Abstract  Sorbents for high temperature CO2 capture are under intensive development owing to their potential applications in advanced zero emission power, sorption-enhanced steam methane reforming for hydrogen production and energy storage systems in chemical heat pumps. One of the challenges in the development is the prevention of sintering of the sorbent (normally a calcium oxide derivative) which causes the CO2 capture capacity of the material to deteriorate rapidly after a few cycles of utilization. Here we show that a simple wet mixing method can produce sintering-resistant sorbents from calcium and magnesium salts of d-gluconic acid. It was found that calcium oxide was well distributed in the sorbents with metal oxide nanoparticles on the surface acting as physical barriers, and the CO2 capture capacity of the sorbents was largely maintained over multiple cycles of utilization. This method was also applied to other organometallic salts of calcium and magnesium/aluminum and the produced sorbents showed similarly high reversibility.

Abstract  AIMS: The purpose of this work was to study the involvement of micro-organisms, which develop together with Botrytis cinerea on grapes, in the SO2 binding power of musts.

METHODS AND RESULTS: Yeasts and bacteria were involved. Most bacteria were acetic acid bacteria, mainly of the Gluconobacter genus. Unlike oxidative yeasts, Gluconobacter produce gluconic acid (in balance with delta-gluconolactone) from glucose, 5-oxofructose from fructose and dihydroxyacetone from glycerol. Production of carbonyl compounds from other sugars and polyols was not detected or was very weak.

CONCLUSION: Acetic acid bacteria are responsible for the increases in SO2 binding power of musts from botrytized grapes by oxidizing the three main sugars of these grapes.

SIGNIFICANCE AND IMPACT OF THE STUDY: Up to 80% of the SO2 binds with products of Gluconobacter which easily grow on 'botrytized' grapes. Depending on climatic conditions, some vintages are particularly difficult to stabilize.

Abstract  BACKGROUND: Patients' exposure to and potential toxicity from aluminum in parenteral nutrition (PN) formulations is an important concern of healthcare providers.

OBJECTIVE: To determine the potential for aluminum toxicity caused by PN in hospitalized adults who have risk factors of both acute kidney injury and PN.

METHODS: Adults who required PN and had a serum creatinine (SCr) level at least 1.5 times greater than the admission SCr on the first day of PN were studied in a retrospective fashion. Protein was administered based on whether hemodialysis was being used (0.6-1 g/kg/day without hemodialysis; 1.2-1.5 g/kg/day with hemodialysis). Aluminum exposure was determined for each patient by multiplying the volume of each PN component by its concentration of aluminum. Unpaired t-tests, Fisher's exact test, and analysis of variance were used for statistical analysis. Data are presented as mean +/- SD.

RESULTS: Thirty-six patients (aged 50.4 +/- 20.4 y; weight 90.2 +/- 32.8 kg) were studied. Initial serum urea nitrogen and SCr were 47 +/- 23 and 3.3 +/- 1.4 mg/dL, respectively. Twelve patients received hemodialysis. The mean aluminum exposure was 3.8 +/- 2 microg/kg/day in the 36 patients. Of these, 29 had safe calculated aluminum exposure (<5 microg/kg/day) and 7 had high calculated aluminum exposure (>5 microg/kg/day). Patients with safe aluminum exposure had significantly higher SCr levels than did those with high aluminum exposure (3.5 +/- 1.5 vs 2.2 +/- 0.7 mg/dL; p < 0.04). Patients with high aluminum exposure received significantly more aluminum from calcium gluconate compared with those who had safe aluminum exposure (357 +/- 182 vs 250 +/- 56 microg/day; p < 0.02). Limitations of the study include its retrospective design, which resulted in calculated versus direct measurement of aluminum.

CONCLUSIONS: Using our calculations, we believe that most patients with acute kidney injury who require PN do not receive excessive exposure to aluminum from the PN formulation, despite having 2 risk factors (acute kidney injury, PN) for aluminum toxicity.

