Chemical composition of rainwater under two events of aerosol transport: A Saharan dust outbreak and wildfires.

A one-year campaign of joint sampling of aerosols and precipitation, carried out in León, Spain, allowed to study the impact of two special events that affected the air quality in the north of the country, on rainfall in the city: a period with wildfires and a Saharan dust intrusion. The wildfires that occurred in northern Portugal and northwestern Spain in August 2016 affected the chemistry of rainfall on 15 August 2016, causing an increase in concentrations of NH4+, Na+, Cl-, K+, Mg2+, Ca2+, SO42- and NO3- and in the concentrations of organic acids, which was reflected in the levels of soluble and insoluble organic carbon. This led to acidification of rainwater (pH = 4.8). The second precipitation event was registered between 11 and 14 February 2017, during which the rainwater was collected in four daily fractions (P1, P2, P3 and P4). The rain sample of 12 February (P2) coincided with a Saharan dust intrusion that reached northern Iberia that day. The chemical composition of P2 showed an increase in the Ca2+ (>800%), Mg2+ (71%), Cl- (62%), and SO42- (33%) concentrations, with respect to P1. The input of crustal elements to the atmosphere helped to neutralize the P2 rainwater, causing pH values higher than 6.5. Once the dust intrusion left the north of the Peninsula, the composition of rainwater P3 and P4 revealed a mixture of marine contribution with local anthropogenic emissions, as well as a decrease in ion concentrations and conductivity, and an increase in pH values.

Influence of design, physico-chemical and environmental parameters on pharmaceuticals and fragrances removal by constructed wetlands.

The ability of several mesocosm-scale and full-scale constructed wetlands (CWs) to remove pharmaceuticals and personal care products (PPCPs) from urban wastewater was assessed. The results of three previous works were considered as a whole to find common patterns in PPCP removal. The experiment took place outdoors under winter and summer conditions. The mesocosm-scale CWs differed in some design parameters, namely the presence of plants, the vegetal species chosen (Typha angustifolia versus Phragmites australis), the flow configuration (surface flow versus subsurface flow), the primary treatment (sedimentation tank versus HUSB), the feeding regime (batch flow versus continuous saturation) and the presence of gravel bed. The full-scale CWs consisted of a combination of various subsystems (ponds, surface flow CWs and subsurface flow CWs). The studied PPCPs were ketoprofen, naproxen, ibuprofen, diclofenac, salicylic acid, carbamazepine, caffeine, methyl dihydrojasmonate, galaxolide and tonalide. The performance of the evaluated treatment systems was compound dependent and varied as a function of the CW-configuration. In addition, PPCP removal efficiencies were lower during winter. The presence of plants favoured naproxen, ibuprofen, diclofenac, salicylic acid, caffeine, methyl dihydrojasmonate, galaxolide and tonalide removal. Significant positive correlations were observed between the removal of most PPCPs and temperature or redox potential. Accordingly, microbiological pathways appear to be the most likely degradation route for the target PPCPs in the CWs studied.

Digestion of cattle manure under mesophilic and thermophilic conditions: characterization of organic matter applying thermal analysis and 1H NMR.

Digestion of cattle manure collected from a livestock farm together with bedding material (straw) has been studied under mesophilic and thermophilic conditions in batch reactors. The digestion was carried out for a prolonged period with the aim of evaluating the changes undergone by the organic matter. The mesophilic digestion carried out revealed a greater capacity to produce gas and transform organic matter, while a higher conversion rate, but a lower gas yield, was obtained under thermophilic conditions. Degradation of the organic matter was evaluated by means of thermal analysis and (1)H NMR. Stabilisation through anaerobic digestion (either mesophilic or thermophilic) resulted in an increase in the quality of the organic matter, as characterised by an enrichment in thermostable compounds, and an accumulation of long chain aliphatic materials. The experiments performed demonstrated the transformation of organic matter into complex materials under anaerobic conditions with an accumulation of aliphatic components under both types of conditions tested. Degradation through mesophilic digestion, in comparison to the thermophilic process, resulted in a greater destruction of straw particles.

Influence of the application of sewage sludge on the degradation of pesticides in the soil.

A study was made of the influence of the application of sewage sludge on the degradation of pesticides in the soil. Two kinds of sludge were used, with different characteristics, one from an urban treatment plant and one from a food processing plant. Three organophosphorus insecticides, fenitrothion, diazinon and dimethoate, were studied. The relative importance was determined of the chemical and biological degradation processes, which involved experiments on soil and sterile soil samples. A comparative study was also made of the degradation of pesticide residues and the evolution of the microbial population. The application of sludge seems to have a complex effect on the degradation of pesticides, determined by the bioavailability and biodegradability of their active ingredient. The biodegradation of pesticide residues brings about alterations in the microorganism population of the soil.

