Modified Lysozymes as Novel Broad Spectrum Natural Antimicrobial Agents in Foods

In recent years much attention and interest have been directed toward application of natural antimicrobial agents in foods. Some naturally occurring proteins such as lactoperoxidase, lactoferrin, and lysozyme have received considerable attention and are being considered as potential antimicrobial agents in foods. Lysozyme kills bacteria by hydrolyzing the peptidoglycan layer of the cell wall of certain bacterial species, hence its application as a natural antimicrobial agent has been suggested. However, limitations in the action of lysozyme against only Gram‐positive bacteria have prompted scientists to extend the antimicrobial effects of lysozyme by several types of chemical modifications. During the last 2 decades extensive research has been directed toward modification of lysozyme in order to improve its antimicrobial properties. This review will report on the latest information available on lysozyme modifications and examine the applicability of the modified lysozymes in controlling growth of Gram‐positive and Gram‐negative bacteria in foods. The results of modifications of lysozyme using its conjugation with different small molecule, polysaccharides, as well as modifications using proteolytic enzymes will be reviewed. These types of modifications have not only increased the functional properties of lysozyme (such as solubility and heat stability) but also extended the antimicrobial activity of lysozyme. Many examples will be given to show that modification can decrease the count of Gram‐negative bacteria in bacterial culture and in foods by as much as 5 log CFU/mL and in some cases essentially eliminated Escherichia coli. In conclusion this review demonstrates that modified lysozymes are excellent natural food preservatives, which can be used in food industry.     

Lattice Boltzmann simulation of double diffusive natural convection in a square cavity with a hot square obstacle

Double diffusion convection in a cavity with a hot square obstacle inside is simulated using the lattice Boltzmann method. The results are presented for the Rayleigh numbers 104,105 and 106, the Lewis ...     

Antitumour activity of S-p-bromobenzylglutathione cyclopentyl diester in vitro and in vivo. Inhibition of glyoxalase I and induction of apoptosis

The glyoxalase I inhibitor diester, S-p-bromobenzyl-glutathione cyclopentyl diester (BrBzGSHCp2), inhibited the growth of human leukaemia 60 (HL60) cells in vitro. The median growth inhibitory concentration GC50 value of BrBzGSHCp2 was 4.23 +/- 0.001 microM (n = 21), and the median toxic concentration TC50 value was 8.86 +/- 0.01 microM (n = 21). BrBzGSHCp2 inhibited DNA synthesis in the third hr of incubation: the median inhibitory concentration IC50 value was 6.11 +/- 0.02 microM (n = 8). Incubation of HL60 cells with 10 microM BrBzGSHCp2 delivered the diester into cells: de-esterification of the diester there in lead to formation of the S-p-bromobenzylglutathione, inhibition of glyoxalase I activity in situ, increase in the methylglyoxal concentration after 1 hr, and induction of apoptosis after 6 hr. BrBzGSHCp2 (50-200 mg/kg) also inhibited the growth of murine adenocarcinoma 15A in vivo. Glyoxalase I inhibitor diesters may, therefore, inhibit tumour growth by inducing the accumulation of methylglyoxal in tumour cells, and induction of apoptosis.     

Intermittent thermal fusion.

Conducted a study of intermittent thermal stimulation with 4 male 17-29 yr olds to test the effect of input factors analogous to those that have proven significant in varying critical flicker fusion thresholds for vision. Amount of area stimulated, intensity level, and pulse-to-cycle fraction were tested separately, while other factors were held constant. stimulation was applied to the 2 body areas of the upper back and the volar forearm. Results of variation of thermal stimulation, termed thermal flicker fusion (TFF), show general correspondence to the functions produced by varying similar parameters in the visual modality. Current TFF results are compared with previous fusion studies in the thermal and other modalities, and a theoretical explanation is suggested. (French summary) (26 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Fluorescein isothiocyanate‐dyed mesoporous silica nanoparticles for tracking antioxidant delivery

