Plastic pollution remains one of the most persistent environmental crises, with polystyrene (PS) among the hardest polymers to break down due to its stable aromatic backbone. A new study demonstrates that the cockroach Blaptica dubia can efficiently biodegrade polystyrene through a tightly integrated gut microbe–host metabolic system. The insects removed nearly 55% of ingested polystyrene within 42 days, achieving a degradation rate far exceeding those reported for other plastic-feeding insects. Analyses of residual polymer in frass versus original PS confirmed depolymerization, oxidation, enrichment of stable isotope 13C and partial mineralization. By coupling microbial enzymatic cleavage with host β-oxidation and tricarboxylic acid cycle pathways, the cockroach transforms plastic-derived carbon into metabolic energy, revealing a powerful biological strategy for tackling recalcitrant synthetic polymers.
Global plastic production now exceeds 400 million tons annually, and PS remains one of the most widely used yet environmentally persistent polymers because of its aromatic backbone and chemically stable carbon–carbon bonds. Once fragmented into microplastics, PS can accumulate in soils and aquatic systems as well atmosphere, adsorb pollutants, and enter food webs. Although several insect species, such as mealworms and greater wax moth larvae, have shown partial biodegradation capacity, their degradation rates remain modest, and the metabolic fate of breakdown intermediates is poorly resolved. Most previous studies focused primarily on gut microbes or depolymerization alone. In light of these challenges, a deeper investigation into coordinated host–microbiome metabolic mechanisms is urgently needed.
Researchers from Harbin Institute of Technology with collaborators at Stanford University reported the findings (DOI: 10.1016/j.ese.2026.100679) on February 25, 2026, in Environmental Science and Ecotechnology . The team investigated the biodegradation capacity of the cockroach Blaptica dubia, integrating metagenomics, transcriptomics, 13C isotope signature, and polymer chemistry analyses. Their results reveal a coordinated microbe–enzyme–host metabolic network that enables rapid depolymerization, biodegradation of daughter intermediates, and metabolic assimilation of polystyrene microplastics, offering new insight into how insects may adapt to synthetic carbon sources in the Anthropocene.
In controlled feeding experiments, cockroaches consumed an average of 6.0 mg of polystyrene per individual per day. Over 42 days, they removed 54.9% of ingested plastic, corresponding to a specific degradation rate of 3.3 mg per cockroach per day—an order of magnitude higher than rates reported in mealworms, superworms and other plastic-degrading insects. Gel permeation chromatography revealed significant polymer breakdown, with number-average molecular weight decreasing by 46.4%. Stable carbon isotope analysis showed enrichment of δ¹³C in residual plastic, confirming preferential metabolic utilization of lighter carbon isotopes which is strong indication of biological reactions. FTIR, NMR, thermogravimetric, and Py-GC/MS analyses detected newly formed oxygen-containing functional groups, demonstrating oxidative chain scission and aromatic ring modification.
Metagenomic sequencing revealed that polystyrene feeding reshaped the gut microbiome toward plastic-degrading taxa such as Pseudomonas, Citrobacter, Klebsiella, and Stenotrophomonas, accompanied by enrichment of oxidoreductases and transferases. Network analysis showed tightly connected microbe–enzyme modules driving aromatic oxidation. Meanwhile, host transcriptomics revealed strong upregulation of β-oxidation, NADH dehydrogenase, oxidative phosphorylation, and TCA cycle pathways, indicating that microbial degradation intermediates were absorbed and metabolically integrated. Together, these findings outline a synergistic cascade: microbial oxidative depolymerization followed by host energy assimilation.
"This work demonstrates that plastic degradation in insects is not merely a microbial phenomenon, but a fully integrated metabolic collaboration," said the study's corresponding author. "The cockroach does not simply fragment polystyrene—it metabolically processes the breakdown products through its own energy pathways. The coupling of microbial oxidation with host β-oxidation and the TCA cycle represents a systemic adaptation to synthetic carbon sources." The researchers emphasize that this tripartite host–microbe–enzyme cooperation explains the unusually high degradation efficiency observed.
The discovery expands the biological toolkit available for addressing plastic pollution. Rather than relying solely on isolated enzymes or engineered microbes, future strategies may draw inspiration from integrated host–microbiome systems capable of both depolymerization and carbon reutilization. Although direct environmental release of cockroaches that includes more than 4,400 species around the world is not currently practical or advisable, decoding their metabolic networks could inform synthetic biology approaches, microbial consortia design, or enzyme engineering platforms for plastic waste valorization. More broadly, the findings suggest that insects may possess unexpected evolutionary flexibility to adapt to anthropogenic polymers, offering a new paradigm for sustainable bioremediation in a plastic-dominated world.
