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.

Growth and exopolysaccharide production by Lactobacillus helveticus ATCC 15807 in an adenine-supplemented chemically defined medium.

AIMS: To analyse the exopolysaccharide (EPS) production by Lactobacillus helveticus ATCC 15807 in a chemically defined medium (CDM) and the effect of nutrients and stress culture conditions on cell growth and EPS formation. METHODS AND RESULTS: Cultures were conducted in CDM: (i) containing essential and nonessential bases and vitamins; (ii) without nonessential bases and vitamins [Simplified CDM (SCDM)]; (iii) SCDM supplemented individually with vitamins and bases. The influence of carbohydrates, pH and osmotic culture conditions on growth and polymer formation was analysed. Adenine and lactose stimulated both growth and EPS production. Constant pH fermentations (4.5 and 6.2) did not improve EPS synthesis while NaCl and glycerol were detrimental for growth and polymer formation. In all media the EPS monomer composition was glucose and galactose (2.5 : 1). CONCLUSIONS: A SCDM containing adenine and lactose was optimal for cell growth and EPS formation by Lact. helveticus ATCC 15807. Controlled pH (6.2 and 4.5) and osmotic stress culture conditions did not improve polymer production. The EPS characteristics were identical in all media. SIGNIFICANCE AND IMPACT OF THE STUDY: This work provides a better knowledge on EPS synthesis by Lact. helveticus. A CDM to perform regulation studies on EPS production by Lact. helveticus species is now available.

Sensitivity and predictive value of serum ferritin and free erythrocyte protoporphyrin for iron deficiency.

The sensitivity and predictive value of serum ferritin (SF) and free erythrocyte protoporphyrin (FEP) for iron deficiency (ID) was evaluated by studying 272 subjects with uncomplicated ID (174 with anemia and 98 without) in whom diagnosis was confirmed by the response to iron supplementation. Overall, the sensitivity, at 95% specificity, was 82% (79% in women, 94% in men) for SF and 61% (60% in women, 65% in men) for FEP. The sensitivity varied as a function of hemoglobin values, dropping from over 90% for both tests in the case of severe anemia, to approximately 70% for SF and less than 50% for FEP in the absence of anemia. The predictive value decreases more sharply for FEP than for SF with increasing hemoglobin levels. It is concluded that SF is preferable to FEP for the detection of ID, particularly in the absence of anemia. However, owing to the unsatisfactory predictive value at low prevalence, SF should be used as a screening test for ID without anemia only when the prevalence is at least 20%.