Abstract  AIMS: To study phosphate solubilization in Penicillium purpurogenum as function of medium pH, and carbon and nitrogen concentrations.

METHODS AND RESULTS: Tricalcium phosphate (CP) solubilization efficiency of P. purpurogenum was evaluated at acid or alkaline pH using different C and N sources. Glucose- and (NH(4) )(2) SO(4) -based media showed the highest P solubilization values followed by fructose. P. purpurogenum solubilizing ability was higher in cultures grown at pH 6·5 than cultures at pH 8·5. Organic acids were detected in both alkaline and neutral media, but the relative percentages of each organic acid differed. Highest P release coincided with the highest organic acids production peak, especially gluconic acid. When P. purpurogenum grew in alkaline media, the nature and concentration of organic acids changed at different N and C concentrations. A factorial categorical experimental design showed that the highest P-solubilizing activity, coinciding with the highest organic acid production, corresponded to the highest C concentration and lowest N concentration.

CONCLUSIONS: The results described in the present study show that medium pH and carbon and nitrogen concentrations modulate the P solubilization efficiency of P. purpurogenum through the production of organic acids and particularly that of gluconic acid. In the P solubilization optimization studies, glucose and (NH(4) )(2) SO(4) as C and N sources allowed a higher solubilization efficiency at high pH.

SIGNIFICANCE AND IMPACT OF THE STUDY: This organism is a potentially proficient soil inoculant, especially in P-poor alkaline soils where other P solubilizers fail to release soluble P. Further work is necessary to elucidate whether these results can be extrapolated to natural soil ecosystems, where different pH values are present. Penicillium purpurogenum could be used to develop a bioprocess for the manufacture of phosphatic fertilizer with phosphate calcium minerals.

Abstract  The aim of this work was to characterize and to quantify ozonation by-products of glucose in ultrapure water ([Glucose](o) = 5 mmol 1(-1); initial pH : pH approximate to 6, final pH : approximate to 3). HPLC and GC analyses showed that ozonation of glucose yields mainly gluconic acid (0.6 - 0.7 mole I mole of glucose eliminated) and formic acid (0.2 - 0.25 mole / mole of glucose eliminated) at the beginning of the reaction. Glycolic acid, formaldehyde and peroxides were also formed for low ozone dosages. GC/MS analyses carried out on extracts from ozonated solutions of glucose and gluconic acid (90-95% removal of the initial organic compound) allowed the identification of several by-products wih six carbon atoms (hexosuloses, glucuronic and glucaric acids) and with less carbon atoms (acids and aldehydes).

Abstract  The anodic behaviour of Al in gluconic acid (HG) solutions was studied. Al was found to pit in such solutions. Surface and cross-sectional views of the SEM images recorded beyond the breakdown potential (E(b)) revealed the occurrence of intense pitting attack with the formation of large hemispherical pits. The effect of adding some environmentally acceptable inorganic inhibitors (tungstates, molybdates or silicates) on the pitting corrosion behaviour of Al in HG solutions was also studied. Measurements were carried out under the influence of various experimental variables based on polarization and chronoamperometric techniques. These measurements were complemented by ex situ scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) examinations of the electrode surface. The presence of these compounds in HG solutions decreased the passive current density (j(pass)) and increased Eb. In HG solutions, chronoamperometric measurements showed that the anodic current density first decreased, due to growth of a passive oxide film, then increased withme after a pit incubation time, t(i) and finally attained a steady-state value. Value of t(i) was shortened and simultaneously the steady-state current was elevated, corresponding to an increase in the rate of pit initiation and growth, with increasing applied anodic potential and HG concentration. The rate of pit nucleation (t(i)(-1)) was found to decrease to an extent depending on the type and concentration of the introduced inhibitor. The inhibitory effect of these compounds decreased in the order: Si(2)O(5)(2-) > WO(4)(2-) > WO(4)(2-) > MoO(4)(2-). (C) 2010 Elsevier Ltd. All rights reserved.

