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.

Soymilk fermentation by Enterococcus faecalis VB43 leads to reduction in the immunoreactivity of allergenic proteins ß-conglycinin (7S) and glycinin (11S).

Food allergies represent a serious problem affecting human health and soy proteins rank among the most allergenic proteins from food origin. The proteolytic enzymes produced by lactic acid bacteria (LAB) can hydrolyse the major allergens present in soybean, reducing their immunoreactivity. Many studies have reported the ability of LAB to ferment soy-based products; while the majority of them focus on the improvement of the sensory characteristics and functionality of soy proteins, a lack of information about the role of lactic fermentation in the reduction of immunoreactivity of these proteins exists. The aim of the present study was to evaluate the capability of the proteolytic strain Enterococcus faecalis VB43 to hydrolyse the main allergenic proteins present in soymilk and to determine the immunoreactivity of the obtained hydrolysates. Sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) results of fermented soymilk demonstrated complete hydrolysis of the ß-subunit from ß-conglycinin and the acidic polypeptide from glycinin. Reversed phase high performance liquid chromatography (RP-HPLC) analysis of the peptides released after hydrolysis revealed the appearance of new peptides and the disappearance of non-hydrolysed proteins, indicating extensive hydrolysis of the substrate. Results from competitive enzyme-linked immunosorbent assay (ELISA) tests clearly indicated a reduction in the immunoreactivity (more than one logarithmic unit) in the fermented sample as compared to the non-fermented control. Our results suggest that the soymilk fermented by E. faecalis VB43 may induce lower allergic responses in sensitive individuals. The strain E. faecalis VB43 may be considered as an excellent candidate to efficiently reduce the immunoreactivity of soymilk proteins.

Prevention of chronic gastritis by fermented milks made with exopolysaccharide-producing Streptococcus thermophilus strains.

Acetyl-salicylic acid (ASA) is a nonsteroidal antiinflammatory/analgesic drug, which may cause gastritis or stomach ulcers if intensively employed. Exopolysaccharide (EPS)-producing lactic acid bacteria have been claimed to induce immunostimulatory/antiulcer effects in the host. This study investigated the potential preventive effect of fermented milks (FM) with EPS-producing Streptococcus thermophilus strains (CRL 1190 and CRL 804) on an in vivo model of chronic gastritis. Fermented milks (2 EPS(+) and 1 EPS(-), separately) were fed to BALB/c mice for 7 d before inducing gastritis with ASA (400 mg/kg of body weight per day for 10 d; gastritis group, n = 5). Appropriate control groups (ASA administered but not given FM, n = 5; and ASA not administered but given FM) were included in this study. Gastric inflammatory activity was evaluated through the stomach's histology and the number of IFNgamma(+) and IL-10(+) cytokine-producing cells in the gastric mucosa. Only mice preventively treated with the EPS-producing Strep. thermophilus CRL 1190 FM and later administered ASA did not develop gastritis, showing a conserved gastric mucosa structure similar to those of healthy mice. A marked decrease of IFNgamma(+)- and increase of IL-10(+)-producing cells compared with the gastritis group mice were observed. Purified EPS from Strep. thermophilus CRL 1190 resuspended in autoclaved milk was also effective for gastritis prevention. The EPS-protein interaction might be responsible for the observed gastroprotective effect; such interactions may be affected by industrial manufacturing conditions. The results indicate that the FM with Strep. thermophilus CRL 1190 or its EPS could be used in novel functional foods for preventing chronic gastritis.

Functionality of exopolysaccharides produced by lactic acid bacteria in an in vitro gastric system.

AIMS: To evaluate whether slime-exopolysaccharides (EPS) or capsular-polysaccharide (CPS) production could protect the polymer-producing strains Streptococcus thermophilus CRL 1190 and Lactobacillus casei CRL 87 against the harsh conditions of an in vitro gastric system (GS). EPS stability on the GS was studied. METHODS AND RESULTS: An in vitro GS model containing human saliva and gastric juice was standardized. Polymer functionality on the cell viability and metabolic activity of the EPS-producing strains in the GS acidic conditions was evaluated. Two isogenic EPS/CPS deficient mutants were used for comparison. EPS or CPS conferred no significant protection on the cell viability of the studied strains after passage through the GS conditions. However, the phospho- and beta-galactosidase activities of the EPS(+) strains were higher than those of the EPS(-). Cytoplasmic alterations in the wild-type and mutant strains and partial degradation of both EPS were detected. CONCLUSIONS: The presence of EPS/CPS protected the metabolic activity of the assayed LAB strains, but had no effect on survival at low pH. SIGNIFICANCE AND IMPACT OF THE STUDY: The presence of EPS/CPS as well as polymer resistance to the harsh conditions of the human GS could impact positively in probiotic strains to exert their properties in the host.

