Exploring a New Biocatalyst from Bacillus thuringiensis JNU01 for Polyethylene Biodegradation

Abstract

The decomposition of polyethylene (PE), an extremely recalcitrant synthetic polymer, using microorganisms is an ideal and sustainable method for future PE biotreatment. We isolated a set of PE-biodegrading Bacillus species from a landfill site. Among them, Bacillus thuringiensis JNU01 exhibited the highest cell growth rate in PE media, which means it effectively decomposed PE to use in the metabolic pathway as a sole carbon source. B. thuringiensis JNU01-treated PE showed new chemical functional groups such as hydroxyl, carboxyl, and amide groups in the inert hydrocarbon. Scanning electron microscopy revealed considerable physical damage on the surface of the PE film after treatment with B. thuringiensis JNU01. Furthermore, various alkane derivatives obtained from PE were characterized using gas chromatography–mass spectrometry. On the contrary, an increase in the mRNA transcriptional levels of B. thuringiensis JNU01 in the presence of PE suggests that a CYP102A5 variant (CYP102A5.v1) is involved in PE biodegradation. Finally, we confirmed that purified CYP102A5.v1 catalyzes the hydroxylation of PE by a NADPH oxidation assay and Fourier transform infrared analysis. These results show that B. thuringiensis JNU01 is a potential PE decomposer and suggest that CYP102A5.v1 can be a trigger biocatalyst for hydroxylation of PE.

Biotechnological Plastic Degradation and Valorization Using Systems Metabolic Engineering

“…Numerous microorganisms exhibiting plastic degradation capabilities have been identified in diverse environments [8]. Moreover, the degradation ability of these microorganisms/enzymes is evaluated using various methods such as the following: (1) using scanning electron microscopy (SEM), atomic force microscopy (AFM), and water contact angle (WCA) analysis to monitor the change in surface structure and hydrophobicity [9,10]; (2) using a universal mechanical testing system to assess changes in mechanical properties [11]; (3) simple weighing to investigate weight loss [12]; (4) Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and nuclear magnetic resonance (NMR) to identify the formation of new functional groups [9,12]; (5) cell growth tests using plastic as a sole carbon source [10]; and (6) using high-performance liquid chromatography and gas chromatography-mass spectrometry (GC-MS) to monitor chemicals generated from plastic degradation [13]. This section summarizes the highest biodegradation performances achieved by enzymes (Table 1) and microbial strains (Table 2) for fossil-based plastics (polyethylene (PE), polypropylene (PP), polyvinyl chloride (PVC), polyurethane (PU), polyethylene terephthalate (PET), polystyrene (PS), polylactic acid (PLA), and polybutylene succinate (PBS)).…”

“…The degradation of PE and PP is envisioned to occur in three stages: (1) The first stage is the formation of hydrolyzable functional groups in the C-C backbones of PE and PP. Alkane hydroxylases [17] and cytochrome P450 [10] are potential enzymes that can hydroxylate PE and PP to initiate biodegradation (Figure 2 and Table 1) [51]. In addition, enzymes including Baeyer-Villiger monooxygenases, alcohol dehydrogenases, and aldehyde dehydrogenases can contribute to increasing the proportion of oxygen in the backbone of PE and PP [8].…”

“…However, very few reports exist on successful plastic degradation to a degree where these materials can serve as a sole carbon source in metabolic pathways. In a recent study, the Bacillus thuringiensis JNU01 strain, isolated from a landfill site, was identified to grow from an OD600 (optical density at 600 nm) of 0.2 to 1 after 30 days in M9 minimal medium containing PE powder as a sole carbon source (Table 1) [10]. GC-MS analysis of the culture medium identified the production of PE degradation products, including C7-C29 alkanes, C9 alkene, C11 acid, C6 alcohol, and C11-C15 ethers.…”

Significantly Tunable Foaming Behavior of Blowing Agent for the Polyethylene Foam Resin with a Unique Designed Blowing Agent System

“…Polyethylene (PE) is a commonly used plastic material with a wide range of applications. − The research studies of PE have also received extensive attention for its synthesis, modification, − application, − degradation, , etc. Foaming technology has been widely applied in PE products, such as injection foaming and rotational foaming. − The foaming behavior directly affects the performance of the PE foaming products.…”