Using 3D-printed cyanobacteria to clean water

A team of US researchers has mixed a seaweed extract with a genetically engineered bacteria to create a substance which can break down common pollutants.  

Their “engineered living material” is designed to decontaminate water – but the researchers say they could program the bacteria to do other tasks, too. Another benefit – the substance can be mixed in a 3-D printer.

The material is made by mixing alginate, a carbohydrate polymer found in seaweed, with water-dwelling cyanobacteria.

They fed this mixture to a 3D-printer, and turned it into a variety of structures – the researchers found that a grid worked best, because it kept the photosynthetic cyanobacteria exposed to light and nutrients.

“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,” says Professor Jon Pokorski, a researcher at the University of California, San Diego, US.

The researchers used genetically engineered cyanobacteria which had been designed to make a protein, called laccase. This protein can break down a variety of common pollutants like BPA, dyes, and pharmaceutical drugs.

They showed the material worked by adding it to a mixture containing indigo carmine, which is used to dye denim blue. The material removed all the colour from the solution after several days.

Credit: UC San Diego Jacobs School of Engineering

The researchers also added genes to the bacteria to be vulnerable to a substance called theophylline, which occurs naturally in substances like tea and is also used as a drug to treat asthma.

Theophylline triggers a destruction process in the cyanobacteria, meaning it can be eliminated once it serves its purpose.

“The living material can act on the pollutant of interest, then a small molecule can be added afterwards to kill the bacteria,” says Pokorski.

“This way, we can alleviate any concerns about having genetically modified bacteria lingering in the environment.”

For now, the material will continue to live in a petri dish as the researchers optimise it. They’re hoping to tune their bacteria further, so it can target more pollutants and be destroyed by other things – possibly even becoming self-destroying.

“Our goal is to make materials that respond to stimuli that are already present in the environment,” says Pokorski.

“We’re excited about the possibilities that this work can lead to, the exciting new materials we can create.”

A summary of the research is published in Nature Communications.

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