Chapter 9 - Biodegradability and bioremediation of polystyrene-based pollutants: An overview of biological degradation of polystyrene and modified polystyrene for future studies

Abstract

Polystyrene (PS)-based pollutants have been a global environmental concern for many years, primarily from their increasing accumulation and difficult degradation. PS waste can be destroyed by incineration, although that approach releases air pollution and forms hazardous, even mutagenic, by-products. Therefore, biodegradation and bioremediation are considered the best degradation solutions. This chapter focuses on the biodegradation of PS and modified PS, such as expanded PS (trade name Styrofoam) and extruded PS. We also discuss the reasons for the difficult and slow biodegradability of these products. We review known biodegradation methods using various approaches depending on the tool used. Since the 1970s, the microbial biodegradation of PS has been performed with bacteria derived from various sources, such as soil, water, and contaminated sites, e.g., landfills and plastic waste dumps. Studies have found that microorganisms, along with fungi and archaea, can degrade PS with their extracellular or intracellular enzymes. Thanks to the secreted enzymes, PS is a substrate that enables them to grow, breaking PS down into smaller molecular fragments. PS biodegradation by the above-described organisms has been slow to date, and scientists continue to search for more efficient tools to accelerate its pace. Recently, PS biodegradation by the larvae of insects, such as Tenebrio molitor, Tenebrio obscurus, Zophobas atratus, Uloma sp., and Plesiophthalmus davidis, the larvae of the moth Galleria mellonella, and the snail Achatina fulica has been studied, and promising PS biodegradation performance has been observed. At the same time, numerous enzymes that can depolymerize PS have been discovered in the microbial strains of insect guts and probably play a key role in PS biodegradation. Determining and isolating microbial strains is essential, as manufactured PS waste pollutants are widespread. At the end of the chapter, we summarize the advantages and implications of PS biodegradation and describe future perspectives for studies on the biological degradation of PS and modified PS.