Introduction

Industrial revolution has resulted in many materials which are man-made and not resembling to natural ones. The term xenobiotic(stranger to life) is derived from the Greek word 'xenon' - a strange and 'bios' - life. For the environmental chemist, xenobiotic implies foreign to the biosphere. Anthropogenic is a specific term for man-made. These materials may be products, intermediates or wastes of our industrial and other activities. And at whatever stage they enter into nature, they can not become a part of cycle of matter. This is for the simple reason that microorganisms do not find any resemblance between these materials and their natural food habits. However simultaneously it is also true that all foreign to nature man-made substances need not be non-degradable.Those compounds which are not degraded in nature following their release into environment even when the conditions appear to be adequate for microbial growth, are termed as. Recalcitrant compounds persist in all natural environments regardless of whether they are inherently biodegradable or not. Without being bias to any industry, it is well accepted fact that xenobiotic compounds, toxic chemicals, hazardous wastes come from the petrochemical industry, pesticide industry, chemical industry, mining, metal processing etc. The list of pollutants which pose environmental and health hazard and are tough for biodegradation is long one and includes solvents, wood preservative chemicals, plasticizers, refrigerants, coaltar wastes, pesticides, biphenyls, polychlorinated and polybrominated biphenyls, synthetic fibers, plastics, polyvinyl chloride, polystyrene, detergents like alkyl-benzene sulphonates, oils etc