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Re-degradation of residual plastic in frass of Zophobas morio larvae after plastic ingestion and degradation

Journal of Hazardous Materials 2026
Bin Ding, Yun Jia, Ren-tao He, Cong Liang

Summary

Superworms (Zophobas morio larvae) can eat and break down foam plastic, but scientists worried the leftover plastic bits in their waste might still pollute the environment. This study found that when the larvae eat their own plastic-containing waste a second time, they break it down even further—and surprisingly, this second round causes less gut damage than eating fresh plastic did, thanks to helpful gut bacteria and protective molecules. This suggests a cheap, natural way to help tackle plastic waste, though more research is needed before this translates into real-world solutions for reducing microplastic pollution that ends up in our food and water.

Polymers
Body Systems

Zophobas morio larvae can feed on and digest polyolefin plastic foams, but undegraded plastic residues in their frass pose a risk of secondary pollution. This study demonstrates that these larvae can further process such residual plastics. Z. morio larvae re-degradation of plastic residues in frass, reducing the number-average molecular weight (Mn) by 94.63% and the weight-average molecular weight (Mw) by 54.47%. These reductions are greater than those achieved when the larvae degrade the original polystyrene plastic (73.10% for Mn and 9.36% for Mw). Analysis of the intestinal microbiota indicated that, the abundance of Lactococcus, a microorganism with PS-degrading capabilities, is higher in larvae degrading fecal plastics than in those degrading original plastics. Moreover, larvae degrading fecal plastics (F Group) experience less intestinal damage than those degrading original plastics (PS Group). This is associated with the significant increase of metabolites with antioxidant or antibacterial properties such as 3-Hydroxymelatonin, 2-O-Caffeoylhydroxycitric acid, and D-sphingosine in the intestines of the F Group. Moreover, the F Group shows up-regulated expression of genes and proteins related to intestinal barrier function and digestive metabolism, along with reduced nicotinamide adenine dinucleotide phosphate (NADP⁺) abundance compared with the PS Group. Overall, this study offers a low-cost, straightforward approach to mitigating secondary pollution caused by residual fecal plastics after larval plastic degradation.

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