Industrialization is a hallmark of civilization but nowadays it is becoming matter of great concern. Industrial emissions unfavorably affect the environment, leading to the large-scale worldwide destruction of agricultural land along with water bodies (1, 2). Various toxic substances are released that accumulate in the environment and food chains, thereby affecting many biological processes. Chromium (Cr) is one the important metal being employed far and wide in numerous industrial processes, including chrome leather tanning, chrome plating, ceramics, dyes, paints and pigments manufacturing, textile processing, metal finishing etc.(3-6). Leather processing industry is one of the major industries utilizing chromium in the form of chrome liqueur or chrome powder. Residual chromium is thus discharged in solid as well as liquid effluent. It exists in various oxidation states ranging from -2 to +6 but the most persistent forms are hexavalent (Cr6+) and trivalent (Cr3+) species. Hexavalent chromium is the most toxic form, mainly available as oxyanions, whereas trivalent chromium is hundred-fold less toxic, less soluble and less mobile, mostly found as oxides, hydroxides or sulfates (7, 8). Hexavalent chromium is a strong oxidizing agent, mutagen and teratogen (4, 9). Its oxyanionic form (CrO42−), analogous in structure to sulfate and phosphate ions, readily permeate through bacterial and eukaryotic cells resulting in intracellular reduction leading to chromate-induced toxicity (4, 8, 10). The presence of chromate in the environment inhibits most microorganisms, but it also promotes the selection of metal resistant bacteria (2, 11).
In Kanpur, about 400 leather processing industries at Jajmau, discharge both liquid as well as solid wastes into canals and rivers with residual chromium. This causes chromium contamination not only of water but also of aquatic lives, land, vegetables, farming and crops, posing great threat to environment and human health. The most direct and severe effect comes out with leather-cut wastes, which are conventionally being processed into feed ingredient (as a protein source). This chromium content thus acts as major source for its migration into the food chain.
Chromium does not degrade completely but can be transformed or removed either through adsorption/accumulation or by physicochemical treatments. Large amount of chemicals as well as energy is used during these processes, therefore unsuitable for execution at large scale (12). Chromium resistant bacteria offer an economical as well as eco-friendly selection for chromate detoxification as well as bioremediation (8, 13). Chromium reduction takes place under both aerobic as well as anaerobic conditions. Numerous bacteria have been reported for reducing/transforming Cr6+ to Cr3+, e.g. Bacillus sp., Escherichia coli, Enterobacter cloacae, Pseudomonas fluorescens, Providencia sp., Exiguobacterium sp. etc. (14-18).
The objective of the present study is to isolate...