Biodegradation and Mineralization of Polystyrene by Plastic-Eating Mealworms: Part 1. Chemical and Physical Characterization and Isotopic Tests

TLDR

Polystyrene is widely regarded as durable and resistant to biodegradation. The study investigates whether mealworms can consume and degrade Styrofoam, a common polystyrene product. Analyses of larval fecula by GPC, CP/MAS NMR, and TG–FTIR confirmed that gut enzymes cleave long‑chain PS into depolymerized metabolites. Styrofoam was rapidly degraded within 24 h, with 47.7 % of ingested carbon released as CO₂, 49.2 % excreted as fecula, 0.5 % incorporated into biomass, and labeled PS mineralized to CO₂ and lipids, demonstrating that mealworms offer a viable route for polystyrene waste disposal.

Abstract

Polystyrene (PS) is generally considered to be durable and resistant to biodegradation. Mealworms (the larvae of Tenebrio molitor Linnaeus) from different sources chew and eat Styrofoam, a common PS product. The Styrofoam was efficiently degraded in the larval gut within a retention time of less than 24 h. Fed with Styrofoam as the sole diet, the larvae lived as well as those fed with a normal diet (bran) over a period of 1 month. The analysis of fecula egested from Styrofoam-feeding larvae, using gel permeation chromatography (GPC), solid-state 13C cross-polarization/magic angle spinning nuclear magnetic resonance (CP/MAS NMR) spectroscopy, and thermogravimetric Fourier transform infrared (TG–FTIR) spectroscopy, substantiated that cleavage/depolymerization of long-chain PS molecules and the formation of depolymerized metabolites occurred in the larval gut. Within a 16 day test period, 47.7% of the ingested Styrofoam carbon was converted into CO2 and the residue (ca. 49.2%) was egested as fecula with a limited fraction incorporated into biomass (ca. 0.5%). Tests with α 13C- or β 13C-labeled PS confirmed that the 13C-labeled PS was mineralized to 13CO2 and incorporated into lipids. The discovery of the rapid biodegradation of PS in the larval gut reveals a new fate for plastic waste in the environment.