Dye adsorption by sewage sludge-based activated carbons in batch and fixed-bed systems.

The present research work deals with the production of activated carbons by chemical activation and pyrolysis of sewage sludges. The adsorbent properties of these sewage sludges based activated carbons were studied by liquid-phase adsorption tests. Dyes removal from colored wastewater being a possible application for sludge based adsorbents, methylene blue and saphranine removing from solution was studied. Pure and binary adsorption assays were performed in batch and fixed bed systems. In all cases studied, the adsorbents produced from sewage sludges were able to adsorb both the compounds considered here. Nevertheless, time required for reaching equilibrium, adsorptive capacity and fixed bed characteristic parameters were different for these two compounds. Methylene blue adsorption occurred faster than that of saphranine, and it was preferably adsorbed when treating binary solutions. It could be concluded that the sewage sludge-based activated carbons may be promising for dyes removal from aqueous streams.

Quantitative determination of semisynthetic cephamycins in human serum and urine by ion-exchange, reversed-phase and ion-pair chromatography.

High-performance liquid chromatographic methods have been developed for the determination of semisynthetic cephamycins: cefoxitin, cefmetazole and cefminox in human serum and urine samples. Serum samples spiked with each cephamycin were combined with an equal volume of methanol to remove proteins and, after centrifugation, and aliquot of the supernatant was analysed by ion-exchange, reversed-phase and ion-pair chromatography with hexadecyltrimethylammonium bromide as the ion-pairing agent. Urine samples were diluted, filtered and analysed by same chromatographic procedure. The cephamycins were detected by their ultraviolet absorbance (265-272 nm). It was possible to determine concentrations of cephamycins to 0.2 micrograms/ml in serum 2 micrograms/ml in urine samples with a good level of reproducibility and accuracy.

Determination of piperacillin and mezlocillin in human serum and urine by high-performance liquid chromatography after derivatisation with 1,2,4-triazole.

High-performance liquid chromatographic methods have been developed for the determination of piperacillin and mezlocillin in human serum and urine samples. The methods involve ultrafiltration of samples followed by reaction with 1.5 M 1, 2, 4-triazole and 0.5 x 10(-3) M mercury (II) chloride in solution (pH 8.50) at 50 degrees C for 15 min. The resulting products were separated on a C18 column following stabilisation in an eluent containing sodium thiosulphate. They were detected at 323 nm for both penicillins. The methods have been applied to assays applied to assays of these penicillins in human serum and urine samples. The procedures, which permit the determination of penicillin concentration down to 0.1 microgram m1-1 in serum and 1 microgram m1-1 in urine samples, are specific to intact penicillins without interference from corresponding penicilloates [see J. Haginaka et al., Anal. Sci. 1 (1985) 73]. At concentrations of 1-500 micrograms ml-1 for each compound, the within- and between-day precisions were 1.8-4.8 and 3.7-6.9, respectively. The accuracy was ca. 100% for all samples assayed.

Stability in aqueous solution of two monocyclic beta-lactam antibiotics: aztreonam and nocardicin A.

The catalytic effect of various buffer systems (citrates, acetates, phosphates, borates and carbonates) on the degradation of aztreonam and nocardicin A in aqueous solution was studied at 35 degrees C and a constant ionic strength of 0.5 mol.dm-3 over a pH range of 3.50 to 10.50. The observed degradation rates, obtained by measuring the remaining intact antibiotic, were shown to follow pseudo-first-order kinetics with regard to antibiotic concentrations and to be influenced by general acid and general base catalysis. The changes in the concentration of intact beta-lactam antibiotic in the solutions were established by reverse-phase HPLC with UV-detection. In general the buffer systems employed in the kinetic studies showed a very weak catalytic effect on the degradation of aztreonam and nocardicin A. The pH-rate profiles for these antibiotics showed degradation minimums at pH 5.38 and 6.13, respectively. Aztreonam is slightly more reactive with hydrogen ions than nocardicin A and is much more reactive with hydroxide ions. In comparison with other beta-lactamic antibiotics, aztreonam and nocardicin A are much more stable in aqueous solution, except for aztreonam in a base solution, which is just as unstable as penicillins and cephalosporins. The Arrhenius activation energies were determined for aztreonam and nocardicin A at pH's 4.23, 6.59 and 8.60.

