Biodegradation of high-density polyethylene (HDPE) using bacterial strains isolated from fresh bovine feces

High-density polyethylene (HDPE) significantly contributes to persistent environmental degradation due to its non-biodegradability and widespread usage. Bioremediation of plastic-contaminated sites by ubiquitous microbial agents appears to be an effective and safe alternative method for plastic waste disposal. This study investigated HDPE degradation by Brevibacillus parabrevis EVB 2 and Bacillus velezensis EVB8, isolated from cow fecal samples. The biodegradation test was assessed through colony-forming unit (CFU) counting, pH variation, residual weight loss (%), CO₂ emission measurements at 10-day intervals, and structural analysis using scanning electron microscopy (SEM), attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy, X-ray diffraction (XRD), and Gas chromatography-mass spectrometry (GC-MS). EVB2 and EVB8 decreased the weight of HDPE films by 3.78 ± 0.90% and 1.84 ± 0.75%, respectively. Statistical analysis indicated that both reductions were significant compared to the control (p ≤ 0.05), with EVB2 showing the greatest weight loss and producing the highest CO₂ emission (104.42 ± 9.50 mg). SEM analysis indicated surface alterations in the treated films, including cracks and erosion, further validating the degradation by chemical changes and crystallinity levels detected through FTIR, XRD, and GC-MS analysis. This study demonstrates that the tested bacterial strains can achieve measurable HDPE biodegradation within 40 days without prior abiotic treatment, offering an efficient approach compared to previous studies that required pre-treatment or extended incubation periods. This work highlights the capacity of these strains to serve as effective microbial agents for HDPE biodegradation, supporting their application in the long term for sustainable plastic waste management.