Biodegradation of Printed Circuit Boards by Pseudomonas aeruginosa and Achromobacter sp. Isolated from E-Waste Contaminated Soil

Printed circuit boards (PCBs) are basic parts of electronic goods. Their recycling has attracted worldwide attention due to their ever-increasing production, poor environmental safety, and recovery value. The current study aims to evaluate the ecological treatment of PCBs by bacteria indigenous to e-waste-contaminated soils. Bacterial cultures were isolated using a chemically defined medium containing PCBs pieces as the sole carbon source. Phenotypic characterization and partial 16S rRNA gene sequencing of isolates HB3 and HB4 supported their identification as Pseudomonas aeruginosa and Achromobacter sp., respectively. At pH 7, the P. aeruginosa strain caused stronger PCBs degradation (weight loss almost 8%) than Achromobacter sp., while at pH 11 Achromobacter sp. was dominant leading to a 42% weight loss. Surface modifications of the treated PCBs were demonstrated by scanning electron microscopy images showing cracks and fissures. Energy-dispersive X-ray analysis indicated the presence of magnesium, aluminum, silica, calcium, titanium and copper as additional elements on the surface of the treated PCBs. Further, fourier transform infrared spectroscopy analysis suggested the presence of the O–H band (3678.1 cm–1), benzene rings (1601.07 cm–1) and C–H bonds (883 cm–1) in bacterial-treated PCBs. This study highlights the ability of indigenous soil bacteria to degrade PCBs without pre-treatment steps.