Microbial enzymes for the biodegradation of polylactic acid (PLA): molecular docking simulation and biodegradation pathway proposal

Polylactic acid (PLA), as a biodegradable polymer, finds widespread utility across diverse sectors, encompassing transportation, agriculture, biomedicine, textiles, electronics, and food packaging. Nonetheless, its degradation kinetics exhibit significant environmental sensitivity, necessitating the development of novel biotechnological methodologies to investigate the microbial and enzymatic constituents implicated in PLA biodegradation. In this review, molecular docking simulations are discussed to analyze the enzymatic degradation of PLA using specific enzymes: proteinase K, PLA depolymerase, and lipase. The binding energy, binding affinity, and dimensions of PLA-binding sites within the enzyme cavities have been examined for each enzyme. The binding amino acid residues mainly include serine, histidine, and aspartate for all plastics, while the interactions involve Van der Waals forces, conventional hydrogen bonding, carbon-hydrogen bonding, and Pi-interactions. Based on our synthesis of the literature, a theoretical PLA biodegradation pathway that illustrates the interaction pattern between PLA and the enzymes, as well as the degradation mechanism is proposed. Our review indicates that in natural environments, enzymes work synergistically, utilizing their unique properties to facilitate an efficient sequential catalytic process for PLA degradation. This integrative approach elucidates the mechanistic underpinnings and metabolic cascades governing PLA degradation, enriching insights into enzymatic catalysis and microbial enzyme-mediated plastic biotransformation. Consequently, a comprehensive understanding of these processes is paramount in optimizing biodegradation kinetics and enhancing the environmental performance of biodegradable polymers. This review provides a detailed framework for refining PLA management strategies and advancing sustainable polymer utilization.