Harnessing microbial consortia for microplastic degradation in soil–plant systems

Microplastics are persistent pollutants in aquatic and terrestrial environments, impacting habitats, transporting co-contaminants, and influencing microbial, animal, and plant functions. This review critically examines the microbial degradation of six key polymer groups—polyethylene terephthalate, polyurethane, polyethylene, polypropylene, polystyrene, and poly(vinyl chloride), with a focus on microbial communities and their roles in soil–plant systems. Of 18 microbial systems assessed, only 4 showed direct evidence of polymer-derived carbon uptake or mineralization via stable-isotope tracing or utilization of polymer monomers. Most research relied on mass loss, microscopy, or spectroscopy, which suggest polymer alteration but does not definitively confirm biodegradation. Studies reported up to 21.81% mass loss for high-density polyethylene and 26.3% for low-density polyethylene, but these are not directly comparable due to variations in polymer properties, pretreatment, and experimental setups. Five functional consortium types were identified: initiator–processor, cross-kingdom, sequential degradation–detoxification, habitat-adapted, and process-coupled or rhizosphere-integrated systems. Rhizosphere-associated consortia show promise for soil remediation in agriculture, but field application requires precise carbon measurements, thorough characterization and toxicity assessment of degradation products, and long-term monitoring of consortium stability and ecological effects. Future research should combine soil and rhizosphere metagenomics, metatranscriptomics, and metabolomics with whole-genome sequencing of consortium members. When paired with stable-isotope probing, these methods can identify active microbes and pathways involved in polymer-carbon assimilation in soil-plant systems.