum CRL 2030, and F. tropaeoli CRL 2034 could be used for the development of nutraceuticals or as starter cultures for the bio-enrichment of fermented fruit beverages with SeCys and SeNPs.

Cellulomonas fimi secretomes: In vivo and in silico approaches for the lignocellulose bioconversion

Lignocellulose degradation is a challenging step for value added products and biofuels production. Cellulomonas fimi secretes complex mixtures of carbohydrate active enzymes (CAZymes) which synergistically degrade cellulose and hemicelluloses. Their characterization may provide new insights for enzymatic cocktails implementation. Bioinformatic analysis highlighted 1127 secreted proteins, constituting the in silico secretome, graphically represented in a 2DE map. According to Blast2GO functional annotation, many of these are involved in carbohydrates metabolism. In vivo secretomes were obtained, growing C. fimi on glucose, CMC or wheat straw for 24 h. Zymography revealed degradative activity on carbohydrates and proteomic analysis identified some CAZymes, only in secretomes obtained with CMC and wheat straw. An interaction between cellobiohydrolases is proposed as a strategy adopted by soluble multimodular cellulases. Such approach can be crucial for a better characterization and industrial exploitation of the synergism among C. fimi enzymes.

Bioactive Molecules Released in Food by Lactic Acid Bacteria: Encrypted Peptides and Biogenic Amines

Lactic acid bacteria (LAB) can produce a huge amount of bioactive compounds. Since their elective habitat is food, especially dairy but also vegetal food, it is frequent to find bioactive molecules in fermented products. Sometimes these compounds can have adverse effects on human health such as biogenic amines (tyramine and histamine), causing allergies, hypertensive crises, and headache. However, some LAB products also display benefits for the consumers. In the present review article, the main nitrogen compounds produced by LAB are considered. Besides biogenic amines derived from the amino acids tyrosine, histidine, phenylalanine, lysine, ornithine, and glutamate by decarboxylation, interesting peptides can be decrypted by the proteolytic activity of LAB. LAB proteolytic system is very efficient in releasing encrypted molecules from several proteins present in different food matrices. Alpha and beta-caseins, albumin and globulin from milk and dairy products, rubisco from spinach, beta-conglycinin from soy and gluten from cereals constitute a good source of important bioactive compounds. These encrypted peptides are able to control nutrition (mineral absorption and oxidative stress protection), metabolism (blood glucose and cholesterol lowering) cardiovascular function (antithrombotic and hypotensive action), infection (microbial inhibition and immunomodulation) and gut-brain axis (opioids and anti-opioids controlling mood and food intake). Very recent results underline the role of food-encrypted peptides in protein folding (chaperone-like molecules) as well as in cell cycle and apoptosis control, suggesting new and positive aspects of fermented food, still unexplored. In this context, the detailed (transcriptomic, proteomic, and metabolomic) characterization of LAB of food interest (as starters, biocontrol agents, nutraceuticals, and probiotics) can supply a solid evidence-based science to support beneficial effects and it is a promising approach as well to obtain functional food. The detailed knowledge of the modulation of human physiology, exploiting the health-promoting properties of fermented food, is an open field of investigation that will constitute the next challenge.

Ten years of subproteome investigations in lactic acid bacteria: A key for food starter and probiotic typing

The definition of safety and efficacy of food-employed bacteria as well as probiotic strains is a continuous, often unattended, challenge. Proteomic techniques such as 2DE, DIGE and LC/LC-MS/MS are suitable and powerful tools to reveal new aspects (positive and negative) of "known" and "unknown" strains that can be employed in food making and as nutraceutical supplements for human health. Unfortunately, these techniques are not used as extensively as it should be wise. The present report describes the most significant results obtained by our research group in 10years of study on subproteomes in bacteria, chiefly lactic acid bacteria. Production of desired and undesired metabolites, differences between strains belonging to same species but isolated from different ecological niches, the effect of cryoprotectants on survival to lyophilization as well as the adhesive capability of strains, were elucidated by analysis of cytosolic, membrane-enriched, surface and extracellular proteomes. The present review opens a window on a yet largely underexplored field and highlights the huge potential of subproteome investigations for more rational choice of microbial strains as food starters, probiotics and for production of nutraceuticals. These analyses will hopefully contribute to manufacturing safer and healthier food and food supplements in the near future. This article is part of a Special Issue entitled: HUPO 2014.