Sustainable Bioremediation of Plastic Waste: How the Flame Retardant TCPP Affects Polyurethane Foam Biodegradation by Galleria mellonella Larvae

As a common substitute for brominated flame retardants (BFRs), organophosphate flame retardants (OPFRs) have been insufficiently studied in terms of their ecotoxicological impacts on plastic biodegradation processes in invertebrate systems. This study investigated the impact of an OPFR, tris (1-chloro-2-propyl) phosphate (TCPP), on the dietary behavior and gut microbiota of Galleria mellonella (Linnaeus, 1758) (Lepidoptera: Pyralidae) larvae during the biodegradation of rigid polyurethane (RPU), as well as the fate of TCPP. The results show that TCPP interfered with larval feeding activity, hindered the nutritional conversion of food, and triggered metabolic compensation through lipid reserve catabolism. Notably, mass balance analysis revealed that bioaccumulation of TCPP was negligible, with most of it excreted through frass, indicating limited biodegradation of this organophosphate ester. 16S rRNA sequencing indicated that TCPP drove the reconstruction of gut microbiota in larvae and identified three dominant bacteria of Morganellaceae, Enterobacteriaccae, and Staphylococcaceae families, as well as non-dominant bacteria of Klebsiella and Vagococcaceae families, as characteristic microbiota contributing to RPU and TCPP biotransformation. This study serves as a reminder to pay attention to the toxicity, migration, and transformation of OPFRs in biodegradable plastics. Notably, TCPP, a dominant chlorinated OPFR, exhibits environmental persistence with limited biodegradability and low bioaccumulation, traits which hinder the spontaneous attenuation of plastic waste in ecosystems and undermine the sustainability of the plastic lifecycle. This work emphasizes the need to integrate risk assessments of specific additives into the plastic waste management framework and to develop targeted detoxification strategies for promoting a sustainable material lifecycle.