Abstract
Plastic waste management has become a global issue. Polyethylene (PE) is the most abundant synthetic plastic worldwide, and one of the most resistant to biodegradation. Indeed, few bacteria can degrade polyethylene. In this paper, the transcriptomic analysis unveiled for the first time Rhodococcus opacus R7 complex genetic system based on diverse oxidoreductases for polyethylene biodegradation. The RNA-seq allowed uncovering genes putatively involved in the first step of oxidation. In-depth investigations through preliminary bioinformatic analyses and enzymatic assays on the supernatant of R7 grown in the presence of PE confirmed the activation of genes encoding laccase-like enzymes. Moreover, the transcriptomic data allowed identifying candidate genes for the further steps of short aliphatic chain oxidation including alkB gene encoding an alkane monooxygenase, cyp450 gene encoding cytochrome P450 hydroxylase, and genes encoding membrane transporters. The PE biodegradative system was also validated by FTIR analysis on R7 cells grown on polyethylene.
Highlights
IntroductionPolyethylene (PE) is the most abundant synthetic plastic worldwide, and one of the most resistant to biodegradation
Plastic waste management has become a global issue
R. opacus strain R7, which was selected for its ability to degrade numerous aliphatic, mono- and polycyclic aromatic hydrocarbons, and cyclo-carboxylic acids[24], was preliminarily tested for the ability to grow on PE by a plate agar assay dissolving the PE powder in 1% Tween[80]
Summary
Polyethylene (PE) is the most abundant synthetic plastic worldwide, and one of the most resistant to biodegradation. In the last two centuries, plastic played a revolutionary role for its versatile properties, including convenience, non-degradability, durability, and low cost replacing other natural materials for packaging, transportation, storage, and garbage[1]. The most used synthetic polymer is polyethylene (PE) for its chemical–physical and mechanical properties such as high hydrophobicity, chemical resistance, electrical isolation, high breaking strength, high stability against deterioration, and low production c osts[3]. Albertsson and coworkers[10] suggested that a synergistic effect between photooxidative degradation and biodegradation can facilitate the PE degradation: UV light and/or oxidizing agents begin the degradation, and after carbonyl group formation, microorganisms degrade the shorter segments starting from the oxidized PE chains forming carbon dioxide and water as end products.
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