Biosurfactant production under extreme environmental conditions by an efficient microbial consortium, ERCPPI-2

The biosurfactant production potential of a new microbial consortium of Enterobacter cloacae and Pseudomonas sp. (ERCPPI-2) which was isolated from heavy crude oil-contaminated soil in the south of Iran, has been investigated under extreme environmental conditions. The isolated consortium produces a biosurfactant mixture with excessive oil spreading and emulsification properties. This consortium was able to grow and produce biosurfactant at temperatures up to 70 °C, pressures up to 6000 psia, salinities up to 15% (w/v), and in the pH range 4-10. Besides, the optimum biosurfactant production conditions were found to be 40 °C and 7.0 for the temperature and pH value, respectively. These conditions gave the best biosurfactant production of 1.74 g/1 when the cells were grown on a minimal salt medium containing 1.0% (w/v) olive oil, 1.0% (w/v) sodium nitrate supplemented with 1.39% (w/v) K(2)HPO(4) at 40 °C and 150 rpm after 48 h of incubation. The ERCPPI-2 could reduce surface and interfacial tensions to 31.7 and 0.65 mN/m from the original values of 58.3 and 16.9 mN/m, respectively. The isolated consortium produced biosurfactant using heavy crude oil as the sole source of carbon and emulsified the available heavy crude oil up to E(24)=83.4%. The results of the core holder flooding tests at simulated reservoir conditions demonstrated that the oil recovery efficiency due to the injection of the cell-free biosurfactant solution was 27.2%, and the bacterium injection reduced the final residual oil saturations to below 3% at optimum conditions.     

Formation of a mesoscopic skin barrier in mesoglobules of thermoresponsive polymers

With the combination of molecular scale information from electron paramagnetic resonance (EPR) spectroscopy and meso-/macroscopic information from various other characterization techniques, the formation of mesoglobules of thermoresponsive dendronized polymers is explained. Apparent differences in the EPR spectra in dependence of the heating rate, the chemical nature of the dendritic substructure of the polymer, and the concentration are interpreted to be caused by the formation of a dense polymeric layer at the periphery of the mesoglobule. This skin barrier is formed in a narrow temperature range of ~4 K above T(C) and prohibits the release of molecules that are incorporated in the polymer aggregate. In large mesoglobules, formed at low heating rates and at high polymer concentrations, a considerable amount of water is entrapped that microphase-separates from the collapsed polymer chains at high temperatures. This results in the aggregates possessing an aqueous core and a corona consisting of collapsed polymer chains. A fast heating rate, a low polymer concentration, and hydrophobic subunits in the dendritic polymer side chains make the entrapment of water less favorable and lead to a higher degree of vitrification. This may bear consequences for the design and use of thermoresponsive polymeric systems in the fast growing field of drug delivery.     

One-pot synthesis of functionalized 4-oxo-2-thioxo-1,3-thiazinanes from primary amines,CS2, and itaconic anhydride

An efficient synthesis of 2-(3-alkyl-4-oxo-2- thioxo-1,3-thiazinan-5-yl)acetic acids is described via a three-component reaction between primary amines, CS₂, and itaconic anhydride.     

Naturally reductive homogeneous Randers spaces

In this paper, we study naturally reductive Randers metrics on homogeneous manifolds. We first prove that naturally reductive Randers metrics are of Berwald type. We then give an explicit formula for the flag curvature of naturally reductive Randers metrics. Finally a necessary and sufficient condition for invariant Randers metrics on homogeneous manifolds being naturally reductive is given.     

Effect of low-salinity water on asphaltene precipitation

The effect of low-salinity (1000 to 5000?ppm) and intermediate-salinity (5000 to 40000?ppm) water (MgSO₄, MgCl₂, Na₂SO₄, CaCl₂, NaCl and KCl) on asphaltene precipitation was investigated in this work. The results revealed that all brines intensify the amount of asphaltene precipitation. All cases exhibited initial downward trend followed by the upward trend for the amount of asphaltene precipitation with increasing the brine concentration. A similar trend was also observed for Interfacial Tension (IFT) between crude oil and brine in this study. IFT was tested for MgSO₄, MgCl₂, Na₂SO₄, CaCl₂, NaCl and KCl brines with concentrations of 1000 to 40000?ppm. Finally, experimental results showed that an increase in volume of all brines in the mixture (brine +oil) led to increase and decrease of the asphaltene precipitation in low and intermediate salinity regions, respectively.     

Tuning Human Serum Albumin (HSA) Hydrogels through Albumin Glycation

The changes of technological properties of albumin-based hydrogels induced by increasing degrees of post-translational modification of the protein are reported. Maillard-type modification of amino acids arginine and lysine of albumin is achieved through glyoxal as an α-dicarbonyl compound. The degrees of modification are fine-tuned using different molar ratios of glyoxal. Hydrogels are thermally induced by heating highly concentrated precursor solutions above the protein's denaturation temperature. While the post-translational modifications are determined and quantified with mass spectrometry, continuous-wave (CW) electron paramagnetic resonance (EPR) spectroscopy shed light on the protein fatty acid binding capacity and changes thereof in solution and in the gel state. The viscoelastic behavior is characterized as a measure of the physical strength of the hydrogels. On the nanoscopic level, the modified albumins in low concentration solution reveal lower binding capacities with increasing degrees of modification. On the contrary, in the gel state, the binding capacity remains constant at all degrees of modifications. This indicates that the loss of fatty acid binding capacity for individual albumin molecules is partially compensated by new binding sites in the gel state, potentially formed by modified amino acids. Such, albumin glycation offers a fine-tuning method of technological and nanoscopic properties of these gels.