Defluoridation Efficiency of a Novel Fluoride-Resistant Exiguobacterium indicum MLN15

Fluoride contamination of groundwater poses a global threat to humans. The current study focused on the defluoridation efficacy of a fluoride-resistant bacterium, isolated from fluoride-contaminated areas of Birbhum district, West Bengal, India. Strain MLN15 was able to tolerate a maximum fluoride concentration of 3500 mgL −1 . Based on morphological, biochemical, and 16S rDNA gene sequence, strain MLN15 was identified as Exiguobacterium indicum MLN15. Optimal growth conditions were observed at pH 7, temperature 35˚C, and 0.5 molar NaCl. The selected strain also showed maximum defluoridation efficiency of 53.5% at optimal growth conditions of 24 h incubation. In addition, fluoride adsorption on bacterial cell surfaces was confirmed using SEM, SEM–EDX, and TEM analyses. All the results indicate that the bacterial strain Exiguobacterium indicum MLN15 could be a potential organism for fluoride-bioremediation.