Cytotoxic and clastogenic effects of soluble chromium compounds on mammalian cell cultures.

The inhibition of cell growth, the reduction of cell survival and the induction of chromosome aberrations and of sister chromatid exchange (SCE) have been determined in cultured hamster cell lines (BHK and CHO) treated with 11 water-soluble compounds of hexavalent and trivalent chromium. All Cr6+ compounds inhibit growth of BHK cells and reduce survival of CHO cells to levels comparable to those obtained only after exposure to 100--1000 times higher Cr3+ concentrations. The cytotoxicity curves obtained with the different Cr6+ compounds are almost overlapping, whereas marked differences of activity are noticeable among Cr3+ compounds. Giant cells are obtained after exposure to Cr6+ and Cr3+ compounds, as shown by the rise of DNA and RNA per cell, and are due to the blockage of the cell cycle without sudden inhibition of macromolecular syntheses. Both Cr6+ and Cr3+ compounds are able to induce chromosome aberrations, whereas Cr3+ is absolutely incapable of inducing SCE, only Cr6+ being active. The frequency of chromosome aberrations is increased about 10-fold after exposure to 1.0 micrograms/ml Cr6+, whereas it is only doubled after treatment with up to 150 micrograms/ml Cr3+. On the other hand, in spite of the sensitivity of CHO cells to the induction of SCE by mitomycin C, the frequency of SCE hardly doubles after exposure to Cr6+ compounds. The present data confirm that Cr6+ compounds are characterized by a marked cytotoxicity and clastogenic action on mammalian cell cultures and show that Cr3+ compounds, though cytotoxic only at extremely high concentrations and not increasing the frequency of SCE, are not completely without cytogenetic effect, as they are able to induce chromosome aberrations

Cytotoxic and clastogenic effects of soluble and insoluble compounds containing hexavalent and trivalent chromium.

Cr(III) and Cr(VI) compounds of varying solubilities have been tested in vitro for their ability to inhibit cell growth and nucleic acid and protein syntheses in BHK cells, to induce alterations in the mitotic cycle in HEp cells, and to increase the frequency of chromosomal aberrations and sister chromatid exchanges (SCE) in CHO cells. All Cr(VI) compounds, and particularly those containing soluble Cr(VI), such as potassium dichromate and zinc yellow, differentially inhibit macromolecular syntheses in BKH cells, that of DNA being always the most affected. Among Cr(III) compounds, which generally have very low cytotoxicity, chromite is particularly active, and inhibits cell growth and DNA synthesis even more than the poorly soluble Cr(VI) compounds. Preincubation in growth medium, with or without metabolizing cell cultures, solubilizes considerable amounts of Cr(VI) from zinc yellow and chromite, but significant amounts are also obtained from the most insoluble Cr(VI) pigments. When BHK cells are treated with such preincubated solutions, reduction of soluble Cr(VI) to Cr(III) by cell metabolites is seen with all Cr(VI) compounds, accompanied by decreased cytotoxicity. The same differences between Cr(VI) and Cr(III) compounds apply to the cytotoxic effects on mitosis of HEp cells and the clastogenic effects on CHO cells. The activity of chromite, the only Cr(III) pigment capable of significantly increasing the frequency of SCE, is due to contamination with soluble Cr(VI). In contrast to the very low cytotoxicity of Cr(III), much higher chromium levels are detected in the cells incubated with soluble Cr(III) than with the same concentrations of soluble Cr(VI). 50% and 75% of chromium accumulated in the cells during treatments with Cr(VI) and Cr(III) respectively remains firmly bound to the cells, even when they are incubated for up to 48 h in normal growth medium. Chromium accumulated in the cells after treatment with Cr(III) is most probably bound to the cell membrane, whereas some of the Cr(VI) is transported through the cell membrane and reduced in the cell nucleus. The results of the present investigation are in agreement with those obtained with the same Cr(VI) and Cr(III) compounds in mutagenicity assays in bacteria and carcinogenicity tests in rodents. A re-evaluation of the mechanisms of chromium carcinogenisis is proposed

