Effects of Solution Chemistry on Bacterial Adhesion with Phyllosilicates and Goethite Explained by the Extended DLVO Theory

Adhesion of Bacillus subtilis on kaolinite, montmorillonite, and goethite was investigated over a wide range of ionic strength (IS) and pH using batch experiment. The related surface properties (size, zeta potential, and hydrophobicity) under varying conditions were systematically determined and the interaction energy between the cell and minerals were calculated using the extended Derjaguin, Landau, Verwey, and Overbeek (ExDLVO) theory. Adhesion on kaolinite and montmorillonite increased with IS at low level (< 0.01 mol L^?1 MgCl₂) but declined at high IS level. An increase in IS generally depressed bacterial adhesion on goethite. Elevated pH resulted in decreasing the adhesions on all three minerals. The IS- and pH-effects on adhesion for phyllosilicate systems followed the ExDLVO predictions. For goethite systems, this theory predicted the adhesion trend with IS and that under basic pH, but failed to explain the adhesion at low pH. Such deviation from the theory possibly resulted from chemical interactions between extracellular polymeric substances on cell surface and goethite. These results imply that bacterial adhesions on phyllosilicates are primarily governed by the ExDLVO interactions, and those on iron oxides are mediated by the combination of ExDLVO and non-ExDLVO interactions.     

Adsorption of DNA by Bacteria and Their Composites with Minerals

Previous studies revealed the thermodynamic properties of DNA adsorption on pure minerals or biomasses; however, there has been little attempt to develop such studies on bacteria–mineral composites. Equilibrium adsorption experiments, attenuated total reflectance Fourier transform infrared spectroscopy, and isothermal titration calorimetry were employed to investigate the adsorption of DNA by Bacillus subtilis, Pseudomonas putida, and their composites with minerals. Similar capacity and affinity were observed for DNA adsorption on two bacterial cells. However, different patterns were found in the adsorption of DNA by bacteria–mineral composites. The Gram-positive bacterium B. subtilis enhanced the adsorption of DNA on its mineral composites compared with their individual components, while the composites of Gram-negative bacterial cells with kaolinite and goethite bound lower amounts of DNA than the predicted values. The thermodynamic parameters and the Fourier transform infrared spectra showed that van der Waals force and hydrogen bonding are responsible for the DNA adsorption on B. subtilis–minerals and P. putida–kaolinite. By contrast, the entropy increases of excluded water rearrangement and dehydration effect play key roles in the interaction between DNA and P. putida–montmorillonite/goethite composites.     

Adsorption and anti-ultraviolet light characteristics of the protoxin from Bacillus thuringiensis on montmorillonite,kaolinite, zinc oxide and rectorite

The adsorption, desorption and anti-ultraviolet light characteristics of the protoxin from Bacillus thuringiensis strain WG-001 on montmorillonite, kaolinite, zinc oxide and rectorite were studied. The protoxin was easily adsorbed onto minerals and the adsorption reached equilibrium within 0.5–1.0 h (except for rectorite). The adsorption isotherms of protoxin at different concentrations in sodium carbonate buffer (pH 9) followed the Langmuir (R ² >0.97) and Freundlich (R ² >0.95) equations. The maximum amounts of protoxin adsorbed were in the order: montmorillonite>rectorite>znic oxide>kaolinite. In the range of pH from 9 to 11 (carbonate buffer), the protoxin adsorbed decreased with increasing pH. The adsorption was not significantly affected by the temperature between 5 and 45°C. Both free and adsorbed protoxin were toxic to larvae of Heliothis armigera. The LC₅₀ value of free and adsorbed protoxin on montmorillonite, rectorite, zinc oxide and kaolinite were 14±1.16, 1.76±0.31, 2.94±0.71, 4.78±2.08 and 1.91±0.91 µg mL^?1, respectively. After 1 h of ultraviolet irradiation, the LC₅₀ of the above samples increased by 41.4, 19.3, 16.3, 125.9 and 62.3%, respectively. The desorption of adsorbed protoxin in water ranged from 30.1 to 64.9% and from 18.5 to 48.7% in carbonate buffer.     

