Microbial fermentation for biodegradation and biotransformation of waste plastics into high value-added chemicals

Petroleum-based synthetic plastics are difficult to be biodegraded due to their large molecular weight, high hydrophobicity, and high chemical bond energy. The increasing accumulation of waste plastic in the environment has resulted in severe “white pollution.” Currently, landfilling and incineration are commonly used for waste plastic disposal. However, life-cycle assessment (LCA) studies indicate that landfilling is the worst end-of-life management option, while incineration is also not a viable solution for plastic pollution due to the considerable release of greenhouse gas and dangerous substances. Therefore, it is urgent to develop a green and efficient recycling technology for waste plastic management. In recent years, studies on plastics biodegradation using microorganisms or enzymes have achieved a breakthrough progress, exhibiting a promising prospect for developing biodegradation and biotransformation technologies toward waste plastics disposal. In this chapter, we comprehensively summarized the microorganisms and enzymes involved in plastics depolymerization, with emphasis on the analysis of the biodepolymerization pathways and degradants derived from specific plastics. In addition, application of these depolymerization products as substrates for high-value added chemicals production is highlighted. Moreover, the obstacles lying on the way for waste plastics biodegradation, including the lack of depolymerases, low depolymerization efficiency, and difficulties against plastic degradants utilization are deeply discussed.