Role of microbes in the bioremediation of hydrocarbons, pesticides and municipal wastes

With the rapid explosion of industrialization and human population, the levels of pollutants in the environment have become alarmingly high. Many of these persist in the biosphere for a long period of time and cannot be degraded by physico-chemical methods. Microbes with their nutritional diversity can metabolize a vast range of substrates; thus, microbial degradation has been explored for the purpose of reducing the levels of these persistent pollutants. In general, microbial degradation is preferred because it uses the inherent ability of the microbes to metabolize toxic compounds and hence is cost-effective as well as eco-friendly. The microbes involved are mostly bacteria and fungi from marine and soil environment. It is important to understand the physiology and biochemistry of the microbes as well as microbial consortia involved in order to optimize the process of bioremediation. In this review, we discuss the three major categories of pollutants, viz., hydrocarbons from petrochemical industries, pesticides and municipal wastes including solid wastes and wastewater. For each of these areas of microbial degradation, we discuss the different kinds of wastes generated, limitation of physico-chemical methods, the microbial species or consortium involved in the degradation, insight into the mode of action or mechanisms of enzymatic breakdown and the factors affecting the efficiency of the microbes.