Biological conversion of multilayer flexible packaging into chemical feedstocks

Problem: Mixed and multilayer plastic packaging is difficult to valorize because different polymers, additives, dyes, plasticizers, and contaminants must be processed together. A technology that can selectively break down multiple polymers and recover useful chemical building blocks could provide a new pathway for end-of-life packaging.

Technology: Our NSF-funded research has identified a bacterial consortium of three Pseudomonas and two Bacillus strains that cooperatively degrade both polyethylene terephthalate (PET) and polyethylene (PE). The consortium's pangenome contains approximately 250 enzymes associated with degradation of biopolymers, synthetic polymers, including PET, PE, PLA, PUR, PVA, PHA and PHB, plasticizers, and related compounds, suggesting broad activity against complex waste streams.

We have demonstrated chemical recovery from both PET and PE. For PET, we combine chemical glycolysis with microbial conversion and low-energy product recovery. In a 30-L static-batch process, our biocatalyst converted PET bottles and enabled recovery of terephthalic acid (TPA) at approximately 90% purity and 60% yield. We have also recovered TPA from multilayer PET material in a mixed-plastic environment. For PE, we have demonstrated synergistic bacterial degradation and recovery of multiple chemical products, with 13% material weight loss during a three-week proof-of-concept experiment. The biological process operates at approximately 30 °C and neutral pH and can use relatively low-cost process inputs. We have confirmed polymer modification and degradation using electron microscopy, ATR-FTIR, HPLC, and GC/MS. We have also identified candidate polymer-degrading enzymes, including a PETase and a cytochrome P450 reductase with activity against PE.

Proposed Solution: We propose using this bacterial consortium, combined with appropriate abiotic pretreatment, to valorize mixed and multilayer packaging. The consortium could simultaneously attack different polymers and selected plasticizers or other organic components, releasing carbon that can subsequently be captured as higher-value chemical products. Rather than requiring complete separation of the waste stream, this approach could provide a biological conversion step for materials that are difficult to recycle by conventional methods.

Proof of Concept: A corporate partner would provide representative difficult-to-recycle multilayer packaging. Over six months, we will determine: (1) the fraction of material converted; (2) which polymers are preferentially degraded; (3) which value-added chemicals are generated and recoverable; (4) the biological and process bottlenecks limiting conversion and product recovery; and (5) the potential for process scale-up.

Packaging will undergo defined pretreatment and then be incubated with the bacterial consortium for 2–3 weeks. Conversion will be quantified by weight loss and polymer analysis, while released products will be identified and quantified by HPLC and GC/MS. The most commercially promising products will be prioritized for recovery and process optimization.

Deliverables: Quantified conversion of representative multilayer packaging Identification of biological and process bottlenecks Optimized consortium performance on packaging waste Measurement of carbon flow from plastic to recovered products Demonstration of one or more value-added chemical products Assessment of scale-up potential and next development steps