Metals naturally exist in the crust of the earth, and their compositions vary among different localities, resulting in structural disparity of surrounding concentrations. Some heavy metals are much important in trace amounts in respect to living organisms related to their metabolic activities. High solubility of various heavy metals changes them into extremely toxic and perilous contaminant of water and soil when discharged by many industrial activities. When these metals are released into the environment, they can be leached into the underground waters, depositing in the aquifers, or run off into surface waters and soils thereby resulting in water and soil pollution. Thus, heavy metals become a potential contaminant for environment that can partake in trophic transfer in food chains. The toxicity of heavy metals mainly depends upon its relative oxidation state, which is responsible for physiological bio-toxic effects. When these metals enter into the living organisms, they, combine with proteins, enzymes, and DNA molecules, form highly stable biotoxic compounds, thus altering their proper functioning and obstructing them from the bioreactions. Arsenic, chromium, cadmium, and lead are highly toxic and produce mutagenic, carcinogenic, and genotoxic effects. Hence, this chapter is focused on occurrence and allocation of heavy metals, their toxicological impact on environment, and their possible eco-friendly remedies for green and healthy environment.

The bioremediation process of industrial waste can be made more efficient using ligninolytic laccase enzymes, which are obtained from fungi, bacteria, higher plants, insects, and also in lichen. Laccase are catalyzed in the mono-electronic oxidation of a substrate from the expenditure of molecular oxygen. This enzyme belongs to the multicopper oxidases and participates in the cross linking of monomers, involved in the degradation of wide range industrial pollutants. In recent years, these enzymes have gained application in pulp and paper, textile and food industries. There are numerous reviews on laccases; however, a lot of information is still unknown due to their broad range of functions and applications. In this review, the bacterial laccases are focused for the bioremediation of various industrial pollutants. A brief description on structural molecular and physicochemical properties has been made. Moreover, the mechanism by which the reaction is catalyzed, the physical basis of thermostability and enantioselectivity, which requires more attention from researchers, and applications of laccase in various fields of biotechnology are pointed out.

No abstract