Potential one-step strategy for PET degradation and PHB biosynthesis through co-cultivation of two engineered...

The management and recycling of plastic waste is a challenging global issue. Polyethylene terephthalate (PET), one of the most widely used synthetic plastics, can be hydrolyzed by a series of enzymes. However, upcycling the resulting monomers is also a problem. In this study, we designed a co-cultivation system, in which PET degradation was coupled with polyhydroxybutyrate (PHB) production. First, PETase from Ideonalla sakaiensis was expressed in Yarrowia lipolytica Po1f with a signal peptide from lipase. The engineered PETase-producing Y. lipolytica was confirmed to hydrolyze bis(2-hydroxyethyl) terephthalate (BHET) and PET powder into the monomers terephthalate (TPA) and ethylene glycol (EG). Simultaneously, a TPA-degrading Pseudomonas stutzeri strain isolated from PET waste was transformed with a recombinant plasmid containing the phbCAB operon from Ralstonia eutropha, which encodes enzymes for the biosynthesis of PHB. The two co-cultivated engineered microbes could directly hydrolyze BHET to produce the bioplastic PHB in one fermentation step. During this process, 5.16 g/L BHET was hydrolyzed in 12 h, and 3.66 wt% PHB (3.54 g/L cell dry weight) accumulated in 54 h. A total of 0.31g/L TPA was produced from the hydrolyzation of PET in 228 h. Although PHB could not be synthesized directly from PET because of the low hydrolyzing efficiency of PETase, this study provides a new strategy for the biodegradation and upcycling of PET waste by artificial microflora.