Biodegradation OF Xenobiotics .
Microorganisms play an important role in the removal of synthetic organic compounds from the environment. This chapter gives an overview of the evolution of biodegradation pathways and describes the strategies that microorganisms have evolved to transform important molecular structures. The actual effectiveness of biodegradation in the environment is determined by the bioavailability of the compounds. As a general rule, one could state that the release rates of synthetic compounds should not exceed the environment’s ability to degrade them. Biodegradation:
Certain microbes on continuous exposure to xenobiotics develop the ability to degrade the same as a result of mutations. Mutations resulted in modification of gene of microbes so that the active site of enzymes is modified to show increased affinity to xenobiotics. Xenobiotics are any chemical compounds that are found in a living organism, but which are foreign to that organism, in the sense that it does not normally produce the compound or consume it as part of its diet. For example, in humans, most drugs are part of this category, since people don't produce them naturally, or consume them under normal circumstances.
Xenobiotic compounds, owing to its recalcitrant nature, is hard to break down and degrade. The complexity of its chemical composition adds to this. For breaking down such compounds the enzymes act on certain groups present in the compound. For eg: in the halocarbons the halogen group is targeted. Enzymes like oxygenases play a major role. The bonds like ester-, amide-, or ether bonds present in the compounds are first attacked leading to breaking down of compounds. In some cases the aliphatic chains and in aromatic compounds the aromatic components may be targeted. The site and mode of attack depends on the action of enzyme, its concentration and the favourable...
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