Microbial Upcycling of Waste PET to Adipic Acid

Abstract

Microorganisms can be genetically engineered to transform abundant waste feedstocks into value-added small molecules that would otherwise be manufactured from diminishing fossil resources. Herein, we report the first one-pot bio-upcycling of PET plastic waste into the prolific platform petrochemical and nylon precursor adipic acid in the bacterium Escherichia coli. Optimizing heterologous gene expression and enzyme activity enabled increased flux through the de novo pathway, and immobilization of whole cells in alginate hydrogels increased the stability of the rate-limiting enoate reductase BcER. The pathway enzymes were also interfaced with hydrogen gas generated by engineered E. coli DD-2 in combination with a biocompatible Pd catalyst to enable adipic acid synthesis from metabolic cis,cis-muconic acid. Together, these optimizations resulted in a one-pot conversion to adipic acid from terephthalic acid, including terephthalate samples isolated from industrial PET waste and a post-consumer plastic bottle.