Bioleaching of valuable metals from printed circuit boards (PCBs) using <i>Enterobacter quasihormaechei</i> isolated from E-waste

The current study employed the isolation of a novel metal-resistant bacterium, <i>Enterobacter quasihormaechei</i> (GenBank Accession No. OR659321) from raw printed circuit boards (PCBs) waste for its bioleaching potential. The bacterium shows promising recovery efficiencies of multiple important metals (Ag 87.5%, Al 60.53%, Mg 58.71%, Cr 56.52%, Ca 55.80%, Cu 55.03%, Mo 50%, Zn 46.36%, Ba 44.22%, Fe 34.54%, Ni 34.15% and Mn 28.22%) from PCBs waste at 37 °C, 150 rpm and 5-days of incubation period. Further confirmation of bioleaching was carried out by FTIR, FE-SEM, EDS and XRD, respectively. The oxidation-reduction potential (ORP) was also investigated, and it was found to be reduced during the bioleaching of electronic waste. Overall, the current study demonstrates that the bacterium, <i>E. quasihormaechei</i>, can recover multiple valuable metals from PCBs without chemical pretreatment or nutrient additives through eco-friendly and cost-effective bioleaching methods.