Improved production of 3‐hydroxypropionaldehyde by complex formation with bisulfite during biotransformation of glycerol

3‐Hydroxypropionaldehyde (3HPA) is an important specialty chemical which can be produced from glycerol using resting cells of Lactobacillus reuteri. This biocatalytic route, however, suffers from substrate‐ and product‐mediated loss of enzyme activity within 2 h of biotransformation. In order to overcome the inhibitory effects of 3HPA, complex formation with sodium bisulfite was investigated, optimized and applied for in situ capture of the aldehyde during biotransformation of glycerol in a fed‐batch process. As a result, the activity of the cells was maintained for at least 18 h. The 3HPA produced per gram cell dry weight was increased 5.7 times compared to the batch production process, and 2.2 times compared to fed‐batch process without in situ complex formation. This approach may have potential for production and in situ removal of 3HPA after further process development. Biotechnol. Bioeng. 2013; 110: 1243–1248. © 2012 Wiley Periodicals, Inc.     

Growth and nutrients accumulation potentials of giant reed (Arundo donax L.) in different habitats in Egypt

Arundo donax L. has a high biomass production and a tendency toward community dominance in many habitats and thereby a tolerance to a wide range of environmental conditions. Therefore, the present study investigated the potentiality of A. donax to accumulate nutrients and trace metals in its biomass. Six main habitats (Nile Bank, Drain Bank, Canal Bank, Field Edges, Railways and Roadsides) were recognized. At each habitat, six quadrats (each 1 m²), distributed equally in two sites, were selected for growth measurements (e.g., density, shoot height, diameter, leaf area and biomass), plant and soil analyses. Plants from Nile, Canal and Drain Banks had the highest values of most growth measurements, while those from Railways and Roadsides had the lowest. Canal Bank plants accumulated the highest concentrations of P, Cu and Pb in their leaves; Zn in the stem; and Mg, Cd and Fe in the rhizome. The bioaccumulation factor (BF) of A. donax, for Cd, Fe, Mn and Zn, was greater than 1, while the translocation factor (TF) of most trace metals was less than unity in most habitats. In conclusion, A. donax showed morphological plasticity in response to habitat heterogeneity, and its growth was most vigorous in the riparian habitats. The high BF, as well as the significant positive correlations between trace metals, especially Cd, in soil and plant, renders A. donax a powerful phytoremediator.     

Pistacia lentiscus fruit oil reduces oxidative stress in human skin explants caused by hydrogen peroxide

We investigated the efficacy of Pistacia lentiscus fruit oil (PLFO) for protecting human skin from damage due to oxidative stress. PLFO contains natural antioxidants including polyphenols, sterols and tocopherols. We compared the antioxidant potential of PLFO with extra virgin olive oil (EVOO). Explants of healthy adult human skin were grown in culture with either PLFO or EVOO before adding hydrogen peroxide (H₂O₂). We also used cultured skin explants to investigate the effects of PLFO on lipid oxidation and depletion of endogenous antioxidant defense enzymes including glutathione peroxidase (GPx), superoxide dismutase (SOD) and catalase (CAT) one day after 2 h exposure to H₂O₂. We found that PLFO scavenged radicals and protected skin against oxidative injury. PLFO exhibited greater antioxidant and free radical scavenging activity than EVOO. Skin explants treated with PLFO inhibited H₂O₂ induced MDA formation by inhibition of lipid oxidation. In addition, the oil inhibited H₂O₂ induced depletion of antioxidant defense enzymes including GPx, SOD and CAT. We found that treatment with PLFO repaired skin damage owing to its antioxidant properties.     

Dynamic modification of a mutant cytoplasmic cysteine residue modulates the conductance of the human 5-HT3A receptor

