Isolation and Characterization of Bacillus licheniformis Strain for Bioleaching of Heavy Metals

Increased usage and improper management of electronic wastes result in immense environmental pollution. Although conventional techniques are well known for heavy metals removal from the environment, their high cost and severe environmental consequences indicate the urgent requirement of cost-effective methods of heavy metals uptake. Bioaccumulation can be considered as an alternative to the traditional methods in terms of their cost-effectiveness and maximum recovery of the metal ions. This study deals with the isolation of heavy metals tolerant Gram-positive bacterial strain, Bacillus licheniformis JAJ3, and its application in bioaccumulation of copper, lead, and nickel and bioleaching of heavy metals from electronic waste. 16S rRNA sequencing was performed to identify the bacterial strain. The accumulation study was carried out in a liquid medium and analyzed using atomic absorption spectroscopy. Bioleaching activity was checked using the one-step procedure. For bioleaching studies of heavy metals, printed circuit boards (PCBs) were used as a source of electronic wastes. Scanning electron microscopy and energy dispersive spectroscopy were used to record the changes before and after experimental procedures. The organism was able to accumulate 98.6% copper, 64.6% lead, and 57.3% nickel. The bioaccumulation reaction followed pseudo-second order kinetics model (R2 value 0.92, 0.92, 0.99 for copper, lead, and nickel bioaccumulation respectively). Efficient bioleaching activity was shown by the strain. The experimental analyses confirmed that the strain is efficient in the bioleaching of heavy metals from electronic wastes and thus can be used in management of the electronic wastes.