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ABSTRACT: The aim of this work was to evaluate the influence exerted by two different commercial organoclays (DELLITE 43B and DELLITE 67G) on a model microbial consortium using microbial metabolic characterization with BIOLOG system and denaturing gradient gel electrophoresis (DGGE) molecular approach. The information obtained from the molecular analyses, in their complex, account for the differences in species composition induced on the reference consortium by the contact with the organoclays under study. DELLITE 43B resulted to produce a marked selective effect, stimulating the quantitative increase especially of Pseudomonas pseudoalcaligenes. A weaker effect was found for DELLITE 67G. On the other hand, Biolog analyses indicated a depressing action exerted by DELLITE 43B on the metabolic activity of the model microbial consortium as a whole. The presence of P. pseudoalcaligenes and B. borstelensis in the bacterial community after the treatments confirmed that a positive change in the microbial structure consortium occurred.
Environmental pollution (Barking, Essex: 1987) 05/2013; 179C:39-44. · 3.43 Impact Factor
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ABSTRACT: To evaluate the feasibility of using compost to prepare substrates for the disposal of pesticide residues, adsorption and degradation studies were carried out on three widely used agricultural pesticides: chlorpyriphos-methyl, pendimethalin and metalaxyl. Obtained from solid urban waste, this compost has been shown to be able to adsorb high levels of chlorpyriphos-methyl and pendimethalin (85%, 100%) whereas metalaxyl was only adsorbed at a level of 37%. However, adding smectite to the compost increased the adsorption of metalaxyl by 117%. Chlorpyriphos-methyl and pendimethalin degraded quickly with half-lives of 1.7 and 14.5 days, respectively, whereas metalaxyl proved more persistent (a half-life of 84 days). Adding ammonium nitrate to the compost accelerated metalaxyl degradation to a half-life of 15 days.
Journal of Environmental Science and Health Part B Pesticides Food Contaminants and Agricultural Wastes 08/2011; 46(6):454-60. · 1.10 Impact Factor
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ABSTRACT: The disposal problem due to non-degradable petroleum-based plastics has raised the demand for biodegradable polymers. The degradation of poly (lactic acid) (PLA) has been studied for several years, but the understanding of involved mechanisms is still incomplete. Based on our previous studies, and it is hypothesized an enzymatic involvement, the aim of this study was to continue investigations on the degradation of PLA and its nanocomposites by Bacillus licheniformis.
Biodegradation of PLA and its nanocomposites (CLOISITE 30B and SOMASIF MEE) was performed on compression-molded, 25 × 25 × 0.6-mm films. Firstly, two plastic films were dipped into sterile nutrient broth inoculated with B. licheniformis and incubated at 32°C. Then, to verify if biodegradation was due to extracellular esterase, the culture broth was filtered to remove B. licheniformis cells, and the plastic materials were put into this broth.
PLA degradation by B. licheniformis was accelerated by the presence of organoclays. After 5 months in liquid culture, nanocomposites showed only the 10% of residual mass, compared with the 60% of pure PLA. Extracellular esterase activity was detected in the filtered culture broth confirming that PLA biodegradation was probably due to this enzyme action.
Environmental Science and Pollution Research 01/2011; 18(6):865-70. · 2.65 Impact Factor
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ABSTRACT: The aim of this study was to evaluate the effects of the commercial organoclays, CLOISITE 30B, NANOFIL 804 and DELLITE 26C on soil eubacterial community. An enrichment test was carried out on Nutrient Broth containing the organoclay and the microorganisms previously isolated from soil. Four transfers were made, each after 7 days incubation. The molecular analyses on the eubacterial community were performed before treatment and 7 days after each transfer. DNA was extracted, amplified with eubacterial primers, finally analysed by amplified ribosomal DNA restriction analysis (ARDRA) and denaturing gradient gel electrophoresis (DGGE). The profiles of the samples treated with each organoclay showed the absence, the appearance and an increase in the intensity of some bands. These bands were excised from the gels, and the related microorganisms were identified by DNA sequencing, as Pseudomonas putida, Alcaligenes xylosoxidans, Pseudomonas monteilii and Pseudomonas aeruginosa. NAN804 treatment did not have any influence on soil eubacterial community, CLO30B had a slight toxic effect only on P. putida, instead the DEL26C treatment had a stronger toxic effect on P. putida and a slight toxic effect on P. monteilii. Finally, all the tested organoclays stimulated the growth of both A. xylosoxidans and P. aeruginosa.
Journal of hazardous materials 03/2009; 168(1):466-72. · 4.14 Impact Factor
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ABSTRACT: PLA and PCL nanocomposites prepared by adding 5 wt% of a sepiolite (SEPS9) were degraded in compost, leading to effective degradation for all samples.PLA and PLA/SEPS9 seem to be mainly degraded by a bulk mechanism, showing a significant level of polymer degradation, however the presence of SEPS9 particles partially delays the degradation probably due to a preventing effect of these particles on polymer chain mobility and/or PLA/enzymes miscibility. PCL and PCL/SEPS9 showed a preferential surface mechanism of degradation; and in contrast to PLA, sepiolite does not present a considerable barrier effect on the degradation of PCL.
Polymer Degradation and Stability 95(10):2049-2056. · 2.77 Impact Factor
