16. Role of Microbial Enzymes and Their Modification for Plastic Biodegradation

Plastic waste production is a significant global environmental issue that poses a threat to the health and survival of living organisms. The responsible management of these plastics is a significant challenge in the twenty-first century. Various plastic polymers have been developed over the past 150 years, replacing traditional materials like metal, glass, and wood in different applications. However, the nonreactive and nondegradable nature of plastic has resulted in a massive increase in plastic waste generation, causing serious environmental problems. Plastic waste accumulates in landfills, contaminates the soil, and contributes to increased greenhouse gas emissions. These are some of the harmful effects observed. It is essential to address this ecological problem due to the negative impact of plastic pollution on terrestrial ecosystems. Conventional methods of plastic waste disposal, such as incineration, landfilling, and recycling, have environmental drawbacks. Some synthetic plastics, such as polyethylene terephthalate, polyurethane, polystyrene, polypropylene, and polyvinyl chloride, have chemical structures, molecular weights, and degrees of crystallinity that make them highly resistant to natural biodegradation processes. Enzymes produced by microbes have long been considered a potential biological agent for the biodegradation of plastics; these enzymes can facilitate the hydrolysis or oxidation of polymer bonds, resulting in the formation of less complex and less harmful chemicals. Numerous microorganisms, particularly fungi and bacteria, have been isolated and characterized for their ability to degrade plastics under laboratory conditions. Some of the enzymes involved in plastic biodegradation have been identified and cloned, and their mechanisms of action have been elucidated. Furthermore, genetic engineering and protein engineering techniques have been employed to modify and enhance the activity, specificity, and stability of these enzymes. This chapter provides an overview of the current knowledge on the role of microbial enzymes and their modifications for plastic biodegradation and discusses the challenges and opportunities for the role of microbial enzymes and their modifications for plastic biodegradation.