Abstract
The present study aims to address the problem of chromium (Cr) toxicity by providing important insights into the mechanisms involved in its bioremediation. Among the 22 Rhizobium and Sinorhizobium isolates obtained from Sesbania sesban root nodules, Sinorhizobium sp. SAR1 (JX174035.1) tolerated the maximum Cr concentration (1mM) and hence was used for further studies. The excess secretion of extra polymeric substances, as seen from scanning electron micrographs, could be a probable mechanism of adaptation to the Cr stress. The Energy dispersive X-ray spectroscopy data did not show any peaks of Cr. The biosorption studies done on the isolate gave maximum adsorption capacity as 285.71mg/g. The isotherm studies showed a better fit to Langmuir isotherm. The Weber and Morris plot established that the phenomenon of adsorption was governed by film diffusion mechanism. The FTIR analysis suggested the role of cell wall components and extracellular polymeric substances in Cr adsorption to the biomass of Sinorhizobium. On the basis of these results a compiled mechanism of Cr (VI) adsorption and its biotransformation into Cr (III) by Sinorhizobium sp. SAR1 is explained. This work outlines a comprehensive detail for the exact phenomenon of Cr biotransformation by Sinorhizobium sp. SAR1. These results may further help in developing and enhancing effective bioremediation approaches.
Highlights
Human activities have proven to immensely compromise the harmony that existed between him and his environment
The present study aims to address the problem of chromium (Cr) toxicity by providing important insights into the mechanisms involved in its bioremediation
Twenty-two isolates of Rhizobium and Sinorhizobium obtained from root nodules of Sesbania sesban from industrial areas of Navi Mumbai were used for this study [17]
Summary
Human activities have proven to immensely compromise the harmony that existed between him and his environment. Metals are useful in all walks of human life. The past century has witnessed concerning levels of heavy metal contamination. Among the toxic heavy metals, chromium (Cr) is being focused, since it finds a wide range of application in the industrial production of steel, metal alloys, cement, galvanized plastic, leather, paints, fertilizers and fungicides [1]. Tanneries are one of the major contributors to excessive Cr in the environment. They generate around 40 million tons of Cr contaminated wastes [2]. Studies have revealed severe contamination of productive agricultural land and water bodies by tannery waste disposal in developing (i.e. India, Bangladesh) as well as developed (i.e. Australia) countries [3, 4]
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