Binding of the protoxin and toxin proteins ofBacillus thuringiensis subsp.kurstaki on clay minerals

The equilibrium adsorption and binding of the delta-endotoxin proteins, i.e., the protoxins (M_r=132 kDa) and toxins (M_r=66 kDa), fromBacillus thuringiensis subsp.kurstaki were greater on montmorillonite than on kaolinite (five-fold more protoxin and three-fold more toxin were adsorbed on montmorillonite). Approximately two- to three-fold more toxin than protoxin was adsorbed on these clay minerals. Maximum adsorption occurred within 30 min (the shortest interval measured), and adsorption was not significantly affected by temperatures between 7° and 50°C. The proteins were more easily desorbed from kaolinite than from montmorillonite; they could not be desorbed from montmorillonite with water or 0.2% Na₂CO₃, but they could be removed with Tris-SDS (sodium dodecyl sulfate) buffer. Adsorption was higher at low pH and decreased as the pH increased. Adsorption on kaolinite was also dependent on the ionic nature of the buffers. The molecular mass of the proteins was unaltered after adsorption on montmorillonite, as shown by SDS-PAGE (polyacrylamide gel electrophoresis) of the desorbed proteins; no significant modifications occurred in their structure as the result of binding on the clay, as indicated by infrared analysis; and there was no significant expansion of the clay by the proteins, as shown by x-ray diffraction analysis. The bound proteins appeared to retain their insecticidal activity against the third instar larvae ofTrichoplusia ni.     

Interaction,at Ambient Temperature and 80 °C,between Minerals and Artificial Seawaters Resembling the Present Ocean Composition and that of 4.0 Billion Years Ago

Probably one of the most important roles played by minerals in the origin of life on Earth was to pre-concentrate biomolecules from the prebiotic seas. There are other ways to pre concentrate biomolecules such as wetting/drying cycles and freezing/sublimation. However, adsorption is most important. If the pre-concentration did not occur—because of degradation of the minerals—other roles played by them such as protection against degradation, formation of polymers, or even as primitive cell walls would be seriously compromised. We studied the interaction of two artificial seawaters with kaolinite, bentonite, montmorillonite, goethite, ferrihydrite and quartz. One seawater has a major cation and anion composition similar to that of the oceans of the Earth 4.0 billion years ago (ASW 4.0 Ga). In the other, the major cations and anions are an average of the compositions of the seawaters of today (ASWT). When ASWT, which is rich in Na⁺ and Cl^?, interacted with bentonite and montmorrilonite structural collapse occurred on the 001 plane. However, ASW 4.0 Ga, which is rich in Mg²⁺ and SO₄ ^2?, did not induce this behavior. When ASW 4.0 Ga was reacted with the minerals for 24 h at room temperature and 80 °C, the release of Si and Al to the fluid was below 1 % of the amount in the minerals—meaning that dissolution of the minerals did not occur. In general, minerals adsorbed Mg²⁺ and K⁺ from the ASW 4.0 Ga and these cations could be used for the formation of polymers. Also, when the minerals were mixed with ASW 4.0 Ga at 80 °C and ASWT at room temperature or 80 °C it caused the precipitation of CaSO₄?2H₂O and halite, respectively. Finally, further experiments (adsorption, formation of polymers, protection of molecules against degradation, primitive cell wall formation) performed under the conditions described in this paper will probably be more representative of what happened on the prebiotic Earth.     

Bt毒素在三种矿物表面的吸附与解吸

研究了Bt库斯塔克亚种(kurstaki）毒素（65 kDa）在高岭土、针铁矿和氧化硅表面的吸附和解吸特性.结果表明：在磷酸盐缓冲体系（pH 8）中,3种矿物的等温吸附曲线均符合Langmuir方程（R²>0.9661）,它们对Bt毒素的吸附顺序为：针铁矿﹥高岭土﹥二氧化硅.矿物对Bt毒素的吸附1 h就基本达到了吸附平衡.在pH 6～8范围内,针铁矿、高岭土和二氧化硅对Bt毒素的吸附量随pH值的升高而降低.10 ℃～50 ℃范围内,针铁矿和氧化硅对Bt毒素吸附量随温度升高有所下降（8.39％和47.06％）,高岭土对Bt毒素吸附则略有升高（5.91％）.红外光谱分析显示,Bt毒素被矿物吸附后结构仅有微小变化.被矿物吸附的Bt毒素不易被去离子水解吸,水洗3次总解吸率为28.48%～42.04%.     

