Microbial and Insect Gut-Mediated Polystyrene Microplastic Degradation for Environmental Remediation Applications

Polystyrene (PS), particularly expanded polystyrene (EPS), is an environmentally significant commodity polymer that contributes substantially to secondary microplastic and nanoplastic pollution through environmental weathering and fragmentation. During aging, PS undergoes nano-scale physicochemical transformations, including chain scission, surface oxidation, and the formation of oxygen-containing functional groups, which profoundly influence its environmental fate, microbial colonization, and biodegradation behavior. Conventional remediation technologies remain energy-intensive and often fail to achieve complete mineralization, highlighting the need for sustainable and integrated remediation strategies. Recent studies have demonstrated that diverse microorganisms, including Pseudomonas, Rhodococcus, Bacillus, and Exiguobacterium, can colonize PS surfaces and initiate oxidative depolymerization through extracellular biofilm formation and oxidative enzymes such as styrene monooxygenase, laccases, and peroxidases. In parallel, insect-based systems, particularly Tenebrio molitor and Zophobas morio, provide unique biological platforms in which gut microbiota facilitate partial PS degradation and mineralization through synergistic host–microbe interactions. This review critically integrates recent advances in nano-scale PS transformation, microbial colonization, oxidative enzymatic pathways, insect gut-mediated biodegradation, and advanced analytical techniques used to characterize degradation processes. Emphasis is placed on nano–bio interactions and emerging nanotechnology-enabled remediation strategies, including engineered microbial consortia, biofilm-based bioreactors, and nanomaterial-assisted treatment systems. Finally, current limitations and future research priorities are discussed, including degradation kinetics, byproduct toxicity, standardized evaluation methods, and the integration of biological and nanomaterial-based approaches for scalable PS microplastic remediation.