1,721,487 research outputs found
Use of exogenous specialised bacteria in the biological detoxification of a dump site-polychlorobiphenyl-contaminated soil in slurry phase conditions
No full textThe possibility of biologically detoxifying a contaminated soil from an Italian dump site containing about 1500 mg/kg (in dry soil) of polychlorinated biphenyls was studied in the laboratory in this work. The soil, which contained indigenous aerobic bacteria capable of growing on biphenyl or on monochlorobenzoic acids at concentration of about 300 CFU per g of air-dried soil, was amended with inorganic nutrients, saturated with water and treated in aerobic 3-L batch slurry reactors (soil suspension at 20% w/v). Either Pseudomonas sp. CPE1 strain, capable of cometabolising low- chlorinated biphenyls into chlorobenzoic acids, or a bacterial coculture capable of aerobically dechlorinating polychlorobiphenyls constituted by this bacterium and the two chlorobenzoic acid degrading bacteria Pseudomonas sp. CPE2 strain and Alcaligenes sp. CPE3 strain, were used as inocula (final concentration of about 108 CFU/mL for each bacterium), in the absence and in the presence of biphenyl (4 g/kg of air dried soil). Significant soil polychlorobiphenyl depletions were observed in all the reactors after 119 days of treatment. The soil inoculation with the sole CPE1 was found to slightly enhance the polychlorobiphenyl depletions (about 20%) and the soil detoxification; the effect was higher in the presence of biphenyl. The use of the polychlorobiphenyl mineralising bacterial co-culture as inoculum resulted in a strong enhancement of the depletions of both the soil polychlorobiphenyls (from 50 to 65%) and of the original soil ecotoxicity. The bacterial biomass inoculated was found to implant into the soil; the higher specialised biomass availability thus reached in the inoculated soil was probably responsible of a more extensive biodegradation of polychlorobiphenyls and therefore of the higher detoxification yields observed in the inoculated reactors. The soil ecotoxicity, measured through two different soil contact assays, i.e., the Lepidium sativum germination test and the Collembola mortality test, was often found to decrease proportionally with the soil polychlorobiphenyl concentration
Storia della notte. Testo spagnolo a fronte
No full textIl volume è l’edizione italiana della raccolta poetica Historia de la noche (1977) dello scrittore argentino Jorge Luis Borges. La traduzione metrica delle poesie che compongono la raccolta è accompagnata da una Nota al testo di natura critico-filologica
Intestinal microbiota in inflammatory bowel disease: Friend of foe?
No full textInflammatory bowel disease (IBD) arises from disruption of immune tolerance to the gut commensal microbiota, leading to chronic intestinal inflammation and mucosal damage in genetically predisposed hosts. In healthy individuals the intestinal microbiota have a symbiotic relationship with the host organism and possess important and unique functions, including a metabolic function (i.e. digestion of dietary compounds and xenobiotics, fermentation of undigestible carbohydrates with production of short chain fatty acids), a mucosal barrier function (Le. by inhibiting pathogen invasion and strengthening epithelial barrier integrity), and an immune modulatory function (i.e. mucosal immune system priming and maintenance of intestinal epithelium homeostasis). A fine balance regulates the mechanism that allows coexistence of mammals with their commensal bacteria. In IBD this mechanism of immune tolerance is impaired because of several potential causative factors. The gut microbiota composition and activity of IBD patients are abnormal, with a decreased prevalence of dominant members of the human commensal microbiota (i.e. Clostridium IXa and IV groups, Bacterades, bifidobacteria) and a concomitant increase in detrimental bacteria (i.e. sulphate-reducing bacteria, Escherichia cob). The observed dysbiosis is concomitant with defective innate immunity and bacterial killing (i.e. reduced mucosal defensins and IgA, malfunctioning phagocytosis) and overaggressive adaptive immune response (due to ineffective regulatory T cells and antigen presenting cells), which are considered the basis of IBD pathogenesis. However, we still do not know how the interplay between these parameters causes the disease. Studies looking at gut microbial composition, epithelial integrity and mucosal immune markers in genotyped IBD populations are therefore warranted to shed light on this obscure pathogenesis. (C) 2011 Baishideng. All rights reserved
Growth of Rhodosporidium toruloides strain DBVPG 6662 on dibenzothiophene crystals and orimulsion.
No full textA multi-step physicochemical-biotechnological approach for the valorization of olive mill wastewaters
No full textWaste valorization processes carried out through integrated multi-step biorefinery approaches can allow a massive exploitation of the waste organic matter. Olive mill wastewaters (OMWs) are agro-industrial wastes of a high environmental concern. A relevant part of their high COD is typically due to polyphenolic compounds, which are known to be toxic if concentrated to such extents. On the other hands, polyphenols are natural antioxidants of special relevance for several industrial sectors. Therefore, their recovery from OMWs provides the double opportunity to obtain high-added value biomolecules and to reduce the phytotoxicity of the effluent. To such an aim, an effective solid phase extraction process was recently developed [1]. The first aim of the present work was to define a protocol for the recovery and reuse of both the adsorbent (Amberlite XAD16 non-polar resin) and extraction solvent (ethanol), in order to verify the feasibility of a possible process scale-up. Very encouraging results were obtained: ethanol was recovered by means of a rotary evaporator, thus obtaining a concentrated phenolic mixture, whose antioxidant properties were demonstrated via ORAC and DPPH assays; furthermore, after its employment, the resin was washed with a sulphuric acid solution and regenerated: no significant losses of the resin adsorption capabilities were observed after 10 operation cycles. The exploitation of the OMW organic matter was further addressed toward the biotechnological production of biobased chemicals, such as H2 and volatile fatty acids (VFAs), which represent a feasible substrate for aerobic bacteria able to produce and store biopolymers such as polyhydroxyalkanoates (PHAs) [3]. A non conventional anaerobic digestion process carried out under acidogenic conditions for the obtainment of VFAs from dephenolized OMWs was recently developed [4]. The second aim of the present study was a further assessment of that process, with the aim of minimizing the process HRT. At a HRT = 5 days, a stable process capable of an effective bioconversion of the OMW organic matter into VFAs was obtained, with a VFA final concentration of about 19.7 gCOD/L, representing about 83% of the overall effluent COD.
