A polystyrene-degrading Acinetobacter bacterium isolated from the larvae of Tribolium castaneum

Polystyrene (PS) has been widely used in various fields, whereas this thermoplastic material is generally considered to be resistant to biodegradation. Tribolium castaneum (Coleoptera: Tenebrionidae), a common pest of stored agricultural products, is a powerful model organism for general insect research. In this study, the larvae of T. castaneum were observed chewing and eating extruded polystyrene foam (XPS). Investigation of the gut microbiome of plastic- and bran-fed T. castaneum larvae showed that Acinetobacter sp. was strongly associated with PS ingestion. Additionally, one bacterial strain capable of PS degradation, was successfully isolated from the gut of these larvae and identified as Acinetobacter sp. AnTc-1 by its 16S rDNA sequence. Gel penetration chromatography (GPC), ¹H nuclear magnetic resonance (¹H NMR) spectroscopy, thermo gravimetric analysis (TGA) and scanning electron microscope (SEM) were employed to characterize the PS degradation. After incubation with AnTc-1 for 60 days, the mass weight (12.14%) and molecular weight (13%/25%, weight-average molecular weight (Mw)/number-average molecular weight (Mn)) of PS powder were significantly reduced. The results indicated that the isolated strain of Acinetobacter sp. AnTc-1 has PS-degrading capacity. The isolated strain may play a role in the larval gut for biodegradation of PS and has potential to be applied for petroleum-based plastic degradation study and development of remediation approaches.