Degradation of Low-Density Polyethylene by Physical, Chemical, and Microbial-Based Approaches

Plastics have emerged as an indispensable source in modern lifestyles due to their durability, lightweight, adaptability, and cost-effectiveness. Many forms of synthetic polymers, like polyethylene, polystyrene, and polypropylene, are used practically in all fields today, along with other developed polymers. However, plastic pollution has become a significant hurdle in environmental pollution, whether air, water, or soil. Studies reveal that microbes can utilize low-molecular-weight molecules and are not constructively developed for high molecular-weight molecules. There have been various claims and studies targeting the degradation of plastic in various habitats, ranging from a few hundred to thousands of years. However, these claims are not explicit due to the lack of various scientific evidence and extrapolation methods. The present chapter focuses on the latest perspectives on plastic degradation, especially low-density polyethylene (LDPE), by physical, chemical, and biological methods. The various physical and chemical factors that affect the degradation of plastic will be discussed in this chapter. Abiotic factors like air, moisture, radiation, temperature, and light contribute to the stress on the plastic surface. The major measurable parameters, such as the hydrophobicity of the surface, its molecular weight, and the impact of functional groups, have a significant role in plastic degradation. There is a free radical formation, which, in the presence of oxygen may form peroxides and hydroperoxides, leading to oxidative degradation. Regarding the biotic factor, biofilm formation plays a major role in plastic degradation. The chapter comprehensively highlights the role of various microorganisms and their biofilm in LDPE degradation and their metabolic pathways. A detailed discussion on the applications of microbial enzymes will also be highlighted. The chapter is an updated aspect of physical, chemical, and microbial-based degradation of plastic polymers.