CHROMIUM BIOACCUMULATION POTENTIAL OF BACILLUS CEREUS ISOLATED FROM RHIZOSPHERES OF TAGETES MINUTA L. KULSOOM

Two metal resistant Bacillus cereus strains (AVP12 and NC7401) isolated from metal polluted and nonpolluted rhizospheres of Tagetes minuta were examined for Cr(VI) bioaccumulation potential. It was found that the strains have potential to survive even at metal concentration of 300 mg/l. The per cent removal capacity of Cr(VI) by AVP12 and NC7401 strains was analyzed as a function of environmental factors including pH, incubation time and biosorbate concentration. The optimum pH was found to be 5 andwas selected for further studies. Both Langmuir and Freundlich isotherm models were found suitable for description of Cr(VI) bioaccumulation. The maximum Cr(VI) bioaccumulation capacity by Bacillus cereus AVP12 and Bacillus cereus NC7401 strains isolated from polluted rhizosphere was 181.0 and 107.5 mg/l, respectively while maximum Cr(VI) bioaccumulation capacity by Bacillus cereus AVP12 and Bacillus cereus NC7401 strains isolated from non-polluted rhizosphere was 92.59 and 62.11 mg/l, respectively. Both types of rhizobacterial strains, especially isolated from metal polluted rhizospheres could serve as economical and ecofriendly bioaccumulating agents for removal of Cr(VI). Introduction The contamination of environment by the heavy metals has become a serious threat to the present world due to toxicity, less solubility in biota, indefinitely persistent and non-degradable nature of the heavy metals (Watson et al. 2016). The urbanization and extensive development of the industries increased the discharge level of the toxic heavy metals into the environment. The toxic heavy metals discharge into the environment contaminated the natural water resources including surface as well as ground water and soil; subsequently these toxic heavy metals enter into the food chain (Förstner and Wittmann 2012). Cr(VI) is one of the highly toxic and industrially originated heavy metals which enters into the environment from the unregulated disposal of Cr(VI) containing effluents by several industries including leather tanning, chrome plating, alloy manufacturing and dye producing industries (Nzeve 2015). Cr(VI) causes serious pathological changes in liver, lungs and kidneys. It also causes respiratory inflammation, bronchial spasm, anaphylactic reactions and lungs cancer. Chronic exposure to Cr(VI) causes perforation in nose septum (Tou et al. 2017). Though, various techniques have been developed for the removal of Cr(VI) from the environment but these techniques are expensive, high energy demanding and generate toxic sludge (Cieślik et al. 2015). Bioaccumulation including the use of bacteria and other microbes is an alternative, which is eco-friendly, cost effective and efficient biological method for removal of the toxic heavy metals (Thakur et al. 2016). The high population of bacteria is present in the rhizospheres with great diversity and activity. These rhizobacteria have *Author for correspondence: <zainulabdinchm@gmail.com>. Department of Chemistry, Mirpur University of Science and Technology, Mirpur 10250, Pakistan. Department of Zoology, University of Azad Jammu and Kashmir, Muzaffarabad-13100, Pakistan.