Interaction between ATP,metal ions,glycine, and several minerals

Summary The adsorption of ATP and ADP on montmorillonite, kaolinite, and A1(OH)₃ was studied as a funtion of pH and, for montmorillonite and kaolinite, as a funtion of the ionic composition of the system. The three minerals exhibit different adsorption charcteristics. Mg²⁺- and Zn²⁺-montmorillonite adsorb ATP and ADP more than Na⁺-montmorillonite, presumably because of complex formation. In kaolinite, the effect of these divalent cations is small. Pure ATP decomposes upon heating, and the rate of the decomposition is accelerated by the presence of glycine. Drying and heating glycine to 70°C under vacuum in the presence of ATP results in abiotic peptide formation with yields up to 0.25%. This peptide formation also occurs when kaolinite or montmorillonite is added to the system. The presence of kaolinite, Mg²⁺-or Zn²⁺-koalinite, or Mg²⁺-montmorillonite results in a reduction in the rate of the ATP decomposition in the abiotic peptide synthesizing system. These results suggest that one role for clays and metal ions in chemical evolution may have been the stabilization of nucleotides during prebiotic peptide synthesis.On Leave from the Hebrew University of Jerusalem, Israel     

Effect of the clay minerals montmorillonite and kaolinite on the genetic transformation of competentBacillus subtilis cells

The effect of the clay minerals montmorillonite and kaolinite on the transformation of competentBacillus subtilis cells with chromosomal DNA was studied. Clay particles were found to substantially increase the transformation frequency of competent cells, as well as the rate of their spontaneous chromosomal and plasmid transformation. The effect was ascribed to the adsorption of bacterial cells on the surface of mineral particles.     

Adsorption isotherms of lanthanum to soil constituents and effects of pH,EDTA and fulvic acid on adsorption of lanthanum onto goethite and humic acid

Abstract

La³⁺ adsorption isotherms to five soil constituents (quartz, feldspar, kaolinite, goethite and humic acid) are studied. EDTA, fulvic acid and pH effects are also investigated on the adsorption of lanthanum by goethite and humic acid because of their relative importance in affecting metal environmental behavior. Adsorption isotherms of La³⁺ to five constituents show differences in adsorption capacity and in shape in the studied range of La³⁺. These constituents can be classified according to their adsorption capacity: humic acid > goethite ≈ kaolinite > feldspar ≈ quartz. pH increase could promote humic acid and goethite adsorption of La³⁺ while EDTA could reduce the adsorption by these two adsorbents. Fulvic acid can reduce humic acid adsorption but has less effect on adsorption by goethite.     

Sorption and desorption of copper by and from clay minerals

Summary The sorption of Cu by different clay minerals from dilute CuSO₄ solutions was studied as a function of pH. It was found that Cu sorption increased with increasing the equilibrium pH. The low sorption at low pH values was attributed to the competition effect of H⁺ ions and the release of octahedral Mg, Fe and Al from the 2: 1 minerals in acid solutions. The higher sorption of copper at higher pH values was related to the absence of H⁺ ions and to the increase in the pH-dependent negative charge in kaolinite and gibbsite.The desorption of copper using solutions of 1 N NaCl at different pH values indicated that kaolinite and montmorillonite released large amounts of their adsorbed Cu even at high pH values. Vermiculite, on the other hand, exhibited a strong retention of Cu against extraction with NaCl. Oven-drying had no significant effect on the desorption characteristics of the Cu-saturated clays.The Ca-Cu exchange isotherms on montmorillonite were studied at two different pH values. The isotherms indicated a preference of Ca at the lower pH (pH 3.5), with K = 0.931 and G = +41.0 cal./mole. At the higher pH (5.2) the isotherms indicated a preference of Cu with K = 1.282 and G = –141.0 cal./mole. The difference was attributed to the competition of H⁺ at low pH.     

