Biodegradation of polylactic acid by yellow mealworms (larvae of Tenebrio molitor) via resource recovery: A sustainable approach for waste management

Polylactic acid (PLA) is biodegraded rapidly under composting or thermophilic temperature but slowly under natural conditions with substantial microplastics generated. In this study, we examined the feasibility of PLA biodegradation and developed a novel approach for PLA waste management using yellow mealworms (Tenebrio molitor larvae) to achieve biodegradation and resource recovery simultaneously. Results confirmed PLA biodegradation in mealworms as sole PLA and PLA-bran mixtures (10%, 20%, 30% and 50% PLA, wt/wt). Feeding PLA-bran mixtures supported the larval development with higher survival rates and lower cannibal rates than feeding PLA only at ambient temperature. The PLA conversion efficiency was 90.9% with 100% PLA diet and was around 81.5–86.9% with PLA-bran mixtures. A peak insect biomass yield was achieved at a PLA ratio of 20%. PLA biodegradation was verified via detection of chemical and thermal modifications. Gut microbial community analysis indicated that intestinal communities shifted with PLA biodegradation, resulting in clusters with OTUs unique to the PLA diet. Based on these findings, we propose a circular approach for PLA waste management via resource recovery of used PLA as the feedstock for insect biomass production, management of mealworm excrement waste as fertilizer, and utilization of agricultural products for PLA production.