Bioleaching of Heavy Metals by Streptomyces avermitilis - BBA4 Isolate from Coal Mine Soil of Tamil Nadu.

Abstract

Printed Circuit Board (PCB) includes precious metals, heavy metals and brominated flame retardants. The usage of PCB is increasing exponentially, generated in vast quantities, and considered an E-waste contaminating the environment. The bioleaching potential of a novel isolated Streptomyces BBA4 strain from a coal mine soil was studied and discussed here. A total of twelve isolates were isolated from coal mine soil (Neyveli area). The metal-resistant activity of the isolated cultures was examined using a dot plot and agar well diffusion assay. Both assays revealed that the isolate BBA4 showed resistance and survival ability in the copper (Cu) and chromium (Cr)-rich environment up to 1000mg/kg and in the iron (Fe) and silver (Ag)-rich environment up to 500mg/kg, respectively. Based on the phenotypic, physiological, biochemical and molecular characteristics, the novel and potential strain (BBA4) isolated from coal mine soil matched with Streptomyces avermitilis. The strain showed bioleaching ability to recover 73.3% Cobalt and 36.4% Chromium within 120h under pH 5 (in vitro conditions) from the PCB. The heavy metal content in the PCB was analyzed using quantitative analytical techniques, such as Atomic Absorption Spectroscopy (AAS) and Powder X-ray diffraction (XRD). The analysis of XRD peaks exhibited an increase in crystallinity with the Cr, associated with the accumulation of Cr in the bioleached residues. Thus, generated data from this investigation reveal that BBA4 is an effective bioleaching strain on PCB over other environmentally hazardous chemical leaching methods.