Sensitivity of capsular-producing Streptococcus thermophilus strains to bacteriophage adsorption.

AIMS: To determine whether the presence and type of exopolysaccharides (EPS), slime-EPS or capsular, and the structural characteristics of the polymers produced by Streptococcus thermophilus strains could interfere with or be involved in phage adsorption. METHODS AND RESULTS: Phage-host interactions between eight EPS-producing Strep. thermophilus strains (CRL419, 638, 804, 810, 815, 817, 821, 1190) and five streptococcus specific phages (phiYsca, phi3, phi5, phi6, phi8) isolated from Argentinean faulty fermentation failed yoghurts were evaluated. No relationship was found between the EPS chemical composition and the phage sensitivity/resistance phenotype. In general, the capsular-producing strains were more sensitive to phage attacks than the noncapsular-producing strains. Streptococcus thermophilus CRL1190 (capsular-producing) was the only strain sensitive to all bacteriophages and showed the highest efficiency of plating. Phage adsorption to a capsular-negative, EPS low-producing mutant of strain CRL1190 was reduced, especially for phiYcsa and phi8. CONCLUSIONS: The presence of capsular polysaccharide surrounding the cells of Strep. thermophilus strains could play a role in the adsorption of specific phages to the cells. SIGNIFICANCE AND IMPACT OF THE STUDY: Capsular-producing Strep. thermophilus strains should be evaluated for their bacteriophage sensitivity if they are included in starter cultures for the fermented food industry.

Hydrolysis of whey proteins by Lactobacillus acidophilus, Streptococcus thermophilus and Lactobacillus delbrueckii ssp. bulgaricus grown in a chemically defined medium.

AIMS: To evaluate the ability of themophilic lactic acid bacteria (LAB) to hydrolyse the whey proteins beta-lactoglobulin (BLG) and alpha-lactalbumin (ALA) in a chemically defined medium (CDM). METHODS AND RESULTS: The ability of three LAB strains to hydrolyse BLG and ALA was studied in a CDM supplemented with these proteins or whey protein concentrate (WPC). Protein hydrolysis was determined by Tricine/SDS-PAGE and RP-HPLC. Maximum BLG (21%) and ALA (26%) degradation by LAB was observed using WPC. Under starving conditions, BLG degradation was greater for Lactobacillus delbrueckii ssp. bulgaricus CRL 454 than for Lactobacillus acidophilus CRL 636 and Streptococcus thermophilus CRL 804. All three strains showed different peptide profiles and were not able to hydrolyse ALA under starvation. CONCLUSIONS: The assayed LAB strains were able to degrade BLG during growth in a CDM and under starving conditions. The different peptide profiles obtained indicate distinct protease specificities. SIGNIFICANCE AND IMPACT OF THE STUDY: These strains could be used as adjunct cultures to increase BLG digestibility in whey-based or whey-containing foods. To our knowledge, this is the first report on the ability of a Lact. acidophilus strain to degrade BLG.

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.

Risk of transmission of hepatitis B virus from anti-HBC positive cadaveric organ donors: a collaborative study.

Organ donors with a serologic profile of recovered (HBsAg negative and/or anti-HBc IgG positive) hepatitis B virus infection (HBV) have been reported to transmit HBV to recipients. In Italy, up until 2002, anti-HBc determination was not mandatory. We retrospectively evaluated the incidence of HBV transmission among recipients transplanted with organs from anti-HBc positive donors from 1997 to 1999. Anti-HBc was screened in 886 available sera among 964 HBsAg and anti-HCV negative donors. HBV transmission was evaluated in 325 kidney, liver, and heart recipients according to their pretransplant HBV serum profile. Of 210 anti-HBc positive donors, 185 were anti-HBc positive/anti-HBs positive and 25 anti-HBc positive/anti-HBs negative with a prevalence of 20.8% and 2.8%, respectively. One hundred seven sera (51%) were collected from donors after transfusion of blood components, the remainder were either before transfusion or from nontransfused donors. The 210 anti-HBc positive subjects donated 356 kidneys, 117 livers and 117 hearts, among whom follow-up is presently available for 251 kidney, 61 liver, and 25 heart recipients. No HBV transmission was observed independent of the recipient immunological profile among the kidney or heart recipients. In liver recipients, no transmission was reported in recovered or vaccinated patients, while a high incidence (43%) of de novo hepatitis was observed among naive patients. In conclusion, there does not seem to be a risk of transmitting HBV through anti-HBc positive transplants in heart and kidney recipients; only naive liver recipients are at high risk of HBV infection.

