Responses of gut microbiomes to commercial polyester polymer biodegradation in Tenebrio molitor Larvae

Polyethylene terephthalate (PET) is a mass-produced fossil-based plastic polymer that contributes to catastrophic levels of plastic pollution. Here we demonstrated that Tenebrio molitor (mealworms) was capable of rapidly biodegrading two commercial PET resins (microplastics) with respective weight-average molecular weight (M_w) of 39.33 and 29.43 kDa and crystallinity of 22.8 ± 3.06% and 18 ± 2.25%, resulting in an average mass reduction of 71.03% and 73.28% after passage of their digestive tract, and respective decrease by 9.22% and 11.36% in M_w of residual PET polymer in egested frass. Sequencing of 16 S rRNA gene amplicons of gut microbial communities showed that dominant bacterial genera were enriched and associated with PET degradation. Also, PICRUSt prediction exhibited that oxidases (monooxygenases and dioxygenases), hydrolases (cutinase, carboxylesterase and chitinase), and PET metabolic enzymes, and chemotaxis related functions were up-regulated in the PET-fed larvae. Additionally, metabolite analyses revealed that PET uptake caused alterations of stress response and plastic degradation related pathways, and lipid metabolism pathways in the T. molitor larvae could be reprogrammed when the larvae fed on PET. This study provides new insights into gut microbial community adaptation to PET diet under nutritional stress (especially nitrogen deficiency) and its contribution to PET degradation.