The novel photosynthetic biocomposite material is a 3D-printed structure made of a seaweed-based polymer combined with genetically engineered cyanobacteria to produce an enzyme that transforms various organic pollutants into benign molecules. The bacteria were also engineered to self-destruct in the presence of a molecule called theophylline, which is often found in tea and chocolate.
Datta et al. developed a ‘living material’ that could offer a sustainable and eco-friendly solution to clean pollutants from water. Image credit: David Baillot / UC San Diego Jacobs School of Engineering.
“What’s innovative is the pairing of a polymer material with a biological system to create a living material that can function and respond to stimuli in ways that regular synthetic materials cannot,” said University of California San Diego’s Professor Jon Pokorski.
To create their novel living material, Professor Pokorski and his colleagues used alginate, a natural polymer derived from seaweed, hydrated it to make a gel and mixed it with a type of water-dwelling, photosynthetic bacteria known as cyanobacteria.
The mixture was fed into a 3D printer. After testing various 3D-printed geometries for their material, the researchers found that a grid-like structure was optimal for keeping the bacteria alive.
The chosen shape has a high surface area to volume ratio, which places most of the cyanobacteria near the material’s surface to access nutrients, gases and light.
The increased surface area also makes the material more effective at decontamination.
As a proof-of-concept experiment, the scientists genetically engineered the cyanobacteria in their material to continually produce a decontaminating enzyme called laccase.
“Laccase can be used to neutralize a variety of organic pollutants including bisphenol A, antibiotics, pharmaceutical drugs and dyes,” they said.
In the present study, the authors demonstrated that their material can be used to decontaminate the dye-based pollutant indigo carmine, which is a blue dye that is widely used in the textile industry to color denim. In tests, the material decolorized a water solution containing the dye.
They also developed a way to eliminate the cyanobacteria after the pollutants have been cleared.
They genetically engineered the bacteria to respond to a molecule called theophylline. The molecule triggers the bacteria to produce a protein that destroys their cells.
“The living material can act on the pollutant of interest, then a small molecule can be added afterwards to kill the bacteria,” Professor Pokorski said.
“This way, we can alleviate any concerns about having genetically modified bacteria lingering in the environment.”
“A preferable solution is to have the bacteria destroy themselves without the addition of chemicals. This will be one of the future directions of this research.”
“Our goal is to make materials that respond to stimuli that are already present in the environment.”
The team’s work is published in the journal Nature Communications.
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D. Datta et al. 2023. Phenotypically complex living materials containing engineered cyanobacteria. Nat Commun 14, 4742; doi: 10.1038/s41467-023-40265-2
