A Preliminary Study on Polyurethane Foam Ingestion by Tenebrio molitor Larvae and Potential Effects of Depolymerising Bacterial Supplementation

Intake and utilisation of polyurethane foam by Tenebrio molitor larvae, and the potential contribution of depolymerising bacteria (Kocuria rhizophila, Priestia megaterium and Cupriavidus respiraculi) used as probiotics, were evaluated. In Experiment 1, larvae were raised without substrate or with polyurethane foam, with fresh carrot provided as a water source. Mortality (23.8%) was unaffected by treatment (p > 0.10), and polyurethane disappearance averaged 22.1 mg/larva. Larval growth (p = 0.042) and frass output (p < 0.001) were higher in polyurethane-fed larvae. In Experiment 2, treatments consisted of polyurethane alone (PU), with wheat bran (PUB), or wheat bran and a mixed bacterial culture (PUBP). Larval growth and total mass production were higher in PUB and PUBP than in PU (p < 0.001), although numerical improvements in PUBP compared to PUB were not significant. Polyurethane disappearance did not differ (9.85 mg/larva, as an average), whereas frass production was higher in PUBP than in PU, with intermediate values for PUB (p < 0.001). Microscopic examination revealed numerous polyurethane particles in frass, indicating ingestion and fragmentation. However, no direct evidence of polymer biodegradation or microbial activity within the larval gut was obtained. In conclusion, T. molitor larvae ingested polyurethane foam independently of the additional substrate supply, although these findings should be interpreted with caution and degradation mechanisms need to be contrasted in further studies.