Assessment of plastic degradation by indigenous bacteria from waste disposal sites

Abstract

The present study focuses on the isolation of bacterial pathogens from waste disposal sites, and examination of their efficiencies for degrading various plastics. Seven bacterial isolates such as E. coli, Corynebacterium spp., Micrococcus spp., Azotobacter spp., Pseudomonas spp., Staphylococcus spp., and Bacillus spp. were identified. Bacillus spp. exhibited the highest percentage reduction in black plastic weight (47.46 %), while Corynebacterium spp., and E. coli achieved a maximum reduction of 45.76 and 46.42 % for pink plastic respectively. Pseudomonas spp. and Micrococcus spp. demonstrated notable reductions of 46.43 % and 56.60 % in white and Canteen Stores Department (CSD) biodegradable plastics, respectively. Optical density (OD) measurements revealed that bacterial isolates achieved maximum OD values with CSD plastics, emphasizing their proficiency in plastic degradation. Fourier Transform Infrared Spectroscopy (FTIR) confirmed the degradation process, with a decrease in the peak value from 2916 to 2914 cm⁻1 for pink plastic, signifying alkane, and alkene presence. Three new peaks at 1398, 1371, and 1361 cm⁻1 in the FTIR spectrum of CSD plastic indicated presence of alcohol. Scanning Electron Microscopic (SEM) micrographs illustrated bacterial colonization, cracks, and spots on plastic surfaces, while X-ray Diffraction (XRD) spectra showed peaks at 4.083, 3.705, 3.020, and 1.909, suggesting plastic degradation. In conclusion, soil of waste disposal site harbored diverse microbial species, and have highlighted their effectiveness in mitigating environmental pollution by degrading hazardous plastic waste.

Keywords

• Plastic degradation
• Bacterial isolates
• Waste disposal sites
• Fourier transform infrared spectroscopy
• Scanning electron microscopy
• X-ray diffraction