Genetically engineered cyanobacteria remove over 90 percent of microplastic particles from wastewater within one hour while simultaneously cleaning nitrates, ammonia and phosphates. Researchers at Texas A&M University published the method in Nature Communications in December 2025. Wastewater treatment plants could for the first time efficiently retain particles under 500 micrometers, which current filters barely capture.
The orange-peel principle
The trick is biochemically elegant. The cyanobacterium Synechococcus elongatus was genetically engineered to produce limonene, the compound that gives orange peels their characteristic aroma. Limonene is water-repellent (hydrophobic). Since microplastic particles are also hydrophobic, the coated bacteria bind to plastic fragments like magnets. They form clumps that settle and separate from the water phase.
According to the study, the method achieved a removal rate of 91.4 percent for polystyrene particles between 200 and 800 nanometers. Even for the smallest tested particles (200 nanometers) the rate reached roughly 80 percent. This size range is crucial: current wastewater treatment plants barely systematically remove microplastics under 500 micrometers. The collected algae-plastic biomass can also be processed into reinforced bioplastic film, turning the cleanup byproduct into raw material.
Triple action in wastewater
The engineered cyanobacteria do more than catch plastic. According to the study they simultaneously remove 47 to 99 percent of nitrates, nearly 100 percent of ammonia, and nearly all phosphates from wastewater. This nutrient burden is a central problem in modern treatment plants: excess nitrogen and phosphorus in discharge water promotes algal blooms in rivers and lakes, which can harm ecosystems long-term.
The combination of microplastic removal and nutrient cleaning in a single biological process sets this approach apart from current methods relying on physical filtration or chemical flocculants. According to a cost analysis by the research team, production costs run about 3.58 US dollars per kilogram of algal mass. When operated on renewable energy, the entire process would be net carbon-negative.
In context: Other approaches to microplastics
Microplastic removal is an active research field with various competing methods.
Magnetic nanoparticles that bind to plastic fragments and can then be pulled from water using magnetic fields achieved cleanup rates up to 85 percent in studies. The drawback: the nanoparticles themselves must be completely removed from the water, which is technically demanding and costly. Moreover the method works far worse on particles under one micrometer than the cyanobacteria method.
Biological cleaning via natural biofilms in existing wastewater plants today captures part of larger microplastic particles as a side effect in activated sludge flocs. Direct intervention in the process, as engineered algae would allow, is currently absent. For smallest particles under 500 nanometers, where health risks are discussed, there is currently no established cleanup path in municipal treatment plants.
The cyanobacteria method fills precisely this gap. The fact that it simultaneously draws nutrients from water makes it doubly interesting for plant operators: it would merge two currently separate cleaning steps in a single biological system.
What treatment plants would need to deploy this
The path from lab publication to wastewater plant is long. Three prerequisites remain.
First, the method must be tested under real wastewater conditions. Lab work uses defined plastic particles; actual wastewater contains thousands of different plastic types, surfactant and pharmaceutical residues and biological material that can affect the bacteria.
Second, the engineered cyanobacteria must pass European genetic engineering regulation. Use of living genetically modified organisms in treatment plants falls under EU Directive 2009/41/EG on the contained use of GMOs. Approval procedures are time-consuming and vary country to country.
Third, scaling is the classic bottleneck in biotechnology. A reactor system for a mid-size treatment plant handling hundreds of thousands of cubic meters of wastewater daily would be orders of magnitude more complex than the lab setup. The research team estimates pilot plants are realistic from 2028 onward if sufficient funding flows.
Since the EU decision in 2023 to gradually ban intentional microplastic addition to many products, microplastics are a regulatory priority. Demand for wastewater cleaning technologies capturing smallest particles will grow. The laboratory result from Texas A&M is the necessary first step. How far the last step remains depends on how quickly pilot projects follow.