Biotransformation potential of hexavalent chromium by Bacillus pumilus-S4, Pseudomonas doudoroffii-S5 and Exiguobacterium-S8 in association with hydrophytes

Abstract

Three chromium-resistant bacteria Bacillus pumilus-S4, Pseudomonas doudoroffii-S5 and Exiguobacterium-S8 were isolated from chromium-contaminated wastewater/soil and could resist very high concentrations of potassium chromate in Luria agar (up to 25 mg ml -1 ) and acetate minimal medium (2 mg ml -1 ). The strains showed growth at diverse pH and temperatures and could resist multiple heavy metals. Pseudomonas doudoroffii-S5 reduced (8.27 mg hexavalent chromium 24 h -1 ) at a lower initial potassium chromate concentration (100 lg ml -1 ), but overall more chromate (28.4 mg hexavalent chromium 24 h -1 ) was reduced at a higher initial concentration (1,000 lg ml -1 ). The addition of various heavy metals (zinc sulphate, copper sulphate, and manganese sulphate at 50 lg ml -1 ) in the chromium reduction media did not significantly affect the hexavalent chromium reduction potential of these isolates. The chromium removal/detoxification potential of these strains increased when used in conjunction with hydrophytes Eichornia crassipes and Pistia stratiotes. Interestingly, the whole process runs automatically with less energy input, that is, the bacterial strains support the growth of plant while in turn the plant releases exudates that help bacterial growth.

Recent bioreduction of hexavalent chromium in wastewater treatment: A review

“…Desorption indicated the removal of Cr(VI) due to reduction reaction instead of biosorption. [81] Similar works report using different isolated strains with variation of pH, temperature and initial concentration of Cr(VI) [82,83].…”