Ingestion preference and efficiencies of different polymerization types foam plastics by Tenebrio molitor larvae, associated with changes of both core gut bacterial and fungal microbiomes

The discovery that insect larvae can feed on kinds of foam plastics opened new avenues and provided a potential solution for plastic wastes biodegradation. This study aimed to investigate whether plastic polymerization types had regular impacts on larvae growth, gut microbial communities and functional microbes, foam plastics of polypropylene (PP), polyurethane (PU) and ethylene vinyl acetate (EVA) were selected as the representatives of different polymerized plastic and sole diets for yellow mealworms of Tenebrio molitor larvae for 45 days, with sole bran diet as control. Our findings showed that although slightly weight gains were obtained in plastic-fed groups, the larval survival rates decreased to 61.33 %, 59.67 % and 24.00 % in PP-, PU- and EVA-fed groups, respectively. The EVA-fed group was even lower than the starvation group, indicating that the more complex polymers diet had worse adverse effects on larval survival. The gut bacterial- and fungal-microbiomes assessed by Illumina MiSeq indicated that both gut bacterial and fungal communities shifted upon diets of different polymerization types compared to the control. The gut dominant abundances of Spiroplasma, Acinetobacter and Pseudomonas in PP-fed group were significantly different from that of unclassified Enterobacteriaceae in both PU- and EVA-fed groups. In contrast, all gut fungal communities in plastics-fed groups were similar with the dominants of Rhodotorula and Cryptococcus, but more abundances that had been reported with plastics degradation ability were obtained, such as Aspergillus and Cladosporium. In summary, T. molitor could efficiently degrade complex polymers, albeit with adverse effects. Core gut microbiomes were strongly associated with polymerization types of plastic diet, especially gut fungi.