Improvement of biodesulfurization rate by assembling nanosorbents on the surfaces of microbial cells

To improve biodesulfurization rate is a key to industrialize biodesulfurization technology. The biodesulfurization rate is partially affected by transfer rate of substrates from organic phase to microbial cell. In this study, gamma-Al2O3 nanosorbents, which had the ability to selectively adsorb dibenzothiophene (DBT) from organic phase, were assembled on the surfaces of Pseudomonas delafieldii R-8 cell, a desulfurization strain. gamma-Al2O3 nanosorbents have the ability to adsorb DBT from oil phase, and the rate of adsorption was far higher than that of biodesulfurization. Thus, DBT can be quickly transferred to the biocatalyst surface where nanosorbents were located, which quickened DBT transfer from organic phase to biocatalyst surface and resulted in the increase of biodesulfurization rate. The desulfurization rate of the cells assembled with nanosorbents was approximately twofold higher than that of original cells. The cells assembled with nanosorbents were observed by a transmission electron microscope.     

Bacteriophage SP50 as a marker for cell wall growth in Bacillus subtilis.

When grown under conditions of phosphate limitation, Bacillus subtilis W23 lacked wall teichoic acid and did not adsorb phage SP50. During transition from growth under conditions of phosphate limitation to those of potassium limitation, the bacteria developed an ability to adsorb phage which increased exponentially in relation to their content of wall teichoic acid. During transition in the reverse direction, the bacteria retained near-maximum phage-binding properties until their content of wall teichoic acid had fallen to a fairly low level. These observations suggest that newly incorporated wall material does not immediately appear at the cell surface in a structure to which phage can adsorb. Examination of the location of adsorbed phage particles showed that recently incorporated receptor material appeared at the cell surface first along the length of the cylindrical portion of the cell. The results are consistent with models of wall assembly in which newly synthesized wall material is intercalated at a large number of sites that are distributed along the length of the cell. This newly incorporated material may be located initially at a level underlying the surface of the cell and may become exposed at the surface only during subsequent growth. Incorporation of new material may also proceed rapidly into the developing septa, but new wall material is incorporated into existing polar caps more slowly, or perhaps not at all.     

Temperature dependence of the interfacial behavior of uracil derivatives.

The effect of temperature on the interfacial behavior of uracil, thymine and 1,5-dimethyluracil has been used to characterize the thermodynamics of adsorption of these compounds at a mercury electrode-aqueous electrolyte interface. Between 4.5 degrees C and 40 degrees C all three compounds exhibit two adsorption regions. The first, a dilute layer where the molecules adsorb in a flat orientation on the electrode surface. The second, a compact layer where the molecules adsorb in a perpendicular orientation. The thermodynamic constants characterizing formation of these surface layers have been deduced.     

Evidence that Bacillus subtilis Bacteriophage SPO2 is Temperate and Heteroimmune to Bacteriophage φ105

Some characteristics of Bacillus subtilis phage SPO2 which show that it is a temperate phage are presented. Wild-type SPO2 forms turbid plaques, similar to those of other temperate phages. SPO2 lysogenic strains which are resistant to SPO2 can be isolated; these strains remain stable lysogens despite the fact that they can no longer adsorb SPO2. SPO2 lysogenic strains can be grown for many generations in SPO2 antiserum and remain lysogenic. Phage SPO2 plates on phi105 lysogens and phage phi105 plates on SPO2 lysogens; this indicates that SPO2 and phi105 are heteroimmune. Phage phi105 plates on an SPO2-resistant strain; this indicates that SPO2 and phi105 adsorb to different receptor sites on the bacterial surface.     

Trypanosoma lewisi: accumulation of antigen-specific host IgG as a component of the surface coat during the course of infection in the rat.

Naturally acquired host IgG, adsorbed to the surface of Trypanosoma lewisi during the course of infection in the rat, was labeled with fluorescein-conjugated rabbit IgG, or Fab fragments of this IgG, directed against rat IgG. The intensity of fluorescent labeling increases with time, concomitant with the increase in anti-T. lewisi activity of host plasma. Trypanosomes harvested from immunosuppressed hosts lack detectable surface IgG. Trypanosomes having little or no detectable surface IgG (harvested from immunosuppressed hosts or early in the infection from immunocompetent hosts) can adsorb IgG from serum with ablastic activity only (obtained from other infected rats between the first and second crises and adsorbed to remove trypanocidal antibodies), but not from normal serum. Therefore, the absence of detectable surface IgG on such cells is not caused by the parasites' inability to adsorb host IgG, but rather results from the immune state of the host. Hence surface IgG on T. lewisi is specific antibody. Host albumin is nonspecifically adsorbed, in contrast to IgG. Trypanosomes from immuno-suppressed and immunocompetent rats were positive and visually indistinguishable from each other when labeled with anti-rat albumin, and were equally agglutinable with anti-rat albumin serum.     

