Heavy metal tolerance of lysinibacillus fusiformis ZB2 isolated from textile effluent

Abstract

Heavy metal pollution has always been considered as one of the major threats to the environment and human health since these metals can accumulate in the food chain, inactivate cellular enzymes and may cause cancer related diseases. Conventional physiochemical methods do not provide economical treatment for the removal of heavy metals from heavy metal polluted environment. An effective and economical alternative method that has been widely reported is microbial bioremediation. In this study, the minimal inhibitory concentration (MIC) of Lysinibacillus fusiformis ZB2 for selected heavy metals, namely, cadmium (Cd), zinc (Zn), lead (Pb) and chromium (Cr(VI)) were determined. This bacteria was isolated previously from the textile effluent. It was grown in low phosphate medium (LPM) with glucose and tryptone as its carbon and nitrogen source respectively. L. fusiformis ZB2 reached its exponential growth within 48 hours of incubation in the LPM. The MIC of the bacteria for Cd, Zn, Pb and Cr(VI) were determined in solid and liquid media. The MIC obtained was relatively higher when using the liquid media. The MIC for Cd, Zn, Pb and Cr(VI) were 25, 75, 150, and 3500 ppm, respectively as compared to using the solid media MIC for Cd, Zn, Pb and Cr(VI) were 10, 75, 250, 3000 ppm, respectively. The order of toxicity of heavy metals towards Lysinibacillus fusiformis ZB2 was Cd>Zn>Pb>Cr(VI). The bacteria was found to be tolerant towards Zn, Pb and Cr(VI) with maximum tolerance towards Cr(VI).