Abstract  In this study, an attempt was made to identify an effective phosphate solubilizing bacteria from pesticide polluted field soil. Based on the formation of solubilization halo on Pikovskaya's agar, six isolates were selected and screened for pesticide tolerance and phosphate (P) solubilization ability through liquid assay. The results showed that only one strain (SGRAJ09) obtained from Achillea clavennae was found to tolerate maximum level of the pesticides tested and it was phylogenetically identified as Pseudomonas sp. It possessed a wide range of pesticide tolerance, ranging from 117 μg mL(-1) for alphamethrin to 2,600 μg mL(-1) for endosulfan. The available P concentrations increased with the maximum and double the maximum dose of monocrotophos and imidacloprid, respectively. On subjected to FT-IR and HPLC analysis, the presence of organic acids functional group in the culture broth and the production of gluconic acid as dominant acid aiding the P solubilization were identified. On comparison with control broth, monocrotophos and imidacloprid added culture broth showed quantitatively high organic acids production. In addition to gluconic acid production, citric and acetic acids were also observed in the pesticide amended broth. Furthermore, the Pseudomonas sp. strain SGRAJ09 possessed all the plant growth promoting traits tested. In presence of monocrotophos and imidacloprid, its plant growth promoting activities were lower than that of the pesticides unamended treatment.

Abstract  HEEP COPYRIGHT: BIOL ABS. NOTE HUMAN CALCIUM GLUCONATE ALUMINUM SALTS CALCIUM EDTA SERPENTINE BORON IRON METABOLIC-DRUG ANTIDOTE OSTEO POROSIS

Abstract  The present work consisted in the study of the oxidation Yield induced by catalysts during ozonation of sodium gluconate, toluene sulfonic acid and Triton X100 in dilute aqueous solution (TOC = 8 mg C/L). Two operating conditions have been used to demonstrate the enhancement brought about by catalytic ozonation: continuous filtration experiments and batch tests.

Dynamic filtration experiments have been performed on catalysts previously saturated to simulate the behavior of the catalyst over a long period of use.

Batch experiments which allowed us to distinguish the part due to adsorption, ozonation and catalytic effect were carried out on three catalysts with intent to test their efficiency. (C) 1998 Published by Elsevier Science Ltd. All rights reserved.

Abstract  BIOSIS COPYRIGHT: BIOL ABS. A multinational interlaboratory study to investigate the bovine corneal opacity and permeability (BCOP) assay is presented. The aim of this work was to determine the capability and possible limitations of this method to predict ocular irritancy of a large set of chemicals. The assays were carried out in 12 European laboratories with different types of activity. In each of these laboratories 52 substances, with a wide range of structure, physical form and irritant properties, were tested and in vitro scores were compared with those obtained from concurrent rabbit eye (Draize) tests. The technique was easily learned by workers in the participating laboratories, as shown by the fact that there were consistent responses between treated corneas within an individual laboratory. Interlaboratory variability was also very good. It was found that a given laboratory had a 96% chance of classifying irritants or non-irritants similarly to the other laboratories. In addition, it was

Abstract  BIOSIS COPYRIGHT: BIOL ABS. Aluminum (Al), one of the most widespread element on earth, often contaminates preparations such as parenteral nutrition solutions. Small-volume additives such as calcium gluconate and phosphate salts solutions are the most contaminated. Large-volume parental source solutions such as dextrose, crystalline amino acids and lipid emulsions are significantly less contaminated. Premature infants generally need intravenous feeding and are therefore vulnerable to aluminum toxicity: protective gastrointestinal mechanisms are bypassed and renal function is immature. Several studies showed that Al blood levels and urinary excretion increase when premature infants received parenteral nutrition. Urinary elimination is not adequate and Al accumulation is observed in tissues, especially in bones. Recently, in preterm infants, prolonged intravenous feeding with solutions containing Al was demonstrated to be associated with impaired neurologic development. Montreuil Hospital intensive c

