Microbial-Assisted Degradation of Plastic and Pathways to Resource Recovery

Abstract

Plastic pollution is one of the most challenging environmental issues worldwide, due to massive consumption of plastics and inadequate technologies and policies for degradation and reuse of plastic waste. Traditional waste-management approaches, such as landfills, incineration, and mechanical recycling lack circularity with adverse environmental implications. Microbial-mediated degradation is an environmentally friendly approach to convert plastic waste into nontoxic molecules using lower energy demands. Many organisms have the capacity to colonize plastic surfaces as biofilms and excrete extracellular enzymes to depolymerize plastics and metabolize them for growth and nutrient production. Enzymes [polyethylene terephthalate hydrolase (PETase) and mono-(2-hydroxyethyl) terephthalic acid hydrolase (MHETase), cutinases, lipases, and oxygenases] play a key role to hydrolyze different kinds of plastic through specific metabolic pathways. In this chapter, we highlight the important native microbial species with plastic degradation capabilities and discuss the mechanisms and factors influencing their effectiveness of plastic degradation. Then we present the various biotechnology-based engineering approaches using genetically modified organisms developed to enhance the efficiency of microbial-assisted plastic degradation. We emphasize the role of microbes in transforming plastic into valuable byproducts and as feedstock for bioenergy production, thus, reclassifying plastic as a resource instead of waste. Microbial-assisted plastic conversion and utilization technologies developed for industrial scale and the companies implementing them are presented. We address the challenges encountered in the extensive implementation of microbially assisted plastic conversion, particularly concerning technology, policy, and regulations. We finally identify focus areas for future research aimed at achieving significant advancements in the recovery and reuse of plastic waste.