This study investigated the cellular uptake of fluorescein isothiocyanate‐labelled mesoporous silica nanoparticles (FITC‐MSNs), amine‐functionalised FITC‐MSNs (AP‐FITC‐MSNs) and their gallic acid (GA)‐loaded counterparts. Mesoporous silica nanoparticles were labelled with fluorescein isothiocyanate, functionalised by 3‐aminopropyltriethoxysilane (APTES) (AP‐FITC‐MSNs) and then loaded by GA. All nanoparticles were characterised by transmission electron microscopy (TEM), Fourier transform infrared spectroscopy, and X‐ray diffraction. The cytotoxicity of different concentrations of dyed nanoparticles was investigated using (3‐(4,5‐trihydroxybenzoic acid, dimethylthiazol‐2‐yl)‐2,5‐diphenyltetrazolium bromide) assay and flow cytometry. TEM images showed that the average particle sizes of FITC‐MSNs and AP‐FITC‐MSNs were about 100 and 110 nm, respectively. These nanoparticles were internalised by Caco‐2 cells, accumulated and dispersed into the cytoplasm, nucleus, and subcellular organelles. Nanoparticles containing GA clearly decreased the viability of cells. FITC‐MSNs showed no toxicity on Caco‐2 cells at concentrations of ≤50 µg/ml. Functionalisation of FITC‐MSNs using APTES decreased toxicity effects on the cells. It was found that FITC‐MSNs can be applied at low concentrations as a marker in the cells. In addition, AP‐FITC‐MSNs showed better biocompatibility with Caco‐2 cells than FITC‐MSNs, because of their positive surface charges.Inspec keywords: mesoporous materials, porosity, nanoparticles, dyes, silicon compounds, nanocomposites, nanofabrication, nanomedicine, cellular biophysics, molecular biophysics, biochemistry, transmission electron microscopy, Fourier transform infrared spectra, X‐ray diffraction, toxicology, particle size, biomedical materials, surface charging, cancerOther keywords: fluorescein isothiocyanate‐dyed mesoporous silica nanoparticles, antioxidant delivery tracking, cellular uptake, amine‐functionalised FITC‐MSNs, gallic acid‐loaded counterparts, 3‐aminopropyltriethoxysilane, transmission electron microscopy, TEM, Fourier transform infrared spectroscopy, X‐ray diffraction, cytotoxicity, dyed nanoparticles, (3‐(4,5‐trihydroxybenzoic acid‐dimethylthiazol‐2‐yl)‐2,5‐diphenyltetrazolium bromide) assay, flow cytometry, particle sizes, AP‐FITC‐MSNs, Caco‐2 cells, cytoplasm, subcellular organelles, cell viability, biocompatibility, positive surface charges, SiO₂      

Fate of copper in submerged membrane bioreactors treating synthetic municipal wastewater

This paper assesses the impact of copper on the performance of two membrane bioreactors (MBR) treating municipal wastewater at a hydraulic retention time (HRT) of 4h, and solids residence times (SRT) of 20 days, at influent copper concentrations of 0.2-8 mg Cu/L. The addition of copper resulted in a significant increase in soluble microbial products (SMPs), and a predominance of >100 kDa molecular weight SMPs. The study showed that in well-buffered wastewaters, complete nitrification was achieved at total copper concentrations as high as 840 mg/L or 10% of the mixed liquor volatile suspended solids. MINTEQ simulation showed that most of the copper (99.8%) in the MBR was in the form of inorganic copper precipitates, with free Cu2+ and total soluble copper in the range of 0.0-0.11 and 0.1-0.82 mg/L, respectively.     