Digestión anaerobia termófila de fangos a escala industrial: Efecto de la co-digestión con residuos agroalimentarios

Se ha llevado a cabo un estudio en un digestor industrial de 2500 m3 con el fin de mejorar la gestión medioambiental de efluentes líquidos y residuos sólidos en una fábrica de alimentos precocinados pasando de la digestión anaerobia de los fangos procedentes del tratamiento de aguas residuales a la co-digestión anaerobia en presencia de residuos agroalimentarios de la misma fábrica, funcionando ambos procesos en condiciones termófilas.El objetivo de tal acción ha sido minimizar la cantidad de residuos a tratar en la misma fábrica (o a enviar fuera de la misma para su gestión ulterior) y, también, recuperar la energía presente en tales residuos mediante generación de biogás. Se ha demostrado que la substitución de fango por residuos agroalimentarios no merma la producción de biogás, al haberse demostrado que el caudal de biogás permanece prácticamenteconstante (1678 ± 99 m3/día y 1623 ± 147 m3/día, medidosen condiciones estándar de 1 bar y 0 ºC, para la digestión y co-digestión, respectivamente). Ahora bien, la co-digestión fue más eficaz en lo que a eliminación de sólidos se refiere y el rendimiento de eliminación de sólidos totales aumentó del 58,8% (digestión) al 65,0% (codigestión) y el rendimiento de eliminación de sólidos volátiles se incrementó del 66,9 al 72,8%. Así pues, se ha demostrado el buen funcionamiento del digestor anaerobio termófilo al añadir residuos agroalimentarios al fango con el que operaba habitualmente. Mediante análisislineal múltiple ha sido posible predecir el caudal de biogás  y el rendimiento de eliminación de sólidos en función de diferentes variables de proceso

Modelling Mixed Microbial Culture Polyhydroxyalkanoate Accumulation Bioprocess towards Novel Methods for Polymer Production Using Dilute Volatile Fatty Acid Rich Feedstocks

Volatile fatty acid (VFA) rich streams from fermentation of organic residuals and wastewater are suitable feedstocks for mixed microbial culture (MMC) Polyhydroxyalkanoate (PHA) production. However, many such streams have low total VFA concentration (1–10 gCOD/L). PHA accumulation requires a flow-through bioprocess if the VFAs are not concentrated. A flow through bioprocess must balance goals of productivity (highest possible influent flow rates) with goals of substrate utilization efficiency (lowest possible effluent VFA concentration). Towards these goals, dynamics of upshift and downshift respiration kinetics for laboratory and pilot scale MMCs were evaluated. Monod kinetics described a hysteresis between the upshift and downshift responses. Substrate concentrations necessary to stimulate a given substrate uptake rate were significantly higher than the concentrations necessary to sustain the attained substrate uptake rate. A benefit of this hysteresis was explored in Monte Carlo based PHA accumulation bioprocess numerical simulations. Simulations illustrated for a potential to establish continuous flow-through PHA production bioprocesses even at a low (1 gCOD/L) influent total VFA concentration. Process biomass recirculation into an engineered higher substrate concentration mixing zone, due to the constant influent substrate flow, enabled to drive the process to maximal possible PHA production rates without sacrificing substrate utilization efficiency

Ethylic esters as green solvents for the extraction of intracellular polyhydroxyalkanoates produced by mixed microbial culture

