Sustainable bioconversion of synthetic plastic wastes to polyhydroxyalkanoate (PHA) bioplastics: recent advances and challenges

Abstract

Millions of tons of chemical plastics are accumulated annually worldwide in terrestrial and marine environments due to inadequate recycling plants and facilities and low circular use. Their continuous accumulation and contamination of soil and water pose a severe threat to the environment and to human, animal and plant health. There is therefore an urgent need to develop effective eco-environmental strategies to overcome the significant environmental impacts of traditional plastic waste management practises (incineration, landfilling, and recycling). In recent years, reports on microbial strains equipped with the potential of degrading plastic materials, which can further be converted into usable products such as PHA bioplastics have sprung up, and these offer a possibility to develop microbial and enzymatic technologies for plastic waste treatment and then progressing plastics circularity. In this chapter, an overview of the reported microbial and enzymatic degradations of petroleum-based synthetic plastics, specifically polyethylene, polystyrene, polypropylene, polyvinyl chloride, polyurethane and polyethylene terephthalate, is detailed. Furthermore, the harvesting of depolymerization products to produce new PHA materials with high added industrial value can be considered as an innovative solution, helping to increase synthetic plastic recycling rate and creating new circular economy opportunities. Finally, the challenge of ending plastic pollution is still difficult, but sustainable, renewable, bio-based and completely biodegradable, PHA will hold enormous promise for replacing plastics made from petrochemicals.