Sustainable approach to polystyrene management and bioinsecticide production: Biodegradation by Tenebrio molitor larvae co-fed with residual biomass and bioactivity of frass pyrolysis bio-oil against insect pests

Tenebrio molitor has gained attention as a potential solution for plastic pollution. This study explored the biodegradation of polystyrene (PS) by mealworms co-fed with rice bran (RB) under an optimized rearing scheme. The RB co-diet significantly increased PS consumption by two-fold compared to wheat bran (WB). Additionally, RB supported mealworm growth with favorable survival and feed conversion rates. Protein content of mealworms remained unchanged with PS plus RB, while significantly increased lipid stores and improved the fatty acid profile. Frass from PS (1) and biomass (2) intake was subjected to pyrolysis. Bio-oils from frass 2 exhibited insecticidal activity against Plodia interpunctella adults and Culex pipiens pipiens larvae. Finally, bio-oils demonstrated low toxicity to the aquatic non-target species Artemia salina, with up to three-fold selectivity towards Cx. p. pipiens. These findings highlight RB's role in PS management and the potential application of bio-oil as bioinsecticide.