Structural models suggest that Arg(436) lies within five cytoplasmic portals of the 5-HT(3A) receptor. We tested both the accessibility of residue 436 and the influence of its charge on single channel conductance (gamma) by substituting Arg(436) with Cys and examining the effect of methanethiosulfonate (MTS) reagents on gamma. Inclusion of positively charged 2-aminoethyl-MTS (MTSEA) within the electrode solution reduced gamma of 5-HT(3A)(R436C) receptors in outside-out patches from 7.8 +/- 0.5 to 5.0 +/- 0.5 picosiemens (pS). To increase gamma, we substituted Arg(436) by Cys in the 5-HT(3A)(R432Q,R440A) mutant, yielding the 5-HT(3A)(QCA) construct with a gamma of 17.7 +/- 0.4 pS. Modification of 5-HT(3A)(QCA) receptors by MTSEA or 2-(trimethylammonium) ethyl-MTS reduced gamma to 8.7 +/- 0.5 and 6.7 +/- 0.4 pS, respectively, both significantly below that of channels exposed to nonpolar propyl-MTS. Extracellular MTSEA, but not 2-(trimethylammonium) ethyl-MTS, crossed the membrane and in so doing slowly (tau = 94 s) reduced gamma. MTSEA more rapidly (tau = 15 s) reduced the gamma of 5-HT(3A)(QCA) receptors in inside-out patches, an effect reversed by the reducing agent dithiothreitol. Cys(436) modification by negatively charged 2-carboxyethyl-MTS and 2-sulfonatoethyl-MTS increasedgamma to 23 +/- 1.0 and 26 +/- 0.7 pS, respectively. MTS reagents did not affect gamma values for 5-HT(3A)(QDA) constructs with Cys substituted for Lys(431) predicted to be outside the entrance to the portals. Collectively, the data demonstrate that the dynamic modification of the charge of a cytoplasmic residue regulates gamma, consistent with the existence of cytoplasmic portals that impose a rate-limiting barrier to ion conduction in Cys loop receptors.     

In vitro effect of pH and ethanol on biofilm formation by clinicalica-positiveStaphylococcus epidermidis strains

Biofilm production is an important step in the pathogenesis ofStaphylococcus epidermidis associated biomaterial infections.Staphylococcus epidermidis strains isolated from dialysis fluid (n=9) and needle cultures (n=14) were phenotyped and genotyped for extracellular polysaccharide production and were examined for their ability to produce slime in a medium at various pH levels (3, 5, 7, 9 and 12) and with ethanol supplementation (0, 2, 5, 10 and 15%) using a semi-quantitative adherence assay. A total of 23 clinicalicaADBC positiveS. epidermidis, one reference strain (S. epidermidis CIP 106510) used as positive control, and oneicaADBC negative strain (E21) were investigated. Qualitative biofilm production analysis revealed that 15 of the 23icaADBC positive strains (65.21%) produced slime on Congo Red agar plates. Quantitative biofilm was determined by measuring the optical density at 570 nm (OD₅₇₀). The results show that the slime production depended on the pH value of the medium and the ethanol concentration. At highly acidic (pH 3) and alkaline (pH 12) levels, the OD₅₇₀ was lower, while at pH 7 the adhesion was moderate. In addition the cells adhered strongly with 2% ethanol than with the other concentrations. Our results suggest that pH and ethanol were stress factors that led toS. epidermidis biofilm formation and also play a possible role in the pathogenesis of biomaterial-related infections.     

Autophagy and senescence: A new insight in selected human diseases

Senescence and autophagy play important roles in homeostasis. Cellular senescence and autophagy commonly cause several degenerative processes, including oxidative stress, DNA damage, telomere shortening, and oncogenic stress; hence, both events are known to be interrelated. Autophagy is well known for its disruptive effect on human diseases, and it is currently proposed to have a direct effect on triggering senescence and quiescence. However, it is yet to be proven whether autophagy has a positive or negative impact on senescence. It is known that elevated levels of autophagy induce cell death, whereas inadequate autophagy can trigger cellular senescence. Both have important roles in human diseases such as aging, renal degeneration, neurodegenerative disorders, and cancer. Therefore, this review aims to highlight the relevance of senescence and autophagy in selected human ailments through a summary of recent findings on the connection and effects of autophagy and senescence in these diseases.     

Membrane structural perturbations caused by anesthetics and nonimmobilizers: a molecular dynamics investigation.

The structural perturbations of the fully hydrated dimyristoyl-phosphatidylcholine bilayer induced by the presence of hexafluoroethane C(2F6), a "nonimmobilizer," have been examined by molecular dynamics simulations and compared with the effects produced by halothane CF3CHBrCl, an "anesthetic," on a similar bilayer (DPPC) (Koubi et al., Biophys. J. 2000. 78:800). We find that the overall structure of the lipid bilayer and the zwitterionic head-group dipole orientation undergo only a slight modification compared with the pure lipid bilayer, with virtually no change in the potential across the interface. This is in contrast to the anesthetic case in which the presence of the molecule led to a large perturbation of the electrostatic potential across to the membrane interface. Similarly, the analysis of the structural and dynamical properties of the lipid core are unchanged in the presence of the nonimmobilizer although there is a substantial increase in the microscopic viscosity for the system containing the anesthetic. These contrasting perturbations of the lipid membrane caused by those quite similarly sized molecules may explain the difference in their physiological effects as anesthetics and nonimmobilizers, respectively.