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Biodegradation Mechanism of Polystyrene by Mealworms (Tenebrio molitor) and Nutrients Influencing Their Growth

Journal of Materials Science 2024 8 citations ? Citation count from OpenAlex, updated daily. May differ slightly from the publisher's own count.
Hisayuki Nakatani, Yuto Yamaura, Yuma Mizuno, Suguru Motokucho, Anh Dao, Hiroyuki Nakahara

Summary

This study investigated how mealworms (Tenebrio molitor) break down polystyrene, finding that gut microbes drive radical oxidative reactions — including autoxidation and quinonization — that reduce molecular weight by 33% within a week, though mealworms require additional nutrients like protein, phosphorus, and magnesium to actually grow on plastic-only diets.

Polymers

A degradation mechanism of polystyrene (PS) in mealworms reared on expanded PS (EPS) was investigated by its decrease in molecular weight and change in chemical structure. A 33% decrease in molecular weight was observed for the digested PS in the frass after 1 week of feeding to mealworms. The FT-IR and py-GC/MS spectra of the digested PS showed radical oxidative reactions taking place in the mealworm body. The presence of hydroperoxide, alcohol and phenol groups was confirmed, and dimer fragments of styrene with quinone and phenol groups were obtained. The decrease in molecular weight and the alternation of benzene rings indicated that autoxidation and quinonization via phenolic intermediates occurred simultaneously in the mealworm body. The survival rate of mealworms reared on EPS was higher than that of starved worms, indicating that EPS was a nutrient source. However, no weight gain was observed in mealworms fed EPS alone. Comparison with the mixed diets with bran or urethane foams (PU) indicated that protein, phosphorus and magnesium components absent from EPS were required for mealworm growth.

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