Heavy metal tolerance and organic compounds utilization in Escherichia species originated from wastewater

Abstract

Environmental pollution is a main concern of the society nowadays. Removal of hazardous pollutants is important to reduce the ecological, social and economic loss caused by the direct discharge of waste into environment. The aims of this study were to analyze the potential of Escherichia sp. previously isolated from wastewater for their tolerance towards heavy metals such as cobalt, zinc, copper, manganese and aluminium and its ability to utilize the selected organic compounds like glucose, glycerol, benzene, kerosene, sulfanilic acid and casamino acid as a sole carbon or/and nitrogen source for growth. The heavy metals tolerance analysis and carbon or/and nitrogen utilization tests on Escherichia sp. were conducted at 37ºC by measuring the absorbance (OD600nm). The results obtained for heavy metals tolerance suggested that this bacterium can tolerate well against both zinc and copper concentrations up to 100mg/L and manganese up to 500mg/L. This strain exhibited intolerance against cobalt and aluminium concentrations starting from 60mg/L and 400mg/L respectively. Based on the carbon utilization tests, highest growth (OD600nm=0.695) was observed in glycerol containing medium. When kerosene, benzene and sulfanilic acid was supplied as the sole carbon source in medium, no growth was observed. The maximum growth (OD600nm) of Escherichia sp. in casamino acid as sole nitrogen source and the sole carbon and nitrogen source are 0.282 and 0.168 respectively. Compared to the sulfanilic acid (SA as sole nitrogen source: OD600nm=0.120), casamino acid was found to be a better sole nitrogen source to promote the growth of Escherichia sp.. Based on the 16S rRNA analysis results, this bacterial strain was identified and confirmed as Escherichia coli with closed identity to E.coli strain LY180. In summary, the Escherichia sp. isolated from wastewater could be potentially used in treatment of wastewater containing heavy metals, proteinaceous and organic compounds in future.