Biodegradation
and Mineralization of Polystyrene by
Plastic-Eating Mealworms: Part 2. Role of Gut Microorganisms
- Publication date
- Publisher
Abstract
The
role of gut bacteria of mealworms (the larvae of Tenebrio
molitor Linnaeus) in polystyrene (PS) degradation
was investigated. Gentamicin was the most effective inhibitor of gut
bacteria among six antibiotics tested. Gut bacterial activities were
essentially suppressed by feeding gentamicin food (30 mg/g) for 10
days. Gentamicin-feeding mealworms lost the ability to depolymerize
PS and mineralize PS into CO<sub>2</sub>, as determined by characterizing
worm fecula and feeding with <sup>13</sup>C-labeled PS. A PS-degrading
bacterial strain was isolated from the guts of the mealworms, Exiguobacterium sp. strain YT2, which could form
biofilm on PS film over a 28 day incubation period and made obvious
pits and cavities (0.2–0.3 mm in width) on PS film surfaces
associated with decreases in hydrophobicity and the formation of C–O
polar groups. A suspension culture of strain YT2 (10<sup>8</sup> cells/mL)
was able to degrade 7.4 ± 0.4% of the PS pieces (2500 mg/L) over
a 60 day incubation period. The molecular weight of the residual PS
pieces was lower, and the release of water-soluble daughter products
was detected. The results indicated the essential role of gut bacteria
in PS biodegradation and mineralization, confirmed the presence of
PS-degrading gut bacteria, and demonstrated the biodegradation of
PS by mealworms