Abstract  Lactobionic acid, [4-beta-(galactosido)-D-gluconic acid] = LBA, is the major component of the Wisconsin organ transplantation preservant fluid and may suppress oxygen radical-induced tissue damage upon reperfusion by the control of FeII autoxidation. FeII and FeIII complexes of LBA and the related gluconic acid (GLC) have been studied herein by titrimetric, infrared, and electrochemical methods (CV; DPP). FeII(GLC) forms quickly at pH 7, but FeII(LBA) reacts in two steps, the second requiring 4 hr. The initial complex lacks coordination of the LBA carboxylate (C-1) and is bound by the "2,3,5" hydroxyl groups. The slow rearrangement forms a "1,2,3,6" chelate which FeII(LBA) shares in common with the donor set of the FeIII(LBA) complex. Titration data shows the removal of three protons from LBA through pH 5 and an additional proton from pH 6 to 9 which is indicative of the [FeIII(LBA)(OH)(H2O)]- formulation with LBA donating at the "1,2,3,6" positions. The more stable, second form of FeII(LBA) has been investigated in its oxidation mechanisms with H2O2 and O2 using selected trapping agents for HO. and ferryl intermediates. Eighty-six percent of the oxidation events of FeII(LBA)/H2O2 occurs in steps involving formation and reduction of freely diffusible HO.. These pathways are altered by the known HO. traps t-butanol, dmso, ethanol, and methanol in the manner predictable for beta-oxidizing radicals (from t-butanol or dmso) and alpha-reducing radicals (from ethanol and methanol). Fourteen percent of the FeII(LBA)/H2O2 reaction occurs via FeIVO intermediates not trapped by t-butanol or dmso, but intercepted by primary and secondary alcohols. The HO. generating pathways are responsible for a competitive LBA ligand oxidation at the C-2 position via HO., formed from FeII(LBA) and H2O2 within the original reaction cage. Competitive ligand oxidation at C-2 is absent for the FeII(LBA)/O2 autoxidation, indicative of a different redox mechanism. The FeII(LBA)/O2 reaction rate is first-order in each component and is insensitive to the presence of t-butanol as an HO. trap. These observations support a ferryl intermediate in the autoxidation pathway and the absence of HO. or free H2O2 during autoxidation. Although chelation of FeII by hard ligand donors such as edta4-, Cl-, or HPO4(2-) accelerate the rate of autoxidation of FeII, chelation of carboxylate, alkoxy, and hydroxyl donors of LBA does not accelerate autoxidation. The implications of these findings, and the absence of an inner-sphere coordination role of the 4-beta-(galactosido) functionality toward the action of LBA in organ preservant fluids, are discussed.

