Engineered enzyme platform for energy-efficient enzymatic PLA recycling without base addition
A research-led approach to eliminating pH correction in enzymatic PLA depolymerisation. By engineering enzymes to tolerate acid accumulation, this method removes the need for sodium hydroxide dosing, significantly lowering the energy cost and environmental footprint of industrial PLA recycling compared to current PET-based processes.
Overview
Enzymatic hydrolysis offers a mild, sustainable route for recycling polyesters such as polylactic acid (PLA), but industrial application is hampered by the continuous addition of sodium hydroxide (NaOH) needed to neutralise the acid produced during ester bond cleavage. NaOH itself carries a significant production energy footprint, undermining the environmental benefits of biocatalytic recycling. This research proposes that pH correction can be minimised or eliminated entirely through the use of appropriately engineered enzymes operating under tailored conditions, delivering a more energy-efficient process for PLA depolymerisation.
The work is particularly relevant because PLA contains roughly 33% more ester bonds per unit mass than PET, meaning base demand and associated sustainability penalties are even higher for PLA than for the most established enzymatic polyester recycling process. Removing or drastically reducing this base requirement directly addresses a key cost and environmental bottleneck highlighted in published technoeconomic analyses and life cycle assessments.
Technical specifications
Core concept:
- Engineered enzymes capable of depolymerising PLA at industrially relevant loadings (20% w/v suspensions and above) without continuous NaOH dosing
- pH-monitored bioreactor operation to track acid accumulation and enzyme tolerance
- Lactic acid monomer recovery as the primary product stream
Research approach:
- Enzyme variants drawn from an in-house library, expressed in microbial hosts and purified by aqueous chromatography
- Screening of multiple enzyme variants and reaction conditions for high-yield, base-free PLA deconstruction
- Stability and durability testing of selected enzymes under target depolymerisation conditions
- Characterisation of flexible PLA feedstocks using differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA)
- Time-course monitoring of lactic acid production by high-performance liquid chromatography (HPLC)
- Confirmation of final depolymerisation extent by total solid mass loss
- Assessment of lactic acid product quality by nuclear magnetic resonance (NMR) spectroscopy
Technology readiness level
The research is at an early-to-mid stage of laboratory validation. Enzyme engineering, biorecycling, and polymer analysis capabilities are established within the Centre for Enzyme Innovation (CEI), which has a strong track record in engineering enzymes for polyester depolymerisation. The current programme focuses on demonstrating proof-of-concept that PLA can be deconstructed to lactic acid at industrially relevant loadings without base addition. Further work is required to scale the process, validate long-term enzyme durability under continuous operating conditions, and confirm technoeconomic and life cycle advantages at pilot scale. Detailed validation procedures are available under NDA.
About University of Portsmouth
The University of Portsmouth is a modern public research university with an applied, industry-engaged profile. University-managed incubation hubs and coworking facilities connect companies to prototyping spaces, labs, mentorship, and placement-year talent. Partnerships with regional NHS providers and proximity to the Solent maritime and defense cluster enable clinical collaboration and access to real operating environments. Research is supported by competitive funding from UKRI councils, Innovate UK, and NIHR. A dedicated technology transfer office supports IP, licensing, and spinouts with flexible contracting for sponsored R&D.
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