Catalysis of hydrolysis and aminolysis of non-classical beta-lactam antibiotics by metal ions and metal chelates.

The Zn(2+)-tris (hydroxymethyl)aminomethane (Tris) system has a great catalytic effect on the hydrolysis and aminolysis of some beta-lactam antibiotics. In order to ascertain the mechanism of this catalysis we have analysed the effects of the beta-lactam antibiotic structure. First we studied the kinetics of the decomposition of imipenem, SCH 29482, aztreonam and nocardicin A in aqueous solution of Tris at 35.0 degrees C, 0.5 mol.dm-3 ionic strength and in the presence of metal ions (Zn2+, Cd2+, Co2+, Cu2+, Ni2+ and Mn2+). From these studies, we conclude that Tris and metal ions (in separate solutions) exert a great catalytic effect on the hydrolysis of imipenem and SCH 29482. We suggest that in metal ion solutions a 1:1 complex is formed between the metal ion and beta-lactam antibiotic, which is attacked by hydroxide ions. Studies of the degradation of the antibiotics studied in solutions of Tris and metal ions together indicate that the systems Cd(2+)-Tris and Zn(2+)-Tris have a great catalytic effect on the hydrolysis and aminolysis of imipenem and SCH 29482. We suggest that this catalysis takes place via a ternary complex in which the metal ion plays a double role by (a) placing the antibiotic and the Tris in the right position for the reaction and (b) lowering the pKa of the hydroxide group of Tris, which is coordinated with the metal ion, generating a strong nucleophile.

High-performance liquid chromatographic methods for the determination of the penems SCH 29482 and FCE 22101 in human serum and urine.

High-performance liquid chromatographic methods have been developed for the determination of two 6-(1-hydroxyethyl)penems, SCH 29482 (I) and FCE 22101 (II), in serum and urine. Serum samples were combined with an equal volume of methanol to remove proteins and, after centrifugation, an aliquot of the supernatant was analysed by ion-pair chromatography on a reversed-phase C18 column with hexadecyltrimethylammonium bromide as the ion-pairing agent. The compounds were detected by their ultraviolet absorbance at 305 nm for II and 322 nm for I. Urine samples were diluted, filtered and analysed by the same chromatographic procedure. At concentrations of 1-500 micrograms/ml of each compound, the within- and between-day precisions were 1.8-3.6 and 2.6-5.1%, respectively. The detection limit was 0.2 micrograms/ml for I and 0.3 micrograms/ml for II.

Interaction of beta-lactamases I and II from Bacillus cereus with semisynthetic cephamycins. Kinetic studies.

The influence of C-6 alpha- or C-7 alpha-methoxylation of the beta-lactam ring in the catalytic action of class A and B beta-lactamases has been investigated. For this purpose the kinetic behaviour of beta-lactamases I (class A) and II (class B) from Bacillus cereus was analysed by using several cephamycins, moxalactam, temocillin and related antibiotics. These compounds behaved as poor substrates for beta-lactamase II, with high Km values and very low catalytic efficiencies. In the case of beta-lactamase I, the substitution of a methoxy group for a H atom at C-7 alpha or C-6 alpha decreased the affinity of the substrates for the enzyme. Furthermore, the acylation of cephamycins was completely blocked, whereas that of penicillins was slowed down by a factor of 10(4)-10(5), acylation being the rate-determining step of the process.

Synthesis of 3-furylmethylpenicillin using an enzymatic procedure.

3-Furylmethylpenicillin was synthesized in vitro from 3-furylacetic acid, 6-aminopenicillanic acid (6-APA), CoA, ATP and Mg2+. The reaction was catalyzed in two steps by the enzymes phenyl-acetyl-CoA ligase (PCL) from Pseudomonas putida and acyl-CoA: 6-APA acyltransferase (AT) from Penicillium chrysogenum. PCL catalyzes the activation of 3-furylacetic acid to 3-furylacetyl-CoA (3-F-CoA) and AT acylates the amino group of 6-APA with the 3-furylacetyl moiety of 3-F-CoA, releasing CoA and 3-furylmethylpenicillin.

Acyl-CoA: 6-APA acyltransferase from Penicillium chrysogenum studies on its hydrolytic activity.