Abstract  About twenty years ago, the cofactor pyrroloquinoline quinone, PQQ, was discovered. Here the author gives his personal view on the reasons why this cofactor was so lately discovered and how the steps in its identification were made. The discovery not only led to subsequent studies on the physiological significance of PQQ but also initiated investigations on other enzymes where the presence of PQQ was expected, resulting in the discovery of three other quinone cofactors, TPQ, TTQ, and LTQ, which differ from PQQ as they are part of the protein chain of the enzyme to which they belong. Enzymes using quinone cofactors, the so-called quinoproteins, copper-quinoproteins, and quinohemoproteins, are mainly involved in the direct oxidation of alcohols, sugars, and amines. Some of the PQQ-containing ones participate in incomplete bacterial oxidation processes like the conversion of ethanol into vinegar and of D-glucose into (5-keto)gluconic acid. Soluble glucose dehydrogenase is the sensor in diagnostic test strips used for glucose determination in blood samples of diabetic patients. Quinohemoprotein alcohol dehydrogenases have an enantiospecificity suited for the kinetic resolution of racemic alcohols to their enantiomerically pure form, certain enantiomers being interesting candidates as building block for synthesis of high-value-added chemicals. Making up for balance after twenty years of quinoprotein research, the following conclusions can be drawn: since quinoproteins do not catalyze unique reactions, we know now that there are more enzymes which catalyze one and the same reaction than we did before, but do not understand the reason for this (compare e.g. NAD/NADP-dependent glucose dehydrogenases, flavoprotein glucose oxidase/dehydrogenase, and soluble/membrane-bound, PQQ-containing glucose dehydrogenases, enzymes all catalyzing the oxidation of beta-D-glucose to delta-gluconolactone but being quite different from each other); however, taking a pragmatic point of view, the foregoing can also be regarded as a positive development since as illustrated by the examples given above, the enlargement of the catalytic arsenal with quinoprotein enzymes provides in more possibilities for enzyme applications; the hopes that PQQ could be a new vitamin have diminished strongly after it has become clear that its occurrance is restricted to bacteria; the impact factor is broader than just the development of the field of quinoproteins, since together with that of enzymes containing a one-electron oxidized amino acid residue as cofactor, it has emphasized that cofactors not only derive from nucleotides (e.g. FAD, NAD) but also from amino acids. Finally, strong indications exist to assume that this is not the end of the story since other quinone cofactors seem awaiting their discovery.

Abstract  Biomasses of methylotrophic bacteria, yielded by biotechnological processes as waste products, can represent a source of ubiquinones, especially of the ubiquinone-10. Possibilities for the separation of ubiquinones were studied on waste biomasses from the microbial production of gluconic acid, from the production of intracellular poly-beta-hydroxybutyric acid (PHB) and from the sewage treatment. The ubiquinones are extracted with supercritical CO2 in the presence of methanol or ethanol as entrainer. The separation of ubiquinones with supercritical extraction was more effective than with conventional extraction methods. The advantages are especially the low extract quantities and the high ubiquinone content in the extracts. The crude ubiquinones can be purified by using the preparative HPLC technique.

Abstract  The production of citric and gluconic acids from fig by Aspergillus niger ATCC 10577 in solid-state fermentation was investigated. The maximal citric and gluconic acids concentration (64 and 490 g/kg dry figs, respectively), citric acid yield (8%), and gluconic acid yield (63%) were obtained at a moisture level of 75%, initial pH 7.0, temperature 30 degrees C, and fermentation time in 15 days. However, the highest biomass dry weight (40 g/kg wet substrate) and sugar utilization (90%) were obtained in cultures grown at 35 degrees C. The addition of 6% (w/w) methanol into substrate increased the concentration of citric and gluconic acid from 64 and 490 to 96 and 685 g/kg dry fig, respectively.

Abstract  In glucose minimal medium a PTS- strain of Escherichia coli [delta (ptsH ptsI crr)] could grow slowly (doubling time, d = 10 h). When the population reached 5 x 10(6) to 2 x 10(7) cells ml-1, mutants growing rapidly (d = 1.5 h) appeared and rapidly outgrew the initial population. These mutants (EF mutants) do not use a constitutive galactose permease for glucose translocation. They synthesize sufficient pyrroloquinoline quinone (PQQ) to yield a specific activity of glucose dehydrogenase (GDH) equivalent to that found in the parent strain grown in glucose minimal medium supplemented with 1 nM-PQQ. Membrane preparations containing an active GDH oxidized glucose to gluconic acid, which was also present in the culture supernatant of EF strains in glucose minimal medium. Glucose utilization is the only phenotypic trait distinguishing EF mutants from the parent strain. Glucose utilization by EF mutants was strictly aerobic as expected from a PQQ-dependent catabolism. The regulation of PQQ production by E. coli is discussed.

