PET as a substrate for microbial upcycling

Ideonella sakaiensis is able to survive on poly(ethylene terephthalate) (PET) as its sole carbon source and completely metabolizes it to produce CO2 and water. I.sakaiensis has also been reported to ferment poly(ethylene terephthalate) (PET) to produce ethanol and acetate. The bacterium secretes PETase, a PET-degrading enzyme, which is able to degrade even highly crystalline PET, but the bacterium's ability to survive on crystalline PET is unclear. In order to replicate this fermentation behaviour, I.sakaiensis was cultured anaerobically on commercially available semi-crystalline PET as well as ethylene glycol. No acetate or ethanol production was observed in either case. I.sakaiensis' aerobic growth on PET of varying crystallinities was also monitored over time to determine its ability to access crystalline PET. Surprisingly, I.sakaiensis was able to grow on both commercially available semi-crystalline PET and amorphous films at a similar rate. Cultures varied widely, however, leading to the possibility of selecting strains that can better access crystalline PET. Ongoing trials of anaerobic growth will use I.sakaiensis that has been adapted to grow in minimal media on PET prior to inoculation in anaerobic cultures, hopefully leading to acetate and ethanol production. These value-added chemicals are useful as final end products, as well as for continued conversion through engineering or coupling with other bacteria.