Transforming Poly(butylene adipate-<i>co</i>-terephthalate) into Protocatechuic Acid via Enzymatic Degradation and Whole-Cell Catalysis

Poly(butylene adipate-<i>co</i>-terephthalate) (PBAT) is a biodegradable plastic with increasing applications that degrades rapidly in composting, but its sole degradation limits residual value utilization. Therefore, new strategies for converting PBAT to valuable products are needed. In this study, enzymatic degradation was applied to hydrolyze PBAT, and an engineered <i>Escherichia coli</i> strain was constructed and utilized as a whole-cell catalyst to synthesize protocatechuic acid (PCA), a valuable platform compound, from degradation products. By fine-tuning the overexpression of four enzymes in the biosynthetic pathway and optimizing catalytic conditions, the titer of PCA was increased 5.07-fold to 5.28 ± 0.05 g/L, achieving a 15.45 ± 1.04 wt % conversion rate from pure PBAT particles. Furthermore, the strategy was applicable to commercial PBAT/poly(lactic acid) (PLA), achieving a maximum conversion rate of 25.05 ± 1.21 wt %. Thus, a novel strategy to utilize the PBAT waste was established, which provides a reference for upgrading other macrowaste resources.