Acyl-CoA: 6-APA acyltransferase (AT) from Penicillium chrysogenum Wis 54-1255 catalyzes the hydrolysis of different acyl-CoA derivatives generating, in the absence of 6-APA, free acid and CoA. The hydrolytic efficiency of AT is highest for acyl-CoA variants in which the acyl-moiety is higher than six carbon atoms. The maximal rate of catalysis was achieved in 50 mM Tris-HCl buffer, pH 8.5 at 35 degrees C. Unlike the AT activity, the acylase activity has a different optimum temperature and substrate specificity and dithiothreitol is not required for the reaction.

Aliphatic molecules (C-6 to C-8) containing double or triple bonds as potential penicillin side-chain precursors.

Three different hexenoyl-CoA derivatives (trans-2-hexenoyl-CoA, trans-3-hexenoyl-CoA and trans-trans-2,4-hexadienoyl-CoA), two octenoyl-CoA (trans-2-octenoyl-CoA, trans-3-octenoyl-CoA) and 2-octynoyl-CoA were tested as substrates of the enzyme acyl-CoA: 6-Aminopenicillanic acid acyltransferase (AT) from Penicillium chrysogenum. Only trans-3-hexenoyl-CoA and trans-3-octenoyl-CoA were recognized by AT and efficiently converted into penicillin F and octenoylpenicillin, respectively. The Km values for these substrates were 0.6 and 0.5 mM, suggesting that the affinity of AT for these molecules is similar to that reported for phenyl acetyl-CoA, octanoyl-CoA and hexanoyl-CoA (0.5, 0.6, and 1 mM, respectively). The absence of enzymatic activity shown by AT with the other acyl-CoA derivatives tested is due to the different position of the double or triple bond(s) in their aliphatic chains. The influence of the free rotation round the bond C-2-C-3 and possibility of planar conformation in such molecules and the importance in the formation of the enzyme-substrate complex is discussed.

Design of an enzymatic hybrid system: a useful strategy for the biosynthesis of benzylpenicillin in vitro.

A hybrid (prokaryotic-eukaryotic) enzyme system leading to the production of benzylpenicillin has been developed. In vitro synthesis of penicillin G was achieved by incubating 6-aminopenicillanic acid, CoA, phenylacetic acid, homogeneously pure phenylacetyl-CoA ligase (PA-CoA ligase) from Pseudomonas putida and acyl-CoA:6-APA acyltransferase (AT) from Penicillium chrysogenum. Benzylpenicillin was also obtained when AT was coupled with PA-CoA ligase and isopenicillin N-synthetase (IPNS). This is the first description of an in vitro assay that, using enzymes of different microbial origin, mimics the three last enzymatic steps leading to the biosynthesis of penicillin G in P. chrysogenum.

Biosynthesis of benzylpenicillin (G), phenoxymethylpenicillin (V) and octanoylpenicillin (K) from glutathione S-derivatives.

"In vitro" synthesis of benzylpenicillin and phenoxymethylpenicillin has been carried out by direct N-acylation of 6-aminopenicillanic acid (6-APA) with S-phenylacetyl- and (S-phenoxyacetyl)glutathione. The reactions were catalyzed by the enzyme acyl-CoA: 6-APA acyltransferase (AT) from Penicillium chrysogenum and in both cases the synthesis of antibiotics was enhanced by CoA. Penicillin K, a natural penicillin, was also synthesized "in vitro" by incubating (S-octanoyl)glutathione, 6-APA and AT, but in this case the formation of antibiotic required the presence of CoA. Furthermore, benzylpenicillin was obtained from (S-phenylacetyl)cysteinylglycine and 6-APA, suggesting that some intermediates of the gamma-glutamyl cycle are directly involved in the biosynthesis of penicillins. To explain "in vivo" formation of this beta-lactam antibiotic, a biosynthetic pathway which includes several glutathione-S-derivatives and a non-enzymatic reaction, is proposed.

IV. Acyl-CoA: 6-APA acyltransferase of Penicillium chrysogenum: studies on substrate specificity using phenylacetyl-CoA variants.

Two different penicillins (p- and m-methylbenzylpenicillin) were obtained "in vitro" by direct enzymatic synthesis, using homogeneously pure acyl-CoA: 6-aminopenicillanic acid (6-APA) acyltransferase from Penicillium chrysogenum, 6-APA and p- or m-tolylacetyl-CoA. The Km for these substrates were 6 and 15 mM, respectively, indicating that the affinity of the enzyme for these two molecules is much lower that shown by phenylacetyl-CoA (0.55 mM). Furthermore, acyltransferase does not recognize o-tolylacetyl-CoA as a substrate suggesting that the position of the methyl group on the aromatic moiety may have a very important role in the formation of the enzyme-substrate complex.