Biotransformation of chromium (VI) by Bacillus sp. isolated from chromate contaminated landfill site

ABSTRACT

A potent Cr (VI) resistant bacterial strain DHS-12(7) was isolated from tannery waste landfill site and identified as Bacillus sp. based on pheno- and genotypic methods. The maximum tolerable concentration (MTC) of Cr (VI) was found as 1000 and 250 ppm in nutrient-rich and minimal salt medium, respectively while significant variation of MTC and Cr (VI) reduction efficiency was observed in the solid and liquid medium. The complete reduction of 10 and 25 ppm Cr (VI) was recorded within 18 h and 24 h., respectively in the minimal salt medium and the reduction trend of the strain was bacterial growth-associated. The detection of almost invariable total Cr concentration and the presence of NADH-dependent chromate reductase activity in the cell-free extract, indicated the extracellular Cr (VI) reduction rather than intracellular uptake. Furthermore, chromate reductase (ChrR) gene was amplified, sequenced and the translated amino acid sequence of the ChrR gene showed a high degree of homology with chromate reductase of different organisms. Conclusively, the findings of the present study highlight that Bacillus sp. strain DHS-12(7) can be a potent bioremediation agent for detoxification of Cr (VI) from the contaminated environmental sites for ecological restoration.

KEYWORDS:

• Bacillus sp.
• Hexavalent chromium
• Cr (VI) reduction
• chromate reductase
• Bioremediation

Acknowledgement

The study was funded by the Ministry of Science and Technology, Government of the People’s Republic of Bangladesh in the fiscal year of 2016–2017 [Grant No.: 39.00.0000.012.002.005.16/20].The authors would also express their gratitude to the authority of the Agrochemical and Environmental Research Division, Institute of Food and Radiation Biology, Atomic Energy Research Establishment, Bangladesh for providing Atomic Absorption Spectrophotometer (AAS) analysis facility.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Notes on contributors

Mr. Md. Ekramul Karim is a Lecturer at the Department of Microbiology, Faculty of Life and Earth Sciences, Jagannath University, Dhaka, Bangladesh. Before joining academia, he was a scientific officer at the Environmental Biotechnology Division of the National Institute of Biotechnology, Bangladesh (Specialized biotechnology-based research organization under the Ministry of Science and Technology, Bangladesh). His research interests are focused on microbial ecology, environmental pollution and bioremediation.

Dr. Shamima Akhtar Sharmin is a Senior Scientific Officer at the Environmental Biotechnology Division of the National Institute of Biotechnology, Bangladesh. She is interested in environmental pollution and bioremediation research.

Mr. Md. Moniruzzaman is a Scientific Officer at the Molecular Biotechnology Division of the National Institute of Biotechnology, Bangladesh. His research focus is on molecular and cellular biology.

Dr. Zeenath Fardous is a Senior Scientific Officer at the Institute of Food and Radiation Biology of the Atomic Energy Research Establishment, Bangladesh. Her research focus is on environmental chemistry and toxicology.

Mr. Keshob Chandra Das is a Principal Scientific Officer at the Molecular Biotechnology Division of the National Institute of Biotechnology, Bangladesh. He is focused on environmental science and pollution research.

Dr. Subrata Banik is currently working as an Assistant Professor at the Department of Biochemistry and Molecular Biology, Jahangirnagar University, Bangladesh. He was awarded a PhD in Molecular Toxicology from Hokkaido University, Japan. Dr. Banik is interested in the research area of molecular toxicology, nutritional biochemistry and bioremediation.

Dr. Md. Salimullah is a Chief Scientific Officer at the Molecular Biotechnology Division of the National Institute of Biotechnology, Bangladesh. He obtained his PhD from Saitama University, Japan and has excellent research contributions in the Genomics and Transcriptomics field. His current research interest is on the area of molecular and cellular biotechnology, drug design and development.

Additional information

Funding

The study was funded by the Ministry of Science and Technology, Government of the People’s Republic of Bangladesh in the fiscal year of 2016–2017 [grant number: 39.00.0000.012.002.005.16/20].