Biodegradation of poly(ethylene terephthalate) through PETase surface-display: From function to structure

Polyethylene terephthalate (PET) is one of the most used plastics which has caused some environmental pollution and social problems. Although many newly discovered or modified PET hydrolases have been reported at present, there is still a lack of comparison between their hydrolytic capacities, as well as the need for new biotechnology to apply them for the PET treatment. Here, we systematically studied the surface-display technology for PET hydrolysis using several PET hydrolases. It is found that anchoring protein types had little influence on the surface-display result under T7 promoter, while the PET hydrolase types were more important. By contrast, the newly reported FAST-PETase showed the strongest hydrolysis effect, achieving 71.3% PET hydrolysis in 24 h by pGSA-FAST-PETase. Via model calculation, FAST-PETase indeed exhibited higher temperature tolerance and catalytic capacity. Besides, smaller particle size and lower crystallinity favored the hydrolysis of PET pellets. Through protein structure comparison, we summarized the common characteristics of efficient PET-hydrolyzing enzymes and proposed three main crystal structures of PET enzymes via crystal structural analysis, with ISPETase being the representative and main structure. Surface co-display of FAST-PETase and MHETase can promote the hydrolysis of PET, and the C-terminal of the fusion protein is crucial for PET hydrolysis. The results of our research can be helpful for PET contamination removal as well as other areas involving the application of enzymes. SYNOPSIS: This research can promote the development of better PET hydrolase and its applications in PET pollution treatment via bacteria surface-display.