Heterogeneous Catalytic Oxidation of Phenanthrene by Hydrogen Peroxide in Soil Slurry: Kinetics,Mechanism, and Implication

The degradation of phenanthrene sorbed on soil has been carried out using a H₂O₂/goethite heterogeneous catalytic oxidation process. The effect of operating variables, such as the goethite concentration, pH, H₂O₂ concentration, soil organic matter, and bicarbonate ions has been investigated. The reaction followed pseudo-first order kinetics. The rate constants were evaluated and varied between 2.0×10^?4 and 1.1×10^?3?min^?1 depending on the H₂O₂ concentration. The highest rate of degradation of phenanthrene was observed at a H₂O₂ concentration of 5?M and 134.0?g/kg goethite. The intermediate product formed during the degradation of phenanthrene was identified to be salicylic acid that finally degraded to CO₂ and H₂O. H₂O₂ consumption continued as the OH radical attacked the salicylic acid. More than 80% consumption of the 5?M H₂O₂ took place within 30?min, and the degradation was almost complete after 3?h of reaction. Neutral pH was found to be effective in the removal of phenanthrene. Both soil organic matter (SOM) and bicarbonate ions in the soil inhibited the oxidation rate of phenanthrene.     

草酸对土壤胶体与矿物表面酶的吸附及活性影响

采用平衡批处理法,研究了模拟根系分泌物--草酸溶液的浓度、pH对酸性磷酸酶在针铁矿、高岭石及黄棕壤和砖红壤胶体(＜2μm)上的吸附及比活的影响.结果表明,针铁矿对磷酸酶的吸附量受草酸浓度的影响较小,其它供试胶体对蛋白的吸附量随草酸浓度的升高,一般表现为先急剧降低(0～5mmol·L^-1),之后逐渐升高到与对照相当或略低.这与草酸在土壤胶体和矿物表面的配位形态及其对载体表面的电荷改变、溶解有关.草酸体系中,供试胶体对磷酸酶的吸附顺序为针铁矿>黄棕壤＞高岭石＞砖红壤.酶在草酸体系中的最大吸附点位一般出现在蛋白的等电点(IEP)和供试胶体的PZC之间,而酶在草酸体系中被固定到供试胶体上之后,其最适比活点随胶体类型的不同而没有变化或有所高移.     

Michaelis constant (K m ) of acid phospatase as affected by montmorillonite,illite, and kaolinite clay minerals

The influence of Ca homoionic clay minerals (montmorillonite, illite, and kaolinite) on the activity,K _m , andV _m values of acid phosphatase was examined in model experiments. At each substrate (p-nitrophenyl phosphate) level tested, the addition of increasing amounts of clays (50, 100, and 150 mg, respectively) decreased the activity and increased theK _m value from 1.43×10^–3 m PNP (in the soluble state) to 82.3×10^–3M (montmorillonite), 8.02×10^–3 m (kaolinite), and 7.65×10^–3 m (illite) at the 150 mg level. The maximum enzyme reaction velocity (V _m ) remained nearly constant at different amounts of kaolinite and illite, but increased remarkably with rising quantities of montmorillonite. Apparently, the substrate affinity of sorbed acid phosphatase is significantly lower with montmorillonite than with kaolinite or illite. This may be ascribed to an intensive sorption of both substrate and enzyme to the surface as well as to interlattice sites of montmorillonite.     

Desorption and plant-availability of phosphate sorbed by some important minerals

Experiments were conducted to study the desorption characteristics and plant-availability of phosphate sorbed by some important variable-charge minerals including kaolinite, goethite and amorphous Al oxide. Phosphate desorption from the complexes of goethite-P, kaolinite-P and Al oxide-P by equilibration with 0.02M KCl, resin or some commonly used chemical extractants was slow compared to desorption from a permanent-charge mineral (montmorillonite). However, rice plants were not observed under P deficiency in a pot trial with a phosphate-mineral complex as the only P source for both the permanent-charge mineral and the variable-charge minerals at either 50% or 100% sorption saturation with the exception of goethite-P at 50% saturation. In the exceptional goethite-P treatment, plant P concentration (1.0 g kg^–1) was on the threshold of P deficiency. From 15% to 31% of the applied P was recovered by the plants within a growing period of three months, depending on sorption saturation and mineral type. Both the dry matter yield and P uptake decreased with decreasing sorption saturation for all the tested complexes except for Al oxide-P₁₀₀ (100% saturation). In the case of Al oxide-P₁₀₀, Al toxicity may have occurred, for poor root growth and high Al concentration in the plants were observed. The effect of sorption saturation on the yield and P uptake of plant was obvious for kaolinite and goethite but not very significant for montmorillonite. Based on the recovery of applied P, the plant-availability decreased in the following order: kaolinite-P₁₀₀ > goethite-P₁₀₀ > Al oxide-P₅₀ > montmorillonite-P₁₀₀ > montmorillonite-P₅₀ > kaolinite-P₅₀ > goethite-P₅₀. Fractionation of the sorbed P before and after plant uptake showed that most of the P uptake originated from the resin-exchangeable P fraction in montmorillonite-P complex, but came mainly from NaOH-extractable fractions in goethite-P complex, whereas all the resin-P, NaHCO₃-P and NaOH-P fractions in kaolinite- and amorphous Al oxide-P complex made a contribution to P uptake.     