Exopolysaccharide biosynthesis by Lactobacillus helveticus ATCC 15807.

Exopolysaccharide (EPS) production and the activities of the enzymes involved in sugar nucleotide biosynthesis in Lactobacillus helveticus ATCC 15807 under controlled pH conditions were investigated. Batch fermentations using lactose as energy source showed higher EPS synthesis by L. helveticus ATCC 15807 at pH 4.5 with respect to pH 6.2, the enzyme alpha-phosphoglucomutase (alpha-PGM) being correlated with both total and specific EPS production. When glucose was used as carbon source instead of lactose, the lower EPS synthesis obtained was linked to a decrease in alpha-PGM and galactose 1-phosphate-uridyltransferase (GalT) activities, the reduction of the latter being more pronounced. Higher EPS production by L. helveticus ATCC 15807 at the acidic constant pH of 4.5 requires that both alpha-PGM and GalT activities are high. These enzymes are needed to synthesize UDP-glucose and UDP-galactose for supplying the corresponding monomers for EPS biosynthesis. Although differences are observed in EPS production by this strain regarding the energy source (lactose or glucose), the monomeric composition of the polymers produced is independent of the carbohydrate used. The obtained results contribute to a better understanding of the physiological factors that affect EPS biosynthesis by lactobacilli, which could help in the correct handling of the fermentation parameters within the fermented dairy industry.

UDP-galactose 4-epimerase: a key enzyme in exopolysaccharide formation by Lactobacillus casei CRL 87 in controlled pH batch cultures.

AIMS: To evaluate the relationship between exopolysaccharide (EPS) production and the sugar nucleotide biosynthetic enzymes in Lactobacillus casei CRL 87 under optimum growth conditions for polymer formation: controlled pH on galactose or glucose. Studies with an EPS mutant were carried out to determine the key enzymes in EPS synthesis under the above culture conditions. METHODS AND RESULTS: EPS concentration was estimated by the phenol/sulphuric acid method, while the activities of the biosynthetic enzymes were determined spectrophotometrically by measuring the formation or disappearance of NAD(P)H at 340 nm. An environmental pH of 5.0, using galactose as carbon source, markedly improved not only polymer production and yield but also, cell growth and lactic acid production. Analysis of the activities of the EPS precursor-forming enzymes revealed that polysaccharide synthesis was correlated with uridine-diphosphate (UDP)-glucose pyrophosphorylase and UDP-galactose 4-epimerase under these growth conditions. CONCLUSIONS: EPS synthesis by Lact. casei CRL 87 was considerably improved at a controlled pH of 5.0 with galactose as carbon source, and was correlated with the activity of UDP-glucose pyrophosphorylase and UDP-galactose 4-epimerase. The results obtained with the wild-type and EPS- strains suggest that UDP-galactose 4-epimerase plays an essential role in EPS formation. SIGNIFICANCE AND IMPACT OF THE STUDY: Unravelling the key enzymes involved in EPS biosynthesis under optimum culture conditions for polymer production provides important information for the design of strategies, via genetic engineering, to enhance polysaccharide formation.

Effect of medium composition and temperature and pH changes on exopolysaccharide yields and stability during Streptococcus thermophilus LY03 fermentations.

