Functional Evaluation of Bacillus subtilis DCP04 from Korean Fermented Soybean Paste: A Potential Probiotic Strain for Polyethylene Degradation and Adsorption

Micro- and nanoplastics (MPs and NPs) are recognized as emerging contaminants posing potential risks to human health. Recent evidence highlights the potential of food-grade microbial strains to bind these particles and facilitate their removal, suggesting a promising probiotic-based strategy for mitigating their adverse health effects. This study investigated the adsorption and biodegradation capabilities of <i>Bacillus subtilis</i> DCP04, a strain isolated from Korean fermented soybean paste, cheonggukjang, on low-density polyethylene (LDPE) particles. Biofilm formation assays and morphological observations confirmed the strain's ability to adhere to the surface of LDPE. Subsequent experiments demonstrated that DCP04 effectively adsorbed LDPE particles in a size-, time-, and concentration-dependent manner. This interaction induced significant morphological changes and increased hydrophilicity on the polymer surface. Furthermore, a positive correlation was observed between the activities of laccase and manganese peroxidase and a measurable weight loss in LDPE films, suggesting direct enzymatic involvement in polymer degradation. Crucially, the DCP04 strain also met key safety and functional criteria for use as a probiotic. These findings highlight the potential of DCP04 strain as a functional probiotic agent for mitigating the accumulation of MPs and NPs within the human body.