Enzymes of Significance to the Restoration of Polluted Systems: Traditional and Advanced Approaches.

Extensive research efforts have been directed toward the search for novel methods to remediate polluted environments. The use of microorganisms (bioremediation) and plants (phytoremediation) to remediate polluted environments is a promising and growing area of environmental biotechnology. They have a potential to remove pollutants from the environment without harsh side effects and may be utilized in situ, i.e. in the contaminated place itself, offering numerous advantages over ex situ technologies. Intra-, ecto- and extra-cellular enzymes are, ultimately, the main effectors of pollutant transformation during plant and/or microbial processes. Enzymes are the proximate agents of organics transformation in soils; their production (mainly of extra-cellular enzymes) is controlled by several factors including at the organism level the pairing of low-level constitutive synthesis with induction-repression pathways, and at the microbial population and community levels the quorum-sensing systems that regulate unique and varied cellular responses as well as protection from competing microbial communities. Traditional and advanced approaches are available not only to increase and improve the performance of enzymes for their practical, successful application but also to monitor their effectiveness in the restoration of polluted environment. In particular, recent technological advances in molecular biology and proteomics may provide new tools that are applicable to enzyme studies

Enzymatic bioremediation of recalcitrant compounds

The potentialities of intracellular and extracellular enzymes in the detoxification of organic pollutants are well documented. Experimental evidence is also available of their use for an effective transformation of recalcitrant compounds. These latter have potential significant impact on human and environmental health, because they are resistant to environmental degradation and therefore they may persist in the environment, may bioaccumulate in human and animal tissue, and may biomagnify in food chains. Negative, often irreversible effects on the environment may result. In this presentation some groups of recaciltrant organic pollutants will be considered, and recent findings on the enzymes involved in their transformation and possibly utilizable for their remediation will be examined. The compounds will be selected among those considered priority pollutants by National and International Environmental Agencies. Particular attention will be devoted to drawbacks and limits that still hinder the widespread use of enzymes as detoxifying agents of sites polluted by such compounds. The experimental procedures capable of actually establishing the involvement of enzymes in the remediation of polluted soils will be examined, as well

A conceptual phenanthrene bioavailability model applied to rhizosphere environment

A conceptual model is proposed that describes the phenanthrene bioavailability in soil. The model describes the substrate behaviour as resulting from four different processes: sorption-desorption equilibrium, slow diffusion (aged fraction), fast irreversible sorption (bound residues) and biodegradation of the bioavailable fraction. The sorption to soil surfaces is described assuming a rapid rate of sorption-desorption to and from soil surfaces and a slower rate of diffusion into the internal matrix (aging). Biodegradation is described as resulting from bacterial growth using sigmoidal Monod kinetics for the contaminant dissolved in soil solution and first order kinetics for the degradation of the sorbed-available fraction. Sorption and diffusion are approximated by first order kinetics. Finally, the formation of bound residues is described using an exponential saturation equation. The model was evaluated using phenanthrene bioavailability and aging data obtained with cyclodextrines and methanol extractions in sterilised and non sterilised soil microcosms. Monod kinetics parameters were estimated using microbial growth and biodegradation data