To increase the exopolysaccharide (EPS) yields from Streptococcus thermophilus LY03 and to unravel the nature of the EPS degradation process, fermentation experiments were carried out with this strain in a customized MRS medium, using different additional carbohydrates or amino acids possibly related to growth and EPS production. No significant increase of the EPS yields or activities of the enzymes alpha-phosphoglucomutase, UDP-glucose pyrophosphorylase and UDP-galactose 4-epimerase that are correlated with EPS production, or of the activity of dTDP-glucose pyrophosphorylase involved in the rhamnose synthetic branch of EPS biosynthesis, was observed. The EPS monomer composition remained unchanged for all experiments. Fermentations with a sudden temperature increase or lowered pH were carried out as well to try to avoid EPS degradation upon prolonged fermentation. It was demonstrated that EPS degradation took place enzymatically. Incubations of purified high-molecular-mass EPS with cell-free culture supernatant or cell extracts showed its degradation by enzymes with an endo-activity. This glycohydrolytic activity probably encompasses several enzymes having a molecular mass lower than 50,000 and 10,000 Da, and seems to be rather stable at high temperature and low pH. These results contribute to a better understanding of the physiological and chemical factors influencing EPS production and degradation.

Effect of galactose and glucose on the exopolysaccharide production and the activities of biosynthetic enzymes in Lactobacillus casei CRL 87.

AIMS: The objective of this work was to study the influence of the sugar source on exopolysaccharide (EPS) production and the activities of the enzymes involved in the synthesis of sugar nucleotides in Lactobacillus casei CRL 87. The relationship between these enzymes and EPS formation was determined. METHODS AND RESULTS: The concentration of EPS was estimated by the phenol/sulphuric acid method while the chemical composition of purified EPS was investigated using gas-liquid chromatography. Biosynthetic enzyme activities were determined spectrophotometrically by measuring the formation or disappearance of NAD(P)H at 340 nm. Polysaccharide production by Lb. casei CRL 87 was 1.7 times greater on galactose than on glucose. The isolated polymer was composed of rhamnose, glucose and galactose. The activities of uridine-diphosphate (UDP)-glucose-pyrophosphorylase, thymidine-diphosphate (dTDP)-glucose-pyrophosphorylase and the dTDP-rhamnose-synthetic enzyme system were higher in galactose-grown than in glucose-grown cells. When an EPS- mutant strain was used, galactokinase activity was not detected on galactose, this sugar not being available for the formation of sugar nucleotides for further EPS production. dTDP-glucose-pyrophosphorylase and dTDP-rhamnose-synthetic enzyme system activities were lower than the values found for the wild type strain. CONCLUSION: The carbon source present in the culture medium affects EPS production by Lb. casei CRL 87. The greater polymer synthesis by galactose-grown cells is correlated with the higher UDP-glucose-pyrophosphorylase, dTDP-glucose-pyrophosphorylase and dTDP-rhamnose-synthetic enzyme system activities. Initial sugar metabolism is also an important step for the synthesis of EPS precursors by this strain. SIGNIFICANCE AND IMPACT OF THE STUDY: Knowledge of the effect of the sugar source on EPS production and the activities of biosynthetic enzymes provides information about the mechanisms of regulation of the synthesis of EPS which can contribute to improving polymer production.

Blood donors with 'medium' or 'minor' risk factors for human immunodeficiency virus infection: are they eligible for donation?

BACKGROUND AND OBJECTIVES: We conducted a longitudinal prospective study to assess the eligibility to blood donation of donors with 'minor' risk factors (i.e. minor surgery, professional exposure, cohabitation with 'high risk' people, occasional use of light drugs) or 'medium' risk factors for human immuno-deficiency virus (HIV) infection (i.e. casual sexual relationship, multiple heterosexual exposure, sexual partnership with subjects at risk, regular use of light drugs). DESIGN AND METHODS: During a 4-year period we administered a psychosocial questionnaire to all donors attending our Center. In addition we determined anti-HIV, anti-hepatitis C virus (HCV), hepatitis B surface antigen (HBsAg) and syphilis serology (TPHA) at entry to the study and at 6-month intervals. RESULTS: Of 25,367 donors, 1,535 (6%) reported medium and 8,761 (34%) minor risk. At enrollment into the study, 4 medium risk donors were anti-HIV positive and there was a significantly higher rate of positivity for TPHA (0.33% vs 0.07%) and anti-HCV (1.17% vs 0.63%) in this group than in donors reporting no risk. No anti-HIV positivity was observed in minor or no risk donors. During a median follow-up of 18 months, none of 24,404 donors undergoing 106,503 visits seroconverted to HIV. The incidences of novel HCV and syphilis infections were almost one log greater in donors at medium risk (3 and 1x10-4/yr, respectively) than in no risk donors (0.4 and 0.1x10-4/yr, respectively). Medium risk donors were more frequently males (Odds Ratio=3.2, 95% confidence interval= 2.8-3.7), aged 26-35 yrs (1.52; 1.3-1.78), single (1.4; 1.2-1.6), divorced (2; 1.4-2.8), freelance workers (1.43; 1.1-1.9) and first-time donors (1.8; 1.6-2.1) than no risk donors. INTERPRETATION AND CONCLUSIONS: The only 4 HIV positive subjects of the cohort were medium risk donors picked up at enrollment. No HIV seroconversion was observed during the study. On the basis of this study we will continue to defer 'medium' risk donors.

