Lead biotransformation potential of allochthonous Bacillus sp. SKK11 with sesame oil cake in mine soil

Authors: GOVARTHANAN, MUTHUSAMY - Chonbuk National University; CHO, MIN - Chonbuk National University; LEE, KUI-JAE - Chonbuk National University; PARK, YOOL-JIN - Chonbuk National University; MYUNG, HYUN - Chonbuk National University; KRISHNAMOORTHY, R - University Of Madras; LEE, SANG-HYUN - Chonbuk National University; Lovanh, Nanh; KAMALA-KANNAN, SERALATHAN - Chonbuk National University; OH, BYUNG-TAEK - Chonbuk National University

Submitted to: The Royal Society of Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/15/2015
Publication Date: 7/17/2015
Citation: Govarthanan, M., Cho, M., Lee, K., Park, Y., Myung, H., Krishnamoorthy, R.R., Lee, S., Lovanh, N.C., Kamala-Kannan, S., Oh, B. 2015. Lead biotransformation potential of allochthonous Bacillus sp. SKK11 with sesame oil cake in mine soil. The Royal Society of Chemistry. 5:54564-54570.

Interpretive Summary: Heavy metal contamination poses a serious threat to both environment and human health. Rapid industrialization, mining activities, disposal of metal wastes, usage of pesticides, and spillage of petrochemicals are the major source of heavy metal pollution in the ecosystem and agricultural lands. Elimination of heavy metals from the contaminated soil is particularly challenging as these metals are non-biodegradable. Among the heavy metals, lead (Pb) has been recognized as one of the most hazardous pollutant in the environment. Moreover, Pb is not an essential nutrient in metabolic processes of plants and/or animals, and they can accumulate to high levels which can cause toxicity to organisms. Thus, development of remediation strategies for heavy metals polluted soils is important for ecological conservation and human health. Biotransformation is an efficient selective bioremediation technology utilizing the potential of heavy metal resistant microorganisms to transform metal ions. A number of micro-organisms inhabiting soil and water can transform active fraction of metals into inactive fractions, which diminishes the bioavailability and biomagnifications of metals in the food chain. Therefore, the objective of this study was to isolate and characterize Pb resistant bacteria from polluted mine drainage soil and biostimulate of these resistant bacterial activity using agricultural by-products such as sesame oil cake for sustainability. The results show that application of sesame oil cake extract enhanced the bacterial activity in mine drainage soils. Total Pb (about 39%) was successfully transformed in mine drainage soils with sesame oil cake extract amendment. The utilization of oil cake extract not only increased the transformation rate but also improved the soil metabolic activity, as illustrated by the extracelluar enzymes in bioremediated mine soils. The present study provides a potential eco-friendly and sustained way for enhanced transformation of Pb and other heavy metal contaminants from mine drainage soils and as well as from contaminated agricultural lands.

Technical Abstract: This study was aimed at assessing the potential of allochthonous Bacillus sp. SKK11 and sesame oil cake extract for transformation of Pb in mine soil. The bacteria were isolated from a brackish environment and identified as Bacillus sp. based on partial 16S rDNA sequences. The isolate SKK11 exhibited maximum resistance to Pb (750 mg/L). Growth kinetic studies revealed that presence of oil cake extract (2%) extended the log phase of the isolate SKK11. Transmission electron microscopy and X-ray diffraction studies showed that isolate SKK11 transformed Pb either intracellularly or extracellularly. Selective sequential extraction studies showed that the bioremediation decreased the exchangeable fraction (24.9%) and increased the residual fraction (21.2%) of Pb in mine soil. X-ray diffractogram of bioremediated soil showed a major decrease (79.0%) in the intensity of the plagioclase mineral peak. Urease, dehydrogenase, amylase, invertase, cellulase, and alkaline phosphatase enzyme activities were increased in bioremediated mine soil. Obtained results point out that isolate Bacillus sp. SKK11 and sesame oil cake extract could potentially be used for the transformation of Pb in contaminated soil.