Volatile fatty acids obtained from the fermentation of the organic fraction of municipal solid waste can be used as raw materials for non-toxic ethyl ester (EE) synthesis as well as feedstock for the production of polyhydroxyalkanoates (PHAs). Taking advantage of the concept of an integrated process of a bio-refinery, in the present paper, a systematic investigation on the extraction of intracellular poly(3-hydroxybutyrate-co-3-hydroxyvalerate), produced by mixed microbial culture by using EEs was reported. Among the tested EEs, ethyl acetate (EA) was the best solvent, dissolving the copolymer at the lowest temperature. Then, extraction experiments were carried out by EA at different temperatures on two biomass samples containing PHAs with different average molecular weights. The parallel characterization of the extracted and non-extracted PHAs evidenced that at the lower temperature (100◦C) EA solubilizes preferentially the polymer fractions richer in 3HV comonomers and with the lower molecular weight. By increasing the extraction temperature from 100◦C to 125◦C, an increase of recovery from about 50 to 80 wt% and a molecular weight reduction from 48% to 65% was observed. The results highlighted that the extracted polymer purity is always above 90 wt% and that it is possible to choose the proper extraction condition to maximize the recovery yield at the expense of polymer fractionation and degradation at high temperatures or use milder conditions to maintain the original properties of a polymer

Bioelectrochemical dechlorination of trichloroethene: From electron transfer mechanisms to process scale-up

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Field distribution and activity of chlorinated solvents degrading bacteria by combining CARD-FISH and real time PCR

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Wireless Sensor Network Deployment for Monitoring Soil Moisture Dynamics at the Field Scale

AbstractWe describe the deployment of a Wireless Sensor Network (WSN), composed of 135 soil moisture and 27 temperature sensors, in an apple tree orchard of about 5000 m2, located in the municipality of Cles, a small town in the Alpine region, northeastern Italy. The orchard is divided into three parcels each one subjected to a different irrigation schedule. The objective of the present work is to monitor soil moisture dynamics in the top soil to a detail, in both space and time, suitable to analyze the interplay between soil moisture dynamics and plant physiology. The deployment consists of 27 locations (verticals) connected by a multi hop WSN, each one equipped with 5 soil moisture sensors deployed at the depths of 10, 20, 30, 50 and 80 cm, and a temperature sensor at the depth of 20 cm. The proposed monitoring system is based on totally independent sensor nodes, which allow both real time and historic data management and are connected through an input/output interface to a WSN platform. Meteorological data are monitored by a weather station located at a distance of approximately 100 m from the experimental site.Great care has been posed to calibration of the capacitance sensors, both in the laboratory, with soil samples, and on site, after deployment, in order to minimize the noise caused by small oscillations in the input voltage and uncertainty in the calibration curves. In this work we report the results of a preliminary analysis on the data collected during the growing season 2009. We observed that the WSN greatly facilitates the collection of detailed measurements of soil moisture, thereby increasing the amount of information useful for exploring hydrological processes, but they should be used with care since the accuracy of collected data depends critically on the capability of the system to maintain constant the input voltage and on the reliability of calibration curves. Finally, we studied the spatial and temporal distribution of soil moisture in all the irrigated parcels, and explored how different irrigation schedules influence orchard's production

Coupled Biological and Thermochemical Process for Plastic Waste Conversion into Biopolymers

The aqueous phase produced from the hydrothermal liquefaction (HTL) of three matrices (Plasmix treated with different operative conditions and polystyrene) was subjected to acidogenic fermentation (AF) batch tests to obtain organic acids, which are the ideal substrates for biopolymers (e.g., polyhydroxyalkanoates, PHA) production from mixed microbial cultures (MMC). Parallel tests in the presence of only HTL water fractions or only glucose (an easily biodegradable compound), or in presence of both, were conducted and compared to assess any possible recalcitrant or inhibitory effect of plastic waste from the HTL treatment during the AF process. These tests resulted, within approximately 30 days of operation, in a conversion of 96 ± 21% (COD/COD) of the Plasmix by-products after a 2h thermochemical treatment into organic acids, a 54 ± 7% (COD/COD) of conversion for Plasmix by-products treated 4h, and 29 ± 1% (COD/COD) of conversion in the presence of polystyrene residual water

Polyhydroxyalkanoate (PHA) production from sludge and municipal wastewater treatment

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