Abstract
Cadmium and zinc are leading heavy metal pollutants causing serious health problems when discharged into the aquatic environments. The present investigation focused on the bioaccumulation of Cd2+ and Zn2+ depending on the sorption process by Bacillus amyloliquefaciens HM28. The selected bacterium was multi-metal (Zn2+, Pb2+, Cd2+, Cu2+ and Li+) and antibiotic ( cefotaxime, ampicilin, nalidixic acid, ceftazidime, penicillin and kanamycin) resistance was resolved. The identified strain showed maximum resistance onCd(2+) (2575 ppm) and Zn2+ (1300 ppm). The sorption of Cd2+ and Zn2+ by a dried bacterium was investigated. Biosorption of Cd2+ was maximum (98.4 +/- 5.2%) at 100 mg/L concentration and maximum Zn2+ (98.3 +/- 1.5%) was detected in the medium containing 150 mg/L metal ion. Bioremoval was maximum after 30 min contact time with dried biomass and the absorption rate improved. The optimum Cd2+ and Zn2+ bioremoval yield of 93 +/- 4.4% and 89.8 +/- 4.3% were observed, at pH 7.0 and 7.5, respectively. Despite the significant reduction in growth rate, heavy metals increased nitro-blue tetrazolium reduction from 11 +/- 1.3 to 67 +/- 3.3%. Dehydrogenase activity elevated due to heavy metal stress. Bacterial biomass was immobilized in a glass column (20 cm x 2 cm). Biosorption of Cd2+ and Zn2+ ions were performed in a packed bed column. The breakthrough time of Cd2+ was 210 min at 1 mL/min flow rate and it decreased 94 min at 5 mL/min flow rate, whereas 240 min at 1 mL/min, and 90 min at 5 mL/min, respectively. The absorption capacity was 4.87 +/- 0.8 to 5.43 +/- 0.5 mg/g for Cd2+ and 3.85 +/- 0.3 to 4.53 +/- 0.4 mg/g for Zn2+. The present findings revealed the potential of B. amyloliquefaciens HM28 biomass in Cd2+ and Zn2+ biosorption, with feasibility in the bioremediation of Cd2+ and Zn2+ contaminated water. (C) 2021 Elsevier Ltd. All rights reserved.