Biodegradation of PET plastic by a marine strain Rhodococcus pyridinivorans P23 with a membrane anchoring PET esterase in a biofilm model

Abstract Evidence for microbial biofilm formation on polyethylene terephthalate (PET) has previously been reported, but little is known about the PET biodegradation process and molecular mechanism by biofilm especially in marine environments. Here, we isolate a PET-degrading bacterium, Rhodococcus pyridinovorans P23, from deep sea sediment with the ability to grow using PET as sole carbon and energy source. We identify a novel membrane anchoring PET degrading enzyme dubbed PET esterase through activity tracking, and find that in addition to depolymerizing PET, it also hydrolyzes MHET into TPA under acid conditions. We prove that it is a low and constitutive transcribed transmembrane protein displaying on the cell surface ensuring no loss into the ocean. Based on these findings, we propose a PET biodegradation model with microbial biofilm formation in marine environment. The crucial roles of biofilm is retaining degradation product MHET and TPA to create an acidic microenvironment on the PET plastic surface distinguishing itself from the alkaline sea water, which promotes the MHET hydrolysis by PET esterase to produce TPA for utilization. Furthermore, we also investigate the microbial groups possessing PET esterase coupled with TPA degradation pathway mainly in phyla Proteobacteria and Actinobacteriota.