Abstract  A new family of activated glycosidic compounds has been designed and synthesized: (2,3,4,6-tetra-O-acetyl-β-D-glucopyranosyl)-2-nitrophenylmethane (1). It is stable in conditions commonly used for synthesis, and it can be converted to a sugar lactone derivative merely by photoirradiation (λ=365 nm): 2,3,4,6-tetra-O-acetyl-D-glucono-1,5-lactone (2). A mechanism for the reaction is proposed. The photochemical conversion of 1 in the presence of methanol has also been demonstrated, giving rise to methyl 2,3,4,6-tetra-O-acetyl-D-gluconate (3).

Abstract  75As NMR (Nuclear Magnetic Resonance) was used as a probe of arsenate interactions in solution. The linewidth at half-height of the 75As NMR signal of arsenate was studied as a function of solution pH and temperature. Below pH 11.5, the 75As signal was too broad to be detected, but at higher pH, up to pH = 13.5, the signal became much narrower. This indicates that the arsenate species AsO4(3-) is quite symmetric, but the asymmetry of HAsO4(2-) is sufficient to cause extensive quadrupolar relaxation of the 75As nucleus. A full pH range 75As and proton NMR study of the interaction of arsenate with ethanol, ethylene glycol, glycerol, ribose, mannose, glucose, gluconic acid and acetate was undertaken in order to follow arsenate ester formation. The 75As line broadening effects and the proton ligand shifts observed indicate that complexation of arsenate by ribose, mannose, glucose, ethanol, ethylene glycol, and glycerol occurs at pH 12.7. However, no significant interaction is detected by NMR with gluconic acid or acetate. The effect of the nucleoside adenosine is quite small and those of phosphate and of the nucleotides AMP and ADP are negligible. The interaction of arsenate with potential cationic centers, such as the basic amino acids lysine and arginine and some macrocyclic triamines, was also studied. Such interaction depends on the pKa for protonation of the amine groups.

Abstract  PESTAB Therapy of chronic poisonings with organochlorine compounds, such as DDT, BHC, 2-KF, dichloralurea, 2,4-D, polychloropinene, and hexachlorobutadiene, is reviewed. Since the mechanism of action of organochlorine compounds in humans is not known, specific antidote therapy is not available. Glucose, calcium gluconate, and vitamins, especially vitamin B, are useful during the initial stage of the chronic poisoning, characterized by autonomic dystonia and the asthenic syndrome. Belladonna preparations are used for elimination of autonomic irritability and of vasculay spasms, and tranquilizers are given to reduce emotional lability. Vitamin preparations, cocarboxylase, adenosine triphosphatase, and oxygen therapy are used to control hypoxia and to increase tonus. Electrophoresis according to Shcherbak with calcium chloride, vitamin B1, dimedrol, or novocaine is also useful. Vitamin B12 is given to control toxic polyneuritis. Hemorrhagic vasculitis is treated with vitamins C and P. B vitamins, thiamine, riboflavin, glucose, and insulin are used for the therapy of toxic hepatitis. Impairments of gastric secretory function are corrected by specific diets, nicotinic acid, and pyridoxine. Vitamins C and B, thiamine, folic acid, and iron preparations are useful in anemia.

Abstract  Ion channels from the midgut apical membrane of gypsy moth (Lymantria dispar) larvae were studied following mechanical fusion of brush-border membrane vesicles with planar phospholipid bilayer membranes. In symmetrical 300 mmol l(-)(1) KCl (pH 9.0), nine different channels with conductances ranging from 27 to 795 pS and linear current/voltage relationships were resolved. In the presence of a KCl gradient across the bilayer (450 mmol l(-)(1 )cis/150 mmol l(-)(1 )trans), 11 different conductance levels ranging from 16 to 850 pS were detected. The channels were slightly cationic: the zero-current reversal potential was shifted by -5 mV to -21 mV compared with symmetrical KCl conditions, corresponding to p(K)/p(Cl) permeability ratios of 1.5-8.0. Most channels were neither voltage-dependent nor Ca(2+)-sensitive and displayed complex gating kinetics. Addition of Ba(2+) or Cs(+) to both sides of the bilayer had little effect on channel activity, but fewer distinct channels were observed when KCl was replaced by potassium gluconate, suggesting an effect of Cl(-) on channel activity. A reduced number of channels was also detected when KCl was replaced by N-methyl- d-glucamine-HCl. Under asymmetrical N-methyl-d-glucamine-HCl conditions, only anionic channels were observed. They exhibited current rectification (35 pS at negative voltages and 81 pS at positive voltages) and were strongly voltage-dependent.

