Bioleaching of Metals from Printed Circuit Boards by Mesophilic Lysinibacillus sp.

In view of the rapidly increasing e-waste, bioleaching of metals from e-waste is an economical and ecologically conscientious option to address the issue of its disposal and/or recycling. Bioleaching of heavy metals by using bacteria of the Bacillus genus has been reported in many studies; however, the bioleaching potential of the Lysinibacillus genus is unexplored. In the present study, Lysinibacillus sp. SDG4 was isolated, identified, analysed and used for leaching toxic metals from e-waste printed circuit boards (PCBs). The bioleaching of metals was deciphered and analysed by using scanning electron microscopy (SEM) along with energy-dispersive X-ray spectroscopy (EDX), Fourier transform infrared spectroscopy (FTIR) and inductively coupled plasma-optical emission spectrometry (ICP-OES). The presence of organic acids in the Lysinibacillus primary metabolites was established by FTIR analysis. The presence of functional groups like C–O and C–N in the transmittance band range of 1037.70 to 1658.78 cm-1 wavelength, C–H at 2746.63 and 2964.59 cm-1, O–H at 3412.08 cm-1 and RCO–OH at 582.50 cm-1 suggested the production of metal chelating functional groups by the bacterial strain. The heavy metal profile was determined using ICP-OES analysis. This revealed bioleaching of Al (99.74%), Zn (99.60 %), Cu (93.75%) and Fe (59.24%) in 30 days with a PCB concentration of 1 gm/ml by Lysinibacillus sp. SDG4.  These findings confirmed the display of morphological changes by accumulation of metals by Lysinibacillus sp. SDG4 using SEM-EDX analysis. Thus, the study exhibited the potential of the Lysinibacillus genus in bioleaching metals from e-waste.