References
[1] Bertin, L., Ferri, F., Scoma, A., Marchetti, L., Fava, F.: Recovery of high added value natural polyphenols from actual olive mill wastewater through solid phase extraction. Chem. Eng. J. 171, 1287-1293 (2011)
[2] Beccari, M., Bertin, L., Dionisi, D., Fava, F., Lampis, S., Majone, M., Valentino, F., Vallini, G., Villano, M.,: Exploiting olive oil mill effluents as a renewable resource for production of biodegradable polymers through a combined anaerobiceaerobic process. J. Chem. Technol. Biotechnol. 84, 901-908 (2009)
[3] Scoma, A., Bertin, L., Zanaroli, G., Fraraccio, S., Fava, F.: A physicochemical–biotechnological approach for an integrated valorization of olive mill wastewater. Biores. Technol. 102, 10273-10279 (2011
Repeated batch approach as a feasible procedure for the acclimatization of anaerobic consortia capable of an effective biomethanization of mechanically-sorted organic fraction of municipal solid waste
No full textThe acclimatization of anaerobic consortia capable of an effective biomethanization of a mechanically sorted-organic fraction of municipal solid waste (MS-OFMSW) was achieved in this study by following a repeated batch co-digestion approach. Mixtures of MS-OFMSW and cattle manure were processed in successive batch anaerobic digestion processes. Such an approach generally allowed a significantly increasing of the methane production when the MS-OFMSW represented the 30 and 40 % (v/v) of the initial mixture. On the other hand, the acclimated inocula did not adapt efficiently to higher concentration of the target waste MS-OFMSW. The acclimatization of the anaerobic consortia was demonstrated by means of molecular biology tools, by which a high diversity among populations occurring in the experimental matrices and after anaerobic processes was observed
A chemical-biological integrated approach for the valorization of olive mill wastewaters
No full textAn integrated chemical-biological process for the recovery of natural phenolic compounds from an olive mill wastewater (OMW) and for the anaerobic production of volatile fatty acids (VFAs) from the pre-treated OMW was developed in this work. The recovery of OMW polyphenols was carried out through solid phase extraction (SPE) by
using Amberlite XAD16 resin as the adsorbent and ethanol as the biocompatible desorbing phase. Thereafter, the acidogenic digestion of the dephenolized OMW was performed in a mesophilic packed-bed biofilm reactor filled with ceramic cubes, who was operated at an OLR of about 5.9 g L-1 day-1. As a result of the integrated process, more than 60% of polyphenols were recovered and 19 gCOD L-1 of VFAs were obtained, representing more than 70% of the anaerobic effluent COD
Enhancement of microbial reductive dechlorination of polychlorinated biphenyls in a marine sediment by nanoscale zerovalent iron particles
No full textZerovalent iron is known to effectively dechlorinate many halogenated aliphatic and aromatic hydrocarbons via direct reductive reaction, as well as to be oxidized by water with the production of hydrogen gas, i.e., the preferential electron donor for many dehalorespiring bacteria. In this work, we evaluated the effect of nanoscale zerovalent iron (NZVI) particles on the reductive dechlorination of polychlorinated biphenyls (Aroclor 1254) in anaerobic slurry microcosms of a marine sediment suspended in the site water, i.e., under in situ-like biogeochemical conditions. No abiotic dechlorination and a four-fold increase in the extent and rate of the microbial reductive dechlorination process was observed in the presence of NZVI particles. NZVI also influenced the sulfate-reduction and methanogenic processes, which were both partially inhibited, and the composition of the indigenous bacterial community, leading to the enrichment of the PCB-dechlorinating bacterium Dehalobium chlorocoercia DF-1
Anaerobic biodegradation of weathered polychlorinated biphenyls (PCBs) in contaminated sediments of Porto Marghera (Venice Lagoon, Italy)
No full textThe biodegradation of weathered polychlorinated biphenyls (PCBs) (mono and di-chlorinated biphenyls along with PCBs partially ascribed to Aroclor 1242 and 1254) occurring at 1.5-2.5 mg/kg in three different sediments collected from the Porto Marghera contaminated area of Venice Lagoon (Italy) was reported in this study. Strictly anaerobic, slurry microcosms consisting of sediments suspended (at 25% v/v) in a marine salt medium, lagoon water or lagoon water supplemented with NaHCO3 and Na2S were developed and monitored for PCB transformation, sulfate consumption and methane (CH 4) production for 6 months. A marked depletion of highly chlorinated biphenyls along with the accumulation of low-chlorinated, often ortho-substituted biphenyls was observed in the biologically active microcosms, where a remarkable consumption of sulfate and/or a significant production of CH4 were also detected. Notably, a more extensive PCB transformation was observed in the microcosms developed with site water (both without or with NaHCO3 plus Na2S), where both the initial concentration of sulfate and sulfate consumption were five fold-higher than in the corresponding microcosms with salt medium. These data indicate that weathered PCBs of the three contaminated sediments of Porto Marghera utilized in this study can undergo reductive dechlorination, probably mediated by indigenous sulfate-reducing and/or methanogenic bacteria. © 2003 Elsevier Ltd. All rights reserved
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