About This Project

Developing plastic-degrading enzymes that function at marine conditions would allow us to use them directly in the ocean, breaking down existing plastic waste, converting it into useful metabolites and/or inert compounds, and beginning to reverse the detrimental effects that plastics have had on our marine ecosystems. This project proposes the first step in doing just that- the adaptation of plastic hydrolases for optimized activity and stability at marine conditions for in situ bioremediation.

Ask the Scientists

What is the context of this research?

Plastic accumulation in our oceans poses a significant threat to the health of marine ecosystems and humans (1). Plastic pollution rates are currently around 0.7 million metric tons (Mt)/year and predicted to reach 60 million Mt/year by 2030 (2,3). This plastic pollution contributes to biodiversity loss, resulting in irreparable damage to the stability of aquatic ecosystems and the oceans (4,5). Even the most ambitious waste reduction efforts will not prevent further marine plastic accumulation and strategies to remove the plastic will be essential to restoring the health of our oceans (6). However, physical removal is infeasible due to the quantity, small particle size, and distribution of plastic waste, and such a cleanup project would be incredibly cost and energy intensive (7).

What is the significance of this project?

An eco-friendly alternative to physically removing marine plastics is in situ enzymatic degradation, which would produce significantly less emissions and not require further waste management. While natural plastic biodegradation does happen, the time-scales are too slow to significantly reduce plastic contamination levels (8). Several of the organisms and their enzymes responsible for this degradation have been identified (9,10). The capabilities of these hydrolases to degrade plastic have been demonstrated in the lab setting, but most require non-ambient conditions, such as high temperatures, for reasonable efficiencies (10). These enzymes could provide a solution to marine plastic pollution at a global scale if they can be engineered for high stability and activity at marine conditions.

What are the goals of the project?

Initial efforts should focus on poly(ethylene terephthalate) (PET) degradation with PETase, as it is well characterized and functions at moderate temperatures (11,12). The optimized PETases should be at least as stable and active as the leading PETases: HotPETase (13), FAST-PETase (14), DuraPETase (15), and others (16), but at marine conditions. Based on current literature, these marine-optimized enzymes should be active for at least 10 days at 10-30°C, pH 8-9, and 35-37 practical salinity units (PSU) (17,18) and achieve at least 15% conversion (15) for PET up to 30% crystallinity (19). However, determining specific activity benchmarks will first require quantification of the catalytic rates of the current PETases since their activities are reported as the amount of monomer produced.