TCNE-modified graphene as an adsorbent for N<Subscript>2</Subscript>O molecule: a DFT study

Adsorption behavior of nitrous oxide (N₂O) on pristine graphene (PG) and tetracyanoethylene (TCNE) modified PG surfaces is investigated using density functional theory. A number of initial adsorbate geometries are considered on both surfaces and the most stable ones are chosen upon calculation of the adsorption energies (E_ads). N₂O is found to adsorb in a weakly exoergic process (E_ads?～??3.18 kJ mol^?1) at the equilibrium distance of 3.52 Å on the PG surface. N₂O adsorption can be greatly enhanced with the presence of a TCNE molecule (E_ads?=??87.00 kJ mol^?1). Mulliken charge analysis confirms that adsorption of N₂O is not accompanied by distinct charge transfer from the surfaces to the molecule (? 0.001 │e│ for each case). Moreover, on the basis of calculated changes in the HOMO/LUMO energy gap, it is found that electronic properties of PG and TCNE modified PG are not sensitive toward adsorption of N₂O, indicating that both surfaces are not good enough to introduce as an N₂O detector. However, the considerable amount of E_ads in TCNE modified PG can be a guide to the design of graphene-based adsorbents for N₂O capture.     

Studies on Plant Viruses-soil Colloids Interactions

Stability and infectivity of cucumber mosaic virus, strain D (CMV-D), associations with kaolinite and montmorillonite were determined, as affected by: i) nature of clay minerals; ii) nature of clay saturating cations; iii) exposure to dissociating salt solutions (2 M LiCl). Infectivity experiments carried out with sediments following centrifugation of the virus-clay mixtures (sd fractions), showed that, in absence of LiCl, the highest values were obtained with kaolinite, in the order Li⁺= K⁺ > NH₄⁺= Mg⁺⁺ > Na⁺ > Ca⁺⁺ clay saturating cations, ranging between 91 and 30 % of the untreated control, whereas comparable montmorillonite fractions gave infectivity values with all cations about 10–15 % of the control. In presence of 2 M LiCl, montmorillonite preserved infectivity of the same fraction (Lsd fraction), which, in the case of Li⁺- or Ca⁺⁺ -saturated samples, was higher when compared with the corresponding sd values, thus revealing for these cations an amplifying effect on infection. This did not occur with kaolinite which, however, gave a Lsd fraction more infectious than the other clay. The results confirmed that clay minerals preserve infectivity of virus preparations exposed to critical conditions, thus providing an explanation for the persistence in soil of infectivity of viruses which are normally not soil-borne. Under appropriate soil conditions these viruses may form complexes with clay minerals thus retaining an infectivity which may be enhanced by addition of cations as those contained in fertilizers.     

Immobilization of oxyreductases on inorganic supports based on alumina. Immobilization of lactate dehydrogenase on alumina by adsorption

Lactate dehydrogenase (LDH) was adsorbed on low-(γ, η) and high -(θ, α) temperature forms of alumina. θ-Al₂O₃ exhibited the greatest adsorption ability. The maximum adsorption value was 30 mg LDH/g of a carrier. The conditions for irreversible adsorption have been determined. An adsorption isotherm on θ-Al₂O₃ for pH 6.0 has been obtained; the LDH_ads surface area and the carrier surface portion accessible to the enzyme molecules have been calculated. The reaction kinetic parameter were determined by taking into account the reaction proceeding in the intradiffusional region. The specific catalytic activity (A_spec) of LDH_ads at small surface coverage of θ-Al₂O₃ is five times less than A_spec of the native enzyme and K_M^imm with respect to NADH exceeds K_M^nat by two orders or magnitude. The is evidence for a strong LDH–Al₂O₃ interaction and a considerable deformation of the enzyme globule. A_spec and K_M decrease as the amount of the enzyme attached to the carrier increases. Due to adsorption. LDH becomes thermostable and durable. The LDH_ads samples conserve 20–40% of their activity at room temperature during a year.     

