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

Yu Yang†, Jun Yang*†, Wei-Min Wu‡, Jiao Zhao§, Yiling Song∥, Longcheng Gao†, Ruifu Yang§, and Lei Jiang*†

†Key Laboratory of Bio-Inspired Smart Interfacial Science and Technology of Ministry of Education, School of Chemistry and Environment, and ∥School of Biological Science and Medical Engineering, Beihang University, Beijing 100191, People’s Republic of China

‡ Department of Civil and Environmental Engineering, William & Cloy Codiga Resource Recovery Research Center, Center for Sustainable Development & Global Competitiveness, Stanford University, Stanford, California 94305-4020, United States

§ Shenzhen Key Laboratory of Bioenergy, BGI-Shenzhen, Shenzhen, Guangdong 518083, People’s Republic of China

Environ. Sci. Technol., 2015, 49 (20), pp 12080–12086
DOI: 10.1021/acs.est.5b02661
Publication Date (Web): September 21, 2015

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.