1,721,068 research outputs found
Impiego di Sistemi Enzimatici Fenolossidanti in Forma Libera e Immobilizzata nel Trattamento di Reflui Agroindustriali e di Molecole Recalcitranti
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Trattamento Fungino o enzimatico di un refluo agroindustriale per la rimozione del potenziale fitotossico
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Modifiche nell’impronta microbica di un suolo naturale in seguito alla contaminazione con Escherichia Coli
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Contaminazione dei prodotti agricoli da arsenico: assimilazione e strategie di mitigazione
No full textArsenic (As) is an element widely distribu- ted in air, soil, rocks and water. Its presence is due to both the volcanic character of the soil and the erosion of rocks. The highest concentration of this element is found in groundwater. The presence of As in water is mainly due to either natural release of the minerals from the soil (volcanic rocks and iron minerals) or to geothermal activity. The presence of As is also linked to human activities, such as energy production throu- gh coal-fired power plants and other fuels derived from fossil fuels, smelters, waste incineration and use of pesticides in agriculture. In the environment As undergoes oxidation, reduction, methylation and demethylation. The oxidation states are: -3, 0, +3 (arsenite) and +5 (arsenate). Commonly As binds to iron, oxygen and sulfur, which form organic and inor- ganic compounds in different oxidation states. Arsenic is extremely toxic, but the toxicological effects are clo- sely related to the chemical form: inorganic com- pounds have been identified as the most toxic, fol- lowed by organic and finally by arsine gas. The toxi- city varies fact, in descending order to the various forms of speciation. For humans the main source of environmental exposure to As is drinking water, where it is present in inorganic form: both as trivalent arsenic As(III) and pentavalent arsenic As(V), but also through the air and food. Arsenic enters the food chain throu- gh plant crops, which absorb it through their roots according to its bioavailable levels in soils. Arsenate is transported by roots via phosphate transporters, while arsenite is taken up by a subclass of aquaporins (NIP), some of them also transporting silicon (Si). Methylated forms of As (MetAs) are also taken up by NIP and Si transporters. Inside plants, these types of transporters are also involved in the distribution of As between organs and tissues. However, different forms of As have different mobility efficiencies. Crops exhibit different tendencies to accumulate As in different plant parts in their order: root > stem > leaf . As(V) is enzy- matically reduced into As(III) in plant cells by arsenate reductase (AR), leading to the conversion of glutathio- ne (GSH) to its oxidized form (GSSG). Arsenite can be effluxed to the environment by a root Si transporter or methylated. Another pathway of detoxification occurs by the synthesis of phytochelatins (PCs). PC synthesis and their complexation to As(III) are coordi- nated to the transport of the PC–As(III) complex to the vacuole. For a proper assessment of risk/toxicity of a polluted As soil and to predict its attenuation, after application of remediation techniques, it is crucial to establish the mobility, phytoavailability and biogeoche- mistry of the toxic element. In this review we describe the mechanisms of transport, metabolism and toleran- ce that plants show in response to As. Some strate- gies to reduce As in soil and its transport in plant crops are also summarized
Ottimizzazione di un trattamento defenolante sulle acque reflue di frantoio mediante analisi delle superfici di responso
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Laccase-catalyzed removal of 2,4- dichlorophenol in the presence of polyethylene glycol
No full textThe effect of the additive, polyethylene glycol 4000 (PEG), on the laccase-catalyzed removal of 2,4-dichlorophenol (DCP) from synthetic wastewaters was studied over the DCP concentration range 2-16 mM. Results showed that PEG had a significant protective effect on laccase activity. The amount of enzyme required to obtain 50% pollutant removal was reduced 35-, 39- and 20-fold less than that required without PEG for 4, 8 and 16 mM DCP solutions, respectively
Valorizzzione di residui agricoli nella produzione di enzimi in condizioni di fermentazione solida
No full textEffect of additives on enzyme-catalyzed polymerization of phenols and aromatic amines
No full textAmong biological approaches to the removal of aromatic amines and phenols from wastewater, the socalled enzyme-catalyzed polymerization and precipitation (ECPP) process relies on the use of oxidoreductases acting via radical mechanisms and characterized by a rather relaxed substrate specificity, such as laccase, tyrosinase and heme-peroxidases. The main technical constraints of ECPP processes are due to a variety of enzyme deactivation phenomena occurring during catalysis and to the incomplete removal of oxidation products from solution. In order to put ECPP into practice, these drawbacks have to be either counteracted or minimized. Although several approaches, such as enzyme immobilization and reaction engineering, have been proposed to limit these constraints, this review is intended to provide a wide survey on some chemical additives with either protective or coagulating effects that have been so far employed for these purposes
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