Effect of Yeast Cell Morphology,Cell Wall Physical Structure and Chemical Composition on Patulin Adsorption

The capability of yeast to adsorb patulin in fruit juice can aid in substantially reducing the patulin toxic effect on human health. This study aimed to investigate the capability of yeast cell morphology and cell wall internal structure and composition to adsorb patulin. To compare different yeast cell morphologies, cell wall internal structure and composition, scanning electron microscope, transmission electron microscope and ion chromatography were used. The results indicated that patulin adsorption capability of yeast was influenced by cell surface areas, volume, and cell wall thickness, as well as 1,3-β-glucan content. Among these factors, cell wall thickness and 1,3-β-glucan content serve significant functions. The investigation revealed that patulin adsorption capability was mainly affected by the three-dimensional network structure of the cell wall composed of 1,3-β-glucan. Finally, patulin adsorption in commercial kiwi fruit juice was investigated, and the results indicated that yeast cells could adsorb patulin from commercial kiwi fruit juice efficiently. This study can potentially simulate in vitro cell walls to enhance patulin adsorption capability and successfully apply to fruit juice industry.     

Surface behavior,microheterogeneity and adsorption equilibrium of myelin at the air-water interface

Interfacial films of whole myelin membrane adsorb at the air-water interface from myelin vesicles. The films show a liquid state and their equilibrium spreading pressure is equal to the collapse pressure (about 47 mN/m). The films appear microheterogeneous as seen by epifluorescence microscopy, consisting in two liquid phases over all the adsorption isotherm, starting with rounded liquid expanded domains (low surface pressure) immersed in a cholesterol enriched phase and reaching a fractal pattern at high surface pressure similar to those previously observed by compressing the film. Vesicles adsorb to the interfacial film mainly at the lateral interfaces. The high surface pressure at equilibrium (almost equal to the collapse pressure) indicates the formation of surface multilayers, also shown by fluorescence microscopy.     

Zinc-decorated silica-coated magnetic nanoparticles for protein binding and controlled release

The aim of this study was to be able to reversibly bind histidine-rich proteins to the surface of maghemite magnetic nanoparticles via coordinative bonding using Zn ions as the anchoring points. We showed that in order to adsorb Zn ions on the maghemite, the surface of the latter needs to be modified. As silica is known to strongly adsorb zinc ions, we chose to modify the maghemite nanoparticles with a nanometre-thick silica layer. This layer appeared to be thin enough for the maghemite nanoparticles to preserve their superparamagnetic nature. As a model the histidine-rich protein bovine serum albumin (BSA) was used. The release of the BSA bound to Zn-decorated silica-coated maghemite nanoparticles was analysed using sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). We demonstrated that the bonding of the BSA to such modified magnetic nanoparticles is highly reversible and can be controlled by an appropriate change of the external conditions, such as a pH decrease or the presence/supply of other chelating compounds.     

Replication of viruses in a growing plaque: a reaction-diffusion model.

An understanding of the viral replication process commonly referred to as "plaque growth" is developed in the context of a reaction-diffusion model. The interactions among three components: the virus, the healthy host, and the infected host are represented using rates of viral adsorption and desorption to the cell surface, replication and release by host lysis, and diffusion. The solution to the full model reveals a maximum in the dependence of the velocity of viral propagation on its equilibrium adsorption constant, suggesting that conditions can be chosen where viruses which adsorb poorly to their hosts will replicate faster in plaques than those which adsorb well. Analytic expressions for the propagation velocity as a function of the kinetic and diffusion parameters are presented for the limiting cases of equilibrated adsorption, slow adsorption, fast adsorption, and large virus yields. Hindered diffusion at high host concentrations must be included for quantitative agreement with experimental data.     