Influence of clay minerals on sorption of bacteriolytic enzymes

Myxobacteria presumably produce extracellular bacteriolytic enzymes when they are growing in soil. In order to study their ecological significance, adsorption experiments were performed with lytic enzymes produced byMyxococcus virescens in casitone media. Different soils as well as montmorillonite and kaolinite can rapidly adsorb the bacteriolytic but not the proteolytic enzymes. About 1 gm of montmorillonite per liter of cell-free culture solution is enough for the adsorption of 97% of the bacteriolytic enzymes. The adsorption per unit weight is about 100 times greater on montmorillonite than on kaolinite. About 40% of the adsorbed enzymes can be eluted with solutions of high pH or high ionic strength. The only desorbed bacteriolytic enzyme is the alanyl-∈-N-lysine endopeptidase.     

Studies of lysozyme binding to histamine as a ligand for hydrophobic charge induction chromatography

Histamine was immobilized on Sepharose CL‐6B (Sepharose) for use as a ligand of hydrophobic charge induction chromatography (HCIC) of proteins. Lysozyme adsorption onto Histamine‐Sepharose (HA‐S) was studied by adsorption equilibrium and calorimetry to uncover the thermodynamic mechanism of the protein binding. In both the experiments, the influence of salt (ammonium sulfate and sodium sulfate) was examined. Adsorption isotherms showed that HA‐S exhibited a high salt tolerance in lysozyme adsorption. This property was well explained by the combined contributions of hydrophobic interaction and aromatic stacking. The isotherms were well fitted to the Langmuir equation, and the equilibrium parameters for lysozyme adsorption were obtained. In addition, thermodynamic parameters (ΔH_ads, ΔS_ads, and ΔG_ads) for the adsorption were obtained by isothermal titration calorimetry by titrating lysozyme solutions into the adsorbent suspension. Furthermore, free histamine was titrated into lysozyme solution in the same salt‐buffers. Compared with the binding of lysozyme to free histamine, lysozyme adsorption onto HA‐S was characterized by a less favorable ΔG_ads and an unfavorable ΔS_ads because histamine was covalently attached to Sepharose via a three‐carbon‐chain spacer. Consequently, the immobilized histamine could only associate with the residues on the protein surface rather than those in the hydrophobic pocket, causing a less favorable orientation between histamine and lysozyme. Further comparison of thermodynamic parameters indicated that the unfavorable ΔS_ads was offset by a favorable ΔH_ads, thus exhibiting typical enthalpy‐entropy compensation. Moreover, thermodynamic analyses indicated the importance of the dehydration of lysozyme molecule and HA‐S during the adsorption and a substantial conformational change of the protein during adsorption. The results have provided clear insights into the adsorption mechanisms of lysozyme onto the new HCIC material. © 2009 American Institute of Chemical Engineers Biotechnol. Prog., 2010     

Entrapping Molecules in Zeolites Nanocavities: A Thermodynamic and Ab-Initio Study

Adsorption enthalpies of Ar, N₂, CO, H₂O, CH₃CN and NH₃ on H-BEA and H-MFI zeolites and on Silicalite, have been measured calorimetrically at 303K in order to assess the energetic features of dispersive forces interactions (confinement effects), H-bonding interactions with surface silanols and specific interactions with Lewis and Brønsted acidic sites. The adsorption of the molecular probes with model clusters mimicking surface silanols, Lewis and Bronsted sites has been simulated at ab-initio level. The combined use of the two different approaches allowed to discriminate among the different processes contributing to the measured (-Δ_adsH). Whereas CO and N₂ single out contributions from Lewis and Br{\o}nsted acidic sites, Ar is only sensitive to confinement effects. For H₂O, CH₃CN and NH₃ the adsorption on Brønsted sites is competitive with the adsorption on Lewis sites. The energy of interaction of H₂O with all considered zeolites is surprisingly higher than expected on the basis of -Δ_adsH vs PA correlation.