Microbial-driven circular bioeconomy approaches for sustainable bioplastics management

The growing plastic crisis and the necessity to shift the use of fossil resources have placed bioplastics as central alternatives to other materials in the global environment. These materials, which include polyhydroxyalkanoates (PHA), polylactic acid (PLA), and starch-based polymers, are derived as such that one can reduce carbon footprints as well as provide a viable end-of-life option due to biodegradability. However, without a conscious decision to be circular, the bioplastics will be sent to linear disposal models where, in the end, poor management will result in either contamination of recycling streams or inefficient degradation in an inappropriate environment. This lack of connection highlights the pressing need to incorporate bioplastics into strong Circular economy (CE) models, which would make a major focus on the constant retention of materials within utilisation cycles. This review argues that microorganisms and their enzymatic machineries are the biological catalysts that are needed to make this circular vision of bioplastics a reality. The systematic analysis of the microbial strategies is introduced, which begins with the enzymatic degradation of major classes of biopolymers and characterizes the specificity of depolymerases, cutinases, and hydrolases. The discussion then progresses into the field of microbial upcycling which represents a paradigm shift of treating waste to recovering resources, as bioplastic waste is used to generate value-added products in the form of platform chemicals, solvents, biosurfactants, and even next-generation biopolymers. Additionally, the state-of-the-art improvement with metabolic engineering and synthetic microbial consortia is investigated, which is to be efficient and resilient. The review critically evaluates how these biological processes may be incorporated into scalable CE systems, examines technological readiness, life-cycle, and the necessary synergy between policy, infrastructure and innovation. Finally, it hypothesizes that through adoption of microbial processes, bioplastic waste can be converted into a renewable feedstock, rather than a liability to the environment and thus creating an essential route toward a regenerative, circular bioeconomy.