Innovative soil seeding with waste-derived microbial inoculums: Enhancing plastic biodegradation and revealing...

Plastic waste accumulation in terrestrial ecosystems poses a global environmental challenge, demanding sustainable alternatives to conventional disposal. Aerobic biodegradation is promising, yet most studies rely on composting systems, often overlooking different polymer types and how seeding soil with waste-derived inoculums affects polymer breakdown. This study developed an innovative soil-seeding approach using microbe-rich inoculums derived from real waste streams: compost (Comp.), activated sludge (AS), plastic-contaminated soil (PCS), and oil-contaminated soil (OCS) to enhance biodegradation of starch, compostable bioplastic (CBP), and the mineralization of linear low-density polyethylene (LLDPE). Biodegradation was evaluated under controlled soil conditions, and microbial community responses were characterized through metataxonomic profiling. Starch exhibited the highest biodegradation (71-100%), followed by CBP (31-56%) and LLDPE mineralization (12-22%). OCS and PCS significantly enhanced CBP and LLDPE degradation, respectively, corresponding to differences in organic content and carbon-to-nitrogen ratios. Shifts in microbial composition revealed polymer-specific microbial drivers, including Bacilli (Bacillaceae, Paenibacillus) and Chaetomium for starch, and Actinobacteriota, Acidimicrobiia, Mycobacterium, and Nocardioides for CBP, particularly in OCS. LLDPE degradation remained low but was modestly improved in Comp.- and PCS-amended soils. Overall, this study demonstrates that targeted soil-seeding with waste-derived inoculums can substantially influence polymer degradation and microbial succession, providing a practical strategy to accelerate biodegradation in natural soils and informing future sustainable plastic-management approaches.