Droplet enrichment factors of pigmented and nonpigmented Serratia marcescens: possible selective function for prodigiosin

Drops produced by bursting bubbles provide a mechanism for the water-to-air transfer and concentration of matter. Bacteria can adsorb to air bubbles rising through bacterial suspensions and enrich the drops formed by the bubbles upon breaking, creating atmospheric biosols which function in dispersal. This bacterial enrichment can be quantified as an enrichment factor (EF), calculated as the ratio of the concentration of bacteria in the drop to that of the bulk bacterial suspension. Bubbles were produced in suspensions of pigmented (prodigiosin-producing) and nonpigmented cultures of Serratia marcescens. EFs for pigmented cultures were greater than EFs for nonpigmented cells. Pigmented cells appeared hydrophobic based on their partitioning in two-phase systems of polyethylene glycol 6000 and dextran T500. The surface hydrophobicity of pigmented cells may result from the hydrophobic nature of prodigiosin and could account for the greater ability of these bacteria to adsorb to air bubbles and enrich airborne droplets. Enhancement of the aerosolization of S. marcescens may be a selective function of the bacterial secondary metabolite prodigiosin.     

Droplet enrichment factors of pigmented and nonpigmented Serratia marcescens: possible selective function for prodigiosin.

Drops produced by bursting bubbles provide a mechanism for the water-to-air transfer and concentration of matter. Bacteria can adsorb to air bubbles rising through bacterial suspensions and enrich the drops formed by the bubbles upon breaking, creating atmospheric biosols which function in dispersal. This bacterial enrichment can be quantified as an enrichment factor (EF), calculated as the ratio of the concentration of bacteria in the drop to that of the bulk bacterial suspension. Bubbles were produced in suspensions of pigmented (prodigiosin-producing) and nonpigmented cultures of Serratia marcescens. EFs for pigmented cultures were greater than EFs for nonpigmented cells. Pigmented cells appeared hydrophobic based on their partitioning in two-phase systems of polyethylene glycol 6000 and dextran T500. The surface hydrophobicity of pigmented cells may result from the hydrophobic nature of prodigiosin and could account for the greater ability of these bacteria to adsorb to air bubbles and enrich airborne droplets. Enhancement of the aerosolization of S. marcescens may be a selective function of the bacterial secondary metabolite prodigiosin.     

Concentration of Enteroviruses on Membrane Filters

Enteroviruses can be made to adsorb or to pass through membrane filters by manipulation of the suspending medium. Salts facilitate virus adsorption, but membrane-coating components (MCC) interfere. Because cells release MCC into the culture medium during viral growth, MCC must be removed before virus can be adsorbed to membranes. Adsorbed virus can be eluted with diluents containing MCC (cell extracts or serum) or agents that reduce surface tension (sodium lauryl sulfate). By membrane adsorption and elution, enteroviruses can be readily concentrated and quantitatively recovered from crude virus harvests.     

Effectiveness and mechanisms of dye adsorption on a straw-based biochar

A biochar (BC) generated from straw as a cost-effective substitute for activated carbon (AC) was tested for its adsorptive ability toward reactive brilliant blue (KNR) and rhodamine B (RB). BC and AC had similar surface areas but differed in porosity, surface acidity and point of zero surface charge. The two carbons were highly effective adsorbents for both dyes at pH 3.0 and 6.5. BC was slightly more effective than AC to adsorb RB due to the RB–BC electrostatic interactions and RB protonation at low pH. The two carbons reversed in their effectiveness to adsorb KNR for similar reasons. The π–π interactions between dye molecules and graphene layers of BC, the direct dye-BC electrostatic attraction/repulsion and the intermolecular hydrogen bonding are proposed to be the combined mechanisms for dye adsorption. Rich phenolic hydroxyls on the surface of BC are expected to enhance the π–π interactions.     

石油焦基高比表面积活性炭对水中Pb2+离子吸附性能的研究

以石油焦基为原料,采用KOH活化法制取高比表面积活性炭。考察了高比表面积活性炭吸附水中Pb^2 时,pH值、Pb^2 浓度、吸附时间和活性炭用量等因素对Pb^2 吸附量和水中Pb^2 残余浓度的影响。实验结果表明：高比表面积活性炭在适宜条件下对Pb^2 具有较大的吸附量和良好的再生效果。为高比表面积活性炭在废水中的实际应用提供了理论依据。     

Surface and aggregate properties of an amphiphilic derivative of carboxymethylchitosan

