Removal of fluoride in aqueous medium under the optimum conditions through intracellular accumulation in Bacillus flexus (PN4)

The removal of fluoride is essential for water contaminated with fluoride before being utilized since the unsafe concentration of fluoride with respect to the permissible limits. In the present study, there are 61 bacterial strains belonging to fluoride tolerance were isolated from the contaminated soil of Dharmapuri District, Tamil Nadu, India and they were evaluated for different characterization. Among the strains isolated, the strain PN4 showed a high tolerance to fluoride ranging from 500 to 2500 ppm under different stress conditions. The strain PN4 was selected as a possible organism for the degradation and removal of fluoride in an aqueous medium. Based on the morphology, biochemical characteristics and the 16S rRNA sequencing, the bacterium PN4 was identified as Bacillus flexus. In batch mode studies, the glucose was showed the maximum removal of fluoride (86%) followed by beef extract (82%) and a significant level of defluoridation was observed at pH 7.0 and the temperature at 35°C. In the antibiotic-resistance pattern, the strain Bacillus flexus PN4 was shown sensitive to three different antibiotics. Intracellular accumulation of fluoride by the bacterial cell was characterized by SEM- EDAX, TEM and FTIR analysis.