Introduction: Low-density polyethylene (LDPE) is one of the most widely used materials today. Unfortunately, LDPE has slow degradation after disposal, which lead to environmental pollution and endangering ecosystems. Therefore, we need effective methods to reduce LDPE pollution in our environment. Biodegradation by microorganisms is a green approach that can help address this issue. In this overview, we will present the roles of some Pseudomonas aeruginosa species in LDPE degradation.
Methods: As plastic usage has increased, the issue of post-consumer recycling has gained significant importance. Low-density polyethylene (LDPE) is a linear hydrocarbon polymer composed of long chains of ethylene monomers (C2H4) and constitutes a substantial portion of plastic waste. The degradation of low-density polyethylene (LDPE) in natural environments is a slow process which influenced by various environmental factors, including pH levels, atmospheric moisture, humidity, temperature, and exposure to solar radiation.
The utilization of landfills may be viewed as a viable strategy; however, it comes with specific constraints. These constraints include an extended period required for decomposition and the discharge of harmful pollutants recognized to be linked to various human illnesses, notably cancer. therefore, microorganism biodegradation’s ability gives us the chance to degrade plastic waste with fewer harms.
Results: Among the biodegradation methods, bacterial usage is one of the effective ways to control the problem. Pseudomonas aeruginosa is a Gram-negative bacterial species belonging to the Pseudomonadaceae family in the Gammaproteobacteria class, and it is one of the most commonly reported bacteria for this purpose.
One of the reports about Pseudomonas aeruginosa includes the ISJ14 strain, which was isolated from a waste dump and demonstrated biodegradation ability at 37 °C without causing any danger to human health and the environment.[1]
Pseudomonas aeruginosa E7 strain is another bacterium isolated from beach soil, which was previously contaminated by oil spills. The degradation system consists of alkane hydroxylase genes, such as rubredoxin reductase, rubredoxin, and alkane monooxygenase.[2]
Another study reports on P. aeruginosa isolated from the surface water of Yaounde, showing the ability to degrade materials under acidic pH conditions and at low temperatures (7°C and 23 ± 1°C) in the environment.[3]
In the research conducted by Kyaw et al., they studied four bacterial strains, two of which belonged to the Pseudomonas aeruginosa species. They assessed the abilities of Pseudomonas aeruginosa (PAO1) and Pseudomonas aeruginosa (ATCC) strains using different methods. After a 120-day incubation period, weight loss measurements were recorded, with Pseudomonas aeruginosa (PAO1) strain demonstrating a 20% reduction in weight, while Pseudomonas aeruginosa (ATCC) strain showed an 11% reduction.
They assessed the Mechanical Properties through extension at break (EAB) and initial tensile strength (TS) measurements after 120 days of incubation. For Pseudomonas aeruginosa PAO1, the EAB measurement showed a reduction to 79 mm ± 3%, while the TS reduced to -0.00078 ± 0.00011 MPa. In the case of Pseudomonas aeruginosa ATCC, the EAB measurement decreased to 92 mm ± 3%, and the TS reduced to 0.00026 ± 0.0002 MPa. They also assessed structural changes using Fourier Transform Infrared (FTIR). Pseudomonas aeruginosa PAO1 caused an 80% reduction, while Pseudomonas aeruginosa ATCC resulted in a 16% reduction.[4]
Dwicania et al. conducted a study on a bacterial mixture consisting of Brevibacterium sp. and Pseudomonas aeruginosa and their impact on Linear Low-Density Polyethylene (LLDPE). The mixed culture was obtained from the Biology/Environmental Microbiology Laboratory at the Environmental Engineering Department of Trisakti University. They analyzed the effect of the mixture on LLDPE using Fourier Transform Infrared (FTIR), which revealed a reduction in intensity.[5]
Conclusion: Pseudomonas aeruginosa is one of the successful bacteria in LDPE biodegradation. Different study results have shown a reduction in the physical and biochemical LDPE samples. Although some genes and pathways that are involved in LDPE biodegradation are known today, we need more studies to understand the molecular mechanisms.
1)doi.org/10.1016/j.heliyon.2020.e04398
2)doi.org/10.1016/j.ibiod.2015.04.024
3)doi.org/10.1016/j.envc.2021.100056
4)doi: 10.1007/s12088-012-0250-6
5)doi:10.1088/1742-6596/1402/2/022105