The is released, its stability in the environment
The ever-growing list of chemical contaminants released into the environment on a large scale includes numerous aliphatic and aromatic compounds, such as petroleum hydrocarbons, halogenated and nitro-aromatic compounds and phthalate esters. These compounds enter the environment through many different paths. As components of fertilizers, pesticides and herbicides, some are distributed by direct application. The local concentration of a contaminant depends on the amount present and the rate at which the compound is released, its stability in the environment under both aerobic and anaerobic conditions, the extent of its dilution in the environment, the mobility of the compound in a particular environment and its rate of biological or non-biological degradation 1.The term “bioremediation” has been used to describe ‘the process of using microorganisms to degrade or remove hazardous components of the wastes from the environment’. Biodegradation and its application in bioremediation of organic pollutants have benefited from the biochemical and molecular studies of microbial processes. Various authors have reviewed the subject of biodegradation of organo-pollutants over the past decade. Biotransformation of organic contaminants in the natural environment has been extensively studied to understand microbial ecology, physiology and evolution for their potential in bioremediation 2. According to Dasand K et al. studied the extensive biodegradation of alkyl aromatics in marine sediments which occurred prior to detectable biodegradation of n-alkane pro?le of the crude oil and the microorganisms, namely, Arthrobacter, Burkholderia, Mycobacterium, Pseudomonas, Sphingomonas, and Rhodococcus were found to be involved for alkyl aromatic degradation. Acinetobacter sp. Was found to be capable of utilizing n-alkanes of chain length C10–C40 as a sole source of carbon 29.Heavy metal, pesticides and petrol contamination in water is recognized as a severe environmental problem and therefore the study related to water contamination and land disposal has become important. These chemical may enter into the water and get disposed in the land such as (a) catechol is also widely used to produce food additive agents, hair dyes, and antioxidants. Due to the lack of information regarding the duration of exposure in the above studies, it is not clear whether these health effects were observed following acute or chronic exposure 11, (b) Endosulfan is one of the insecticides used. The EPA classifies endosulfan in its most extreme toxicity category (highly acutely toxic) because relatively small doses prove lethal 12, (c) carbaryl exposure in humans may also cause eye and skin irritation. Tests involving acute exposure of rats, mice, rabbits, and guinea pigs have demonstrated carbaryl to havemoderate to high acute toxicity from ingestion and moderate acute toxicity from dermal exposure 13, (d) Toluene is added to gasoline, used to produce benzene, and used as a solvent. Exposure to toluene may occur from breathing ambient or indoor air affected by such sources, (e) Xylene is an aromatic hydrocarbon widely used in industry and medical technology as a solvent. EPA has classified mixed xylenes as a Group D, not classifiable as to human carcinogenicity 15, (f) Acrylamide is also used as a flocculent for sewage and waste treatment, soil conditioning agents, ore processing, paper, and in the manufacture of dyes, adhesives and permanent press fabrics. EPA has classified acrylamide as a Group B2, probable human carcinogen 16. Oxygenases are grouped into two categories; the monooxygenases and dioxygenases on the basis of number of oxygen atoms used for oxygenation. They play a key role in the metabolism of organic compounds by increasing their reactivity or water solubility or bringing about cleavage of the aromatic ring. Generally the introduction of O2 atoms into the organic molecule by oxygenase results in cleavage of the aromatic rings. Historically, the most studied enzymes in bioremediation are bacterial mono- or dioxygenases. A detailed study of the role of oxygenases in biodegradation process is available 18. Guzik U et al., proposed that biodegradation process free enzymes often undergo deactivation. They found catechol 1, 2- dioxygenase is highly active enzymes and for that reasons it can be used for industrial scale production. On the other hand, the environments are polluted by a lot of aromatic compounds such as chlorophenols, creosols or nitrophenols which can be substrates for catechol 1, 2- dioxygenase. This free enzyme can undergo deactivation in biodegradation and industrial processes so it is very important to obtain highly stable enzymes 23. In the present study, in-silico approach is used to predict the best potential microorganisms which can degrade vast majority of known pollutants with catechol 1, 2- dioxygenase enzymes as a receptor in different microorganisms involved in bioremediation.