Sustained response to interferon-alpha2a monotherapy of young blood donors with minimal-to-mild chronic hepatitis C. The Donor Surveillance Study Group.

Subjects with minimal-to-mild chronic hepatitis C may suffer long-term consequences of hepatitis C virus (HCV) infection. Nonetheless, they are not candidates for antiviral treatment, mainly because little data are available concerning the efficacy and safety of therapy. Thirty-two HCV RNA positive individuals aged 18-45 years, who had a histological activity index score < or = 8 and alanine aminotransferase (ALT) levels < or = 1.5 times lower than the normal limit for at least 1 year, were prospectively enrolled among a cohort of 35358 candidate blood donors, and treated with 4.5 mega units (MU) of recombinant interferon-alpha2a (IFN-alpha2a) thrice weekly for 6 months, and for an additional 6 months if a virological response was observed. Twelve months after the completion of treatment, 13 of 31 evaluable patients were HCV RNA negative, accounting for a sustained response rate of 42%. Patients without fibrosis had a lower response rate than those with mild fibrosis (two of 14 vs 11 of 17; P=0.012). In responders, median aminotransferase levels were significantly lower after therapy than before (11.04 +/- 3.98 vs 27.3 +/- 12.32 U l-1, respectively; P < 0. 005). When the analysis was limited to the six responders whose pretreatment aminotransferase levels were consistently normal, this difference was still significant (9.33 +/- 4.12 vs 20.58 +/- 6.73 U l-1; P=0.002). In conclusion, a durable suppression of viraemia can be obtained by IFN monotherapy in a relatively high proportion of young subjects with minimal-to-mild chronic hepatitis C, especially when portal fibrosis is found on liver biopsy. The disappearance of viraemia always leads to a reduction in the degree of hepatocellular necrosis.

A multicenter prospective study on the risk of acquiring liver disease in anti-hepatitis C virus negative patients affected from homozygous beta-thalassemia.

Although the risk of transfusion-transmitted hepatitis has been recently reduced, transfusion-dependent beta-thalassemia patients may still develop liver disease due to viral infection or iron overload. We assessed the frequency and causes of liver dysfunction in a cohort of anti-hepatitis C virus (HCV) negative thalassemics. Of 1,481 thalassemics enrolled in 31 centers, 219 (14.8%) tested anti-HCV- by second-generation assays; 181 completed a 3-year follow-up program consisting of alanine-aminotransferase (ALT) measurement at each transfusion and anti-HCV determination by third-generation enzyme-immunoassay (EIA-3) at the end of study. Serum ferritin levels were determined at baseline and at the end of follow-up. Ten patients were anti-HCV+ by EIA-3 at the end of follow-up. Of them, seven were already positive in 1992 to 1993 when the initial sera were retested by EIA-3, one tested indeterminate by confirmatory assay, and two had true seroconversion (incidence, 4. 27/1,000 person years; risk of infection, 1/7,100 blood units, 95% confidence interval [CI], 1 in 2,000-1 in 71,000 units). At baseline, 67 of 174 thalassemics had abnormal ALT. Of those with normal ALT, seven subsequently developed at least one episode of moderate ALT increase (incidence, 24.6/1,000 person-years). All of the 20 patients with ferritin values >/=3,000 ng/mL had clinically relevant ALT abnormalities, as compared with 53 of 151 with <3,000 ng/mL (P < .005). Hepatic dysfunction is still frequent in thalassemics. Although it is mainly attributable to siderosis and primary HCV infection, the role of undiscovered transmissible agents cannot be excluded.