Prolonged consumption of fluoride-contaminated water poses health problems like dental and skeletal fluorosis in many parts of the world including India. In regions with acute water scarcity, it demands immediate intervention like de-fluoridation of water before consumption. In the current study, fluoride-resistant bacteria were isolated from fluoride-contaminated groundwater and soil samples collected from Dungarpur district, India, for their potential use in defluoridation. Out of a total of 53 bacterial isolates that were recovered and screened for fluoride resistance, three highly fluoride-resistant isolates DWC1, DWC2 and DWB5, resistant to up to 9200 mg L-1, 7200 mg L-1 and 5200 mg L-1 fluoride respectively, were characterized and identified as Aeromonas sp., Brevibacterium sp. and Paenibacillus sp. respectively. The fluoride removal capacity of isolates DWC1, DWC2, DWB5 and a consortium of all the three isolates was found to be 68.7%, 73.4%, 76.7 % and 70.1% respectively on nutrient broth supplemented with NaF (2000 mg L-1) after 8 days of incubation. Defluoridation conditions for the strain showing the best result (Paenibacillus sp.) were optimized for real fluoride-rich water collected from Ajmer District, India, using the Taguchi design of experiment. A defluoridation of up to 73.3% was observed at 40 °C temperature and pH 8 with inoculum: water ratio of 2:1 after 8 days of incubation. To the best of our knowledge, the defluoridation capacity of Paenibacillus sp. is the highest reported in literature to date for real water samples and could be investigated in further detail for commercial application.
Keywords: Energy dispersive X-ray (EDX); Fluoride-resistant bacteria; Fluorosis; Paenibacillus; SPADNS.