Abstract  Membrane-integrated quinoprotein glucose dehydrogenase from Acinetobacter calcoaceticus was produced by heterologous expression of the gene for it in an Escherichia coli recombinant strain. The apoenzyme (lacking the cofactor pyrroloquinoline quinone, PQQ) was solubilized with Triton X-100 and purified to homogeneity. Reconstitution of the apoenzyme to full activity in the assay was achieved with a stoichiometric amount of PQQ in the presence of Mg2+. Just as for other PQQ-containing dehydrogenases where Ca2+ fulfills this role, Mg2+ anchors PQQ to the mGDH protein and activates the bound cofactor. This occurs in a precise way since high anomer specificity was found for the enzyme toward the sugars tested. Although the steady-state-type kinetics were as expected for a dye-linked dehydrogenase (ping-pong) and the PQQ in it was present in oxidized form, addition of glucose to the holoenzyme resulted in a very slow but continuous production of gluconolactone; i.e., the reaction did not stop after one turnover, with O2 apparently acting as an (albeit poor) electron acceptor by reoxidizing PQQH2 in the enzyme. The surprisingly low reactivity with glucose, in the absence of dye, as compared to the activity observed in the steady-state assay appeared to be due to formation of an anomalous enzyme form, mGDH. Formation of normal holoenzyme, mGDH, reducing added glucose immediately to gluconolactone (in one turnover), was achieved by treating mGDH with sulfite, by reconstituting apoenzyme with PQQ in the presence of sulfite, or by applying assay conditions to mGDH (addition of PMS/DCPIP). As compared to other quinoprotein dehydrogenases, mGDH appears to be unique with respect to the mode of PQQ-binding, as expressed by the special conditions for reconstitution and the absorption spectra of the bound cofactor, and the reactivity of the reduced enzyme toward O2. The primary cause for this seems not to be related to a different preference for the activating bivalent metal ion but to the special way of binding of PQQ to mGDH.

Abstract  The mineral phosphate-solubilizing (MPS) activity of a Pantoea agglomerans strain, namely MMB051, isolated from an iron-rich, acidic soil near Ciudad Piar (Bolívar State, Venezuela), was characterized on a chemically defined medium (NBRIP). Various insoluble inorganic phosphates, including tri-calcium phosphate [Ca(3)(PO(4))(2)], iron phosphate (FePO(4)), aluminum phosphate (AlPO(4)), and Rock Phosphate (RP) were tested as sole sources of P for bacterial growth. Solubilization of Ca(3)(PO(4))(2) was very efficient and depended on acidification of the external milieu when MMB051 cells were grown in the presence of glucose. This was also the case when RP was used as the sole P source. On the other hand, the solubilization efficiency toward more insoluble mineral phosphates (FePO(4) and AlPO(4)) was shown to be very low. Even though gluconic acid (GA) was detected on culture supernatants of strain MMB051, a consequence of the direct oxidation pathway of glucose, inorganic-P solubilization seemed also to be related to other processes dependent on active cell growth. Among these, proton release by ammonium (NH(4)(+) ) fixation appeared to be of paramount importance to explain inorganic-P solubilization mediated by strain MMB051. On the contrary, the presence of nitrate (NO(3)(-) ) salts as the sole N source affected negatively the ability of MMB051 cells to solubilize inorganic P.