Novel Feruloyl Esterase for the Degradation of Polyethylene Terephthalate (PET) Screened from the Gut Microbiome of Plastic-Degrading Mealworms (<i>Tenebrio Molitor</i> Larvae)

Abstract

Mealworms (<i>Tenebrio molitor</i>) larvae can degrade both plastics and lignocellulose through synergistic biological activities of their gut microbiota because they share similarities in chemical and physical properties. Here, a total of 428 genes encoding lignocellulose-degrading enzymes were screened from the gut microbiome of <i>T. molitor</i> larvae to identify poly(ethylene terephthalate) (PET)-degrading activities. Five genes were successfully expressed in <i>E. coli</i>, among which a feruloyl esterase-like enzyme named <i>Tm</i>Fae-PETase demonstrated the highest PET degradation activity, converting PET into MHET (0.7 mg_MHETeq ·h^-1·mg_enzyme^-1) and TPA (0.2 mg_TPAeq ·h^-1·mg_enzyme^-1) at 50 °C. <i>Tm</i>Fae-PETase showed a preference for the hydrolysis of ferulic acid methyl ester (MFA) in the presence of both PET and MFA. Site-directed mutagenesis and molecular dynamics simulations of <i>Tm</i>Fae-PETase revealed similar catalytic mechanisms for both PET and MFA. <i>Tm</i>Fae-PETase effectively depolymerized commercial PET, making it a promising candidate for application. Additionally, the known PET hydrolases <i>Is</i>PETase, FsC, and LCC also hydrolyzed MFA, indicating a potential origin of PET hydrolytic activity from its lignocellulosic-degrading abilities. This study provides an innovative strategy for screening PET-degrading enzymes identified from lignocellulose degradation-related enzymes within the gut microbiome of plastic-degrading mealworms. This discovery expands the existing pool of plastic-degrading enzymes available for resource recovery and bioremediation applications.