Two-step biocatalytic conversion of post-consumer polyethylene terephthalate into value-added products facilitated by genetic and bioprocess engineering

Solving the plastic crisis requires high recycling quotas and technologies that allow open loop recycling. Here a biological plastic valorization approach consisting of tandem enzymatic hydrolysis and monomer conversion of post-consumer polyethylene terephthalate into value-added products is presented. Hydrolysates obtained from enzymatic degradation of pre-treated post-consumer polyethylene terephthalate bottles in a stirred-tank reactor served as the carbon source for a batch fermentation with an engineered Pseudomonas putida strain to produce 90 mg/L of the biopolymer cyanophycin. Through fed-batch operation, the fermentation could be intensified to 1.4  g/L cyanophycin. Additionally, the upcycling of polyethylene terephthalate monomers to the biosurfactants (hydroxyalkanoyloxy)alkanoates and rhamnolipids is presented. These biodegradable products hold significant potential for applications in areas such as detergents, building blocks for novel polymers, and tissue engineering. In summary, the presented bio-valorization process underscores that addressing challenges like the plastic crisis requires an interdisciplinary approach.