Biodegradation of Polystyrene by Dark (Tenebrio obscurus) and Yellow (Tenebrio molitor) Mealworms (Coleoptera: Tenebrionidae)

Abstract

Yellow mealworms (larvae of Tenebrio molitor, Coleoptera: Tenebrionidae) have been proven to be capable of biodegrading polystyrene (PS) products. Using four geographic sources, we found that dark mealworms (larvae of Tenebrio obscurus) ate PS as well. We subsequently tested T. obscurus from Shandong, China for PS degradation capability. Our results demonstrated the ability for PS degradation within the gut of T. obscurus at greater rates than T. molitor. With expanded PS foam as the sole diet, the specific PS consumption rates for T. obscurus and T. molitor at similar sizes (2.0 cm, 62–64 mg per larva) were 32.44 ± 0.51 and 24.30 ± 1.34 mg 100 larvae–1 d–1, respectively. After 31 days, the molecular weight (M n) of residual PS in frass (excrement) of T. obscurus decreased by 26.03%, remarkably higher than that of T. molitor (11.67%). Fourier transform infrared spectroscopy (FTIR) indicated formation of functional groups of intermediates and chemical modification. Thermo gravimetric analysis (TGA) suggested that T. obscurus larvae degraded PS effectively based on the proportion of PS residue. Co-fed corn flour to T. obscurus and wheat bran to T. molitor increased total PS consumption by 11.6% and 15.2%, respectively. Antibiotic gentamicin almost completely inhibited PS depolymerization. High-throughput sequencing revealed significant shifts in the gut microbial community in both Tenebrio species that were associated with the PS diet and PS biodegradation, with changes in three predominant families (Enterobacteriaceae, Spiroplasmataceae, and Enterococcaceae). The results indicate that PS biodegradability may be ubiquitous within the Tenebrio genus which could provide a bioresource for plastic waste biodegradation.

Microbial Degradation and Valorization of Plastic Wastes

“…With the same protocols, the PS-degrading capability was also documented in a broader range of mealworms from 12 different locations worldwide, indicating that PS degradation in mealworms is ubiquitous . This discovery also inspired researchers to explore more insect species, such as dark mealworms (Tenebrio obscurus) (Peng et al, 2019) and superworms (Zophobas atratus) (Yang et al, 2020), that also could eat and degrade PS.…”

Insects as food and feed, a new emerging agricultural sector: a review

“…However, although the foam feeds can maintain the insect's life and produce eggs, it was not economically feasible (Nukmal et al, 2018). Tenebrio obscurus has also been proposed as a likely candidate to be able to degrade plastics (Peng et al, 2019).…”

Evaluation of the Biodegradation Efficiency of Four Various Types of Plastics by Pseudomonas aeruginosa Isolated from the Gut Extract of Superworms

“…Recently, several plastic-ingesting worms capable of removing plastic wastes have been reported, including waxworms ( Galleria mellonella L.), mealworms ( Tenebrio molitor L.) and superworms ( Zophobas atratus L.), which can depolymerize polyethylene (PE) and polystyrene (PS) upon ingestion [ 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 ]. Further studies have shown that treatment with antibiotic compounds to remove gut bacteria within the worms significantly reduces the biodegradation efficiency with respect to ingested PE and PS, suggesting that gut bacteria participate in plastic biodegradation in these worms [ 9 , 10 , 15 ]. Several gut bacterial species isolated from worms have been verified to be able to mediate plastic biodegradation directly.…”