A new kind of amphiphilic derivative of carboxymethylchitosan, a group of (2-hydroxyl-3-butoxyl)propylcarboxymethylchitosans (HBP-CMCHS), has been synthesized, and the surface and aggregate properties have been studied by means of surface tension, surface pressure and fluorescence measurements. HBP-CMCHS can adsorb on the surface to decrease the surface tension of the solution. The adsorption film was quite stable, which can make the relative compressed pressure increase dramatically with the decrease of the surface area. In solution, hydrophobic aggregations were identified by the decrease in the ratio of the fluorescence emission intensity of the first and third pyrene vibronic peaks ( I(1)/ I(3)). Results showed that the aggregation began to form at a concentration similar to that of the polymer transfer to the air-water interface. Aggregate formation of the polymers is a gradually compact process with hydrophobic associations. Increase of DS and addition of NaCl to the HBP-CMCHS solution can make the surface tension decrease, make the aggregation occur at lower concentration, and make the aggregation more hydrophobic.     

Hydrophobic interactions of Escherichia coli ribosomes

We have demonstrated the presence of hydrophobic sites on the surface of Escherichia coli ribosomes by means of hydrophobic chromatography on Octyl-Sepharose. Both 30-S and 50-S ribosomal subunits adsorb to Octyl-Sepharose at a low salt concentration, and can be eluted from it with a nonionic detergent without substantial changes in structure or activity. By testing a series of LiCl-derived ribosomal cores for their ability to adsorb to Octyl-Sepharose we have shown that the interaction of ribosomal particles with Octyl-Sepharose is dependent on the presence of certain ribosomal proteins; the core particles which lack these proteins do not bind to Octyl-Sepharose. The binding of a series of different ribosomal cores to nitrocellulose filters (Millipore) yielded the same pattern as was observed with Octyl-Sepharose, i.e. the more protein-depleted the particles, the less they were adsorbed. Thus, the adsorption of ribosomes to Millipore filters and to Octyl-Sepharose is presumably of the same hydrophobic nature.     

Preparation and applications of biofunctionalized,supported lipid bilayers and vesicles

Biofunctional surfaces require advanced design and preparation to match the (bio)recognition ability of biological systems [1]. This requires combined topographic, chemical and visco-elastic surface patterns to match proteins at the nm scale and cells at the micrometer scale. One example of biochemical functionalization, presented here, and which is of both fundamental and application interest, is supported biomimectic (cell)membranes. Specifically we describe preparation and applications of supported phospholipid membranes, which can be made on certain surfaces from unilamellar, 25–200 nm vesicles. On SiO2 at normal pH and with neutral lipids, the vesicles first adsorb intact, and then undergo a phase transformation to a supported bilayer. We have studied the coverage-, vesicle size-, and T-dependence of this process [2], using QCM-D [3], AFM, and SPR. When SiO2 is replaced by TiO2, vesicles adsorb intact. A surface pre-covered with intact vesicles, can be AFM patterned into areas with bilayer, vesicles, and empty surface patches [4]. The results depend critically on AFM tip interaction with vesicle and bilayer, which has been modeled by Monte Carlo simulations [5]. These biomembranes are inert towards protein adsorption [6] and cell attachement [7], which opens up for various applications. Addition of functional molecules, allows sensor functions [8]. Another application is functionalized membranes for surface-specific (stem) cell interactions [9].     

Hydrogenation of fructose on Ru/C catalysts

The hydrogenation of D-fructose on Ru/C catalysts was studied. Under the conditions applied (1 bar H2, 72 degrees C), the furanose forms of D-fructose react, while the pyranose forms do not. However, all anomers adsorb with comparable strength on the surface. The reaction rate is controlled by product inhibition. The selectivity to D-mannitol can be increased from 47 to 63% by promotion of Pd/C and Pt/C catalysts with Sn.     

Polyampholyte Nanoparticles Prepared by Self-Complexation of Cationized Poly(γ-glutamic acid) for Protein Carriers

A novel amphoteric poly(amino acid) is synthesized by grafting a cationic amino acid (L-Arg) to γ-PGA to prepare charged NPs. γ-PGA-Arg NPs can be prepared by the self-complexation of a single polymer by intra-/inter-molecular electrostatic interactions when the polymer is dispersed in water. The size and surface charge of the NPs can be regulated by the grafting degree of Arg (41, 56, and 83%). The smallest NPs are obtained at 56% grafting degree of the γ-PGA-Arg copolymer. The 56 and 83% grafting degree NPs are stable for at least 1 week. Depending on their surface charge, these NPs can selectively adsorb anionically or cationically charged proteins.