(663d) Thermoplastic Degradation By Yellow Mealworm Gut Microbial Communities and Isolates

To address the significant thermoplastic waste problem, we sought a biological strategy for plastics depolymerization from the gut microbiomes of the yellow mealworm. While bacterial community members have been identified, the specific pathways responsible for biodegradation remain to be elucidated and the potential contributions of fungal members are unexamined. Additionally, emerging evidence suggests that nutrient supplementation enhances plastic metabolism up to 70% and gives rise to a gut community structure distinct from that without additional nutrients. However, it is unclear if nutrient supplementation induces microbes to participate in the plastic degradation or if it supports a more optimal community composition.

In our study, we measured consumption rates of PS, LDPE, and HDPE of 20.4, 12, and 1.1, mg per (100 larvae) per day, respectively. However, nutrient supplementation enhanced plastics consumption by 158.8, 60, and 232.1 %, respectively. Antibiotic and antifungal selection studies suggest that fungal communities in the mealworm gut microbiome are likely to play an important role in the plastic consumption and that the inter-kingdom relationship between bacteria and fungi may be antagonistic. Fourier transform infrared spectroscopy (FTIR) analysis of frass (excrement) from mealworms fed PS and LDPE revealed incorporation of oxygen not found in untreated controls. Thermogravimetric analyses (TGA) of frass also confirmed the changes in physical properties. Finally, gel permeation chromatography (GPC) of the frass confirmed decreased apparent polymer molecular weight. Taken together, these results demonstrate that the plastics being ingested by the larvae are being oxidized and depolymerized. Microbiome community analysis via 16s and ITS sequencing revealed a rich consortium of bacteria and fungi. Mealworm diet led to unique community structures adapted to degradation of the fed plastic substrate, where nutrient supplementation frequently selected for taxa that were not observed in plastics only or nutrient only controls, suggesting currently unrecognized interactions.

Finally, characterization of the cultivable microbial community and isolates revealed a rich landscape of plastic depolymerization activities from microbes known to degrade plastics as well as several new genera that have never before been reported for their plastic degrading capabilities. We will present evidence strongly supporting the depolymerization of PS and LDPE, and synergistic activities of combinations of isolates for enhanced degradation.