A convenient one-pot synthesis of thiopyrano[4,3-b]pyran derivatives under LiOH·H2O/EtOH/ultrasonic conditions

Various derivatives of thiopyrano[4,3-b]pyran structure are synthesized via a multicomponent procedure starting from tetrahydro-4H-thiopyran-4-one, aromatic aldehydes, and malononitrile. Reactions take place by the use of catalytic quantities of LiOH·H₂O in one pot under ultrasonic conditions and in an ethanolic medium. Isolation of products occurs by spontaneous precipitation in reaction mixtures and no cumbersome and expensive chromatographic separations are needed.     

Simulation of methane steam reforming in a catalytic micro-reactor using a combined analytical approach and response surface methodology

In this study, a steady-state analytical model for heat and mass transfer in a 2D micro-reactor coated with a Nickel-based catalyst is developed to investigate microscale hydrogen production. Appropriate correlations for each species’ net rate of production or consumption, mass diffusivity, and the heat of reactions are developed using a detailed reaction mechanism of methane steam reforming. The energy and species conservation equations are then solved for the reactive mixture coupled with the wall energy equation. Finally, the response surface methodology (RSM) is employed to study the effects of channel height, inlet velocity and temperature, wall thickness and conductivity, and external heat flux on CH4 conversion. It is found that the inlet gas temperature, among different parameters, has the most influence on the overall performance of the microchannel hydrogen production. Also, the maximum necessary heat of reforming reaction increases by 84% and 26% if the CH₄ conversion changes from 50% to 60% and 60% to 70%, respectively. The developed analytical simulation can be a useful tool for designing experiments in micro-scale hydrogen production.     

Kinetics and Microstructural Investigation of High-Temperature Oxidation of IN-738LC Super Alloy

The present study was carried out to investigate the kinetics and the surface chemistry of the oxide layers formed on the IN-738LC super alloy during high-temperature oxidation at 950 °C in air from 1 to 260 h. Oxidation kinetics were studied by mass gain measurement. The oxide layers were characterized by field emission scanning electron microscope, elemental distribution map, energy-dispersive spectroscopy as well as x-ray diffractometry (XRD). The oxidation kinetics followed the parabolic law. The XRD analysis revealed that the oxide scale contained mainly NiO, Ni (Cr, Al)₂O₄, Al₂O₃, TiO₂ and Cr₂O₃. The oxide structure, from the top surface down to the substrate, was clarified by elemental map distribution studies as Ni-Ti oxides, Cr-Ti oxides, Cr₂O₃ oxide band, Ni-Co-Cr-W oxide and finally a blocky Al₂O₃ region. The oxidation scales were composed of three distinct layers of the outer and mid layers enriched by TiO₂ and Cr₂O₃, NiCr₂O₄ oxide, respectively, and the innermost layer was composed of Al₂O₃ and matrix alloy. The depleted gamma prime layer was formed under the oxidation scales due to the impoverishment of Al and Ti which were induced by the formation of Al₂O₃ and TiO₂.     

Stabilization of mode-locked trains,and dark resonance of two-photon lambda-level structures

Our ultimate objective is to design a combined frequency standard for optical as well as radio frequencies. A mode-locked laser provides frequency components that can be used as a ruler to measure any unknown optical source through direct beating. The frequency spacing of a pair of teeth of this comb is in itself a radio frequency reference. Fast control and correction for both the average frequency and the repetition rate of a mode-locked Ti : sapphire laser are achieved by locking the laser to a reference cavity of ultra-low expansion quartz with equal mode spacing. We measure an optical frequency with a mean square deviation of 700 Hz, instability limited by the radio-frequency sources used to count the repetition rate. As a reference standard to achieve absolute accuracy, we use the Λ transition 5S^1/2 (F = 1) → 5D^5/2 (F = 3) → 5S^1/2 (F = 2) of rubidium. The theory for this coherent interaction shows that, with one mode resonant with the two-photon 5S^1/2 (^F = 1) → 5D^5/2 (^F = 3) transition, the fluorescence goes through a resonance for a change in repetition rate of less than 10 kHz. These results suggest that, by locking to the peak of that resonant feature, optical stability and absolute accuracy better than 1 kHz can easily be achieved.