Biodegradation of Pristine and Post-Consumer Extruded Expanded Polystyrene Packaging by Zophobas atratus Larvae: Influence of the Larval Stage and Physiological Response

TL;DR

Zophobas atratus larvae can biodegrade polystyrene, with different stages and types of plastic affecting the process and larval health.

Contribution

This study is the first to evaluate Zophobas atratus larvae's biodegradation of polystyrene and its physiological effects across larval stages.

Findings

Larger larvae (L2) consumed more polystyrene and had higher survival and weight gain compared to smaller larvae (L1).

XPS-fed larvae showed reduced lipid content and increased moisture, flavonoids, and phenolics compared to controls.

L1 larvae were more effective in degrading pristine XPS, while L2 larvae were more effective on post-consumer XPS.

Abstract

Plastics are inexpensive and widely used but persist in the environment due to improper disposal. Insect-mediated biodegradation has gained attention, notably involving Tenebrio molitor larvae. Despite morphological similarities and larger size, Zophobas atratus larvae remain less studied. This work evaluated the impact of larval stage on the biodegradation of pristine and post-consumer extruded polystyrene (XPS) and the physiological effects of an XPS-based diet. Smaller (L1) and larger (L2) larvae were tested. L2 showed higher XPS consumption, weight gain, and survival, while XPS-fed larvae overall exhibited reduced lipid content and increased moisture, flavonoids, and phenolics compared to wheat bran-fed controls. Scanning electron microscopy revealed surface fragmentation in frass, more pronounced in L1, suggesting greater mechanical or enzymatic action. High-performance size exclusion chromatography indicated molecular weight reduction, with L1 more effective on pristine XPS and L2 on post-consumer XPS, likely due to nutritional residues. FTIR analysis showed oxidative changes in both groups, more prominent in L1. Thermogravimetric analysis revealed earlier degradation onset in L1 frass, supporting the presence of oxidized oligomers. Overall, Z. atratus larvae can biodegrade XPS, with degradation influenced by developmental stage and substrate type. These findings inform biotechnological strategies for sustainable plastic waste management.

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