Sustainable Biodegradation of Recalcitrant HDPE Plastics using Bacillus pseudomycoides: A Microbial Approach towards Plastic Waste Mitigation

High Density Polyethylene (HDPE) plastic is one of the most resistant manmade polymers,
posing significant environmental challenges. In this study, microbes capable of growing on this
recalcitrant plastic were isolated from soil samples collected from plastic contaminated areas. The
isolated Bacillus pseudomycoides utilized High-Density Polyethylene (HDPE) of 75 microns as the sole
carbon source under controlled conditions (neutral pH; temperature: 30 - 37°C) for growth.
Biosurfactant production by Bacillus pseudomycoides was confirmed, and its cell surface
hydrophobicity was measured via BATH assay. The efficacy of biodegradation was assessed by
Gravimetry, SEM, FTIR and GC-MS. Gravimetric analysis showed a significant weight loss of 31% in the
HDPE plastics after one year by Bacillus pseudomycoides when compared to the control in similar
conditions without any microbes. Scanning Electron Micrographs showed bacterial adherence and
fissures on HDPE surface, indicating degradation. FTIR showed major changes in polymer structure, such as appearance of hydroxyl (-OH), carbonyl (C=O), and alkane/alkene groups and possible
synthesis of carboxylic acids, in consistence with microbial fermentation. GC MS analysis showed the
presence of diverse HDPE degradation products. Control samples indicated no significant changes,
ruling out any abiotic factor influence. These results demonstrate Bacillus pseudomycoides has the
ability to degrade HDPE plastics.