Development and comparative analysis of microbial cell-based and extracellular PET degradation systems

Plastics are widely used in modern industry due to their versatile applications and low production costs, with polyethylene terephthalate (PET) being one of the most commonly preferred polymers, especially in singleuse packaging. In response to the accumulation of PET waste in the environment, an increasing number of microorganisms capable of hydrolyzing ester bonds in PET and facilitating its degradation into smaller, environmentally sustainable by-products have been identified. In this study, both cell-based and cell-free systems were employed to evaluate the biodegradability of PET waste, which is widely distributed in the environment and resistant to natural degradation. The primary objective was to compare the degradation efficiencies of different systems and to analyze the resulting products both quantitatively and qualitatively to assess system performance at the molecular level. Experiments were conducted using 5 mg of PET with high crystallinity (>30%). In the cell-based system, a degradation rate of 1.29% was achieved after 48 hours, with approximately 0.333 mM of terephthalic acid (TPA) and 0.0007 mM of ethylene glycol (EG) detected. In contrast, the cell-free system yielded a 5.39% degradation rate within 24 hours, producing 1.199 mM TPA and 0.0042 mM EG. HPLC analyses and HOTP fluorescence results confirmed TPA formation, while SEM imaging revealed distinct morphological deterioration on the PET surface, especially in the cell-free system. Statistical analysis indicated a significant difference (p < 0.05) in product yields between the two systems, with the cell-free system demonstrating approximately 4.2 times higher efficiency. This difference is attributed to the ability of enzymes to operate in a more controlled environment, free from metabolic side effects and with optimized reaction conditions in the cell-free system. The findings highlight that cell-free systems offer greater efficiency and faster PET biodegradation, primarily due to the controlled conditions and absence of inhibitory effects. While cell-based systems have the advantage of sustained enzyme production, their degradation performance remains limited by cellular metabolic constraints. Overall, the results suggest that cell-free platforms, when further enhanced through advanced engineering approaches, hold strong potential for industrial-scale application in plastic waste bioconversion. Therefore, expanding research and optimization efforts on cell-free systems is essential to support sustainable plastic recycling solutions.