In an innovative breakthrough, scientists have tapped into the potential of genetically modified cyanobacteria to tackle the pervasive issue of microplastic pollution. This novel method utilizes an unlikely hero: a fragrant molecule known as limonene, renowned for its citrus aroma, to bind and remove microplastics from the environment.
The issue of microplastics has become nearly inescapable, with these tiny particles being discovered in various ecosystems, including human bodies, oceans, and potable water sources. The debate rages on regarding their true health impact, but one thing is clear: detecting microplastics has become easier due to advances in analytical chemistry. Traditional methods for their removal are often costly and impractical for large-scale operations.
Enter a cutting-edge strategy that merges genetic engineering with chemistry, promising a more efficient solution. This research, conducted by Professor Susie Dai and her team at Texas A&M University, was recently published in Nature Communications. Their study reveals how algae can be genetically modified to produce limonene, which exhibits properties favorable to capturing microplastics without the need for harsh chemicals or complex filtration systems.
Engineering Algae with a Scent
The research involved the insertion of the limonene synthase gene directly into the DNA of cyanobacteria. This genetic tweak enables the bacteria to generate significant amounts of limonene, a substance that is not only aromatic but also effective at attracting microplastics.
This process is steeped in complex molecular biology, involving intricate mechanisms like transcriptional regulation and ribosomal function. However, the essence of the method is straightforward: the algae are genetically programmed to produce limonene, which then acts to gather microplastics together.
The Role of Limonene
Limonene is a versatile hydrocarbon that shares properties with paint thinners; it dissolves oils and resins effectively while remaining insoluble in water. This nonpolar nature allows it to interact with microplastics, which are similarly nonpolar. The similarity to turpentine, another terpene-based solvent, underscores limonene’s capability in tackling plastic waste.
Figure 1. Selected properties of limonene. Although the two enantiomers differ in scent (orange vs. lemon), they have identical physical properties, including low water solubility. That’s no coincidence: enantiomers always have identical boiling points, melting points, and solubilities.
Mechanism of Action
The method relies on the cultivation of these engineered cyanobacteria in controlled environments such as photobioreactors or managed ponds. Here, they utilize sunlight and CO₂ for growth. These modified cells develop hydrophobic surfaces due to the high limonene content.
When water containing microplastics is introduced, the limonene-coated algae bind with the plastic particles, forming aggregates. These clumps, once large enough, settle to the bottom due to gravity. This sediment, a mix of algae and plastic, is collected, allowing the now-clear water to be either released or further processed.
This innovative approach bypasses the need for expensive filtration systems by making microplastics adhere to larger particles that naturally sink. It’s a practical application of surface chemistry and synthetic biology, offering a promising route to mitigate microplastic pollution.
Source: Remediation and upcycling of microplastics by algae with wastewater nutrient removal and bioproduction potential. Nature Communications DOI:10.1038/s41467-025-67543-5
Original Story at www.acsh.org