Genetically engineered cyanobacteria remove over 90 percent of microplastic particles from wastewater within an hour while simultaneously cleaning nitrates, ammonia, and phosphates. Researchers from Texas A&M University published the method in December 2025 in Nature Communications. Wastewater treatment plants could for the first time efficiently retain particles under 500 micrometers, which conventional filters barely capture.
The orange peel principle
The trick is biochemically elegant. The cyanobacterium Synechococcus elongatus was genetically modified to produce limonene, the substance that gives orange peels their characteristic aroma. Limonene is water-repellent (hydrophobic). Because microplastic particles are also hydrophobic, the coated bacteria bind to plastic particles like magnets. They form clumps that sink 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 at the smallest tested particles (200 nanometers), the rate remained around 80 percent. This size range is crucial: current treatment plants barely systematically remove microplastics under 500 micrometers. The collected algae-plastic biomass can also be further processed into reinforced bioplastic films, turning the waste product of cleaning 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 load is a central problem in modern treatment plants: excess nitrogen and phosphorus in discharge water promotes algal blooms in rivers and lakes, potentially damaging ecosystems long-term.
The simultaneous microplastic removal and nutrient cleaning in a single biological process distinguishes this method from previous approaches relying on physical filtration or chemical flocculants. According to an economic analysis by the research team, production costs are approximately 3.58 US dollars per kilogram of algal biomass. Operated with renewable energy, the entire process would be net carbon-negative.
By comparison: other approaches to microplastics
Microplastic removal is an active research field with various competing methods.
Magnetic nanoparticles that bind to plastic particles and can then be pulled from water using magnetic fields achieved removal rates up to 85 percent in studies. The disadvantage: the nanoparticles themselves must be completely removed from the water, which is technically demanding and costly. Additionally, the method performs far worse on particles under one micrometer than the cyanobacteria approach.
Biological cleaning through natural biofilms in existing treatment plants today captures some larger microplastic particles as a side effect in activated sludge flocs. Direct intervention in the process, as genetically modified algae would enable, is currently missing. For ultra-small particles under 500 nanometers, where health risks are debated, there is currently no established removal path in municipal treatment plants.
The cyanobacteria method closes precisely this gap. That it simultaneously removes nutrients from water makes it doubly interesting for treatment plant operators: it would combine two previously separate cleaning steps in one biological system.
What treatment plants would need to use this
The path from laboratory publication to treatment plant is long. Three prerequisites are still missing.
First, the method must be tested under real wastewater conditions. In the laboratory, one works with defined plastic particles; actual wastewater contains thousands of different plastic types, surfactant and pharmaceutical residues, and biological material that could affect bacteria.
Second, the genetically modified cyanobacteria must pass European genetic engineering regulations. Using living genetically modified organisms in treatment plants falls under EU Directive 2009/41/EG on contained use of GMOs. Approval procedures are time-consuming and vary country to country.
Third, scaling is the classic bottleneck in biotechnology. A reactor installation for a medium-sized treatment plant handling hundreds of thousands of cubic meters of wastewater daily would be orders of magnitude more complex than the laboratory setup. The research team estimates that pilot installations are realistic by 2028 if adequate funding flows.
Microplastics have been a regulatory priority since the EU's 2023 decision to gradually ban intentional addition of microplastics to many products. Demand for wastewater treatment technologies that capture ultra-small particles will rise. The laboratory result from Texas A&M is the necessary first step. How far the final step remains depends on how quickly pilot projects follow.