Comprehensive review on enzymatic polymer degradation: A sustainable solution for plastics

Abstract

Synthetic plastics have been present in ecosystems for decades, and the increasing usage of plastic polymers has been a serious environmental challenge. The enzymatic polymer biodegradation, catalyzed by microbes, can address this issue by metabolizing the carbon from the polymer chain and decomposing it into simpler constituents. The key enzymes include hydrolase, lipase, cutinase, and peroxidase produced by diverse microorganisms and are responsible for the biodegradation of polymers. The present review has focused on several techniques of polymer biodegradation facilitated by enzymes through specific modes of action. The impact of enzymatic biodegradation of polymers on environmental sustainability has been thoroughly examined. This involves the microorganisms like fungi and bacteria, which utilize the substrate and depolymerize it. Microorganisms, such as bacterial species Pseudomonas, Bacillus, and Ideonella, release various enzymes. Fungal species, specifically Pseudozyma, Candida, Fusarium, Aspergillus, Penicillium, Rhizopus, and the composite microorganisms involved in the biodegradation of polymers, have been studied extensively. Plastic deterioration occurs through aerobic and anaerobic processes, depending on the oxygen presence or oxygen absence conditions. The aerobic process operates efficiently and achieves total breakdown more rapidly than the anaerobic process. Aerobic degradation generates biogas, a renewable energy source, whereas anaerobic degradation creates methane-like gases, causing environmental issues. Oxidation and hydrolysis are the two reaction types involved in plastic biodegradation. The current investigation examines various plastics, including polyethene, polyurethane, polyethene terephthalate, polystyrene, polypropylene, and polyvinyl chloride, and their biodegradation mechanisms facilitated by different enzymes.