Engineers at MIT and Imperial College London have developed a new way to generate durable, functional materials using a mixture of bacteria and yeast similar to the “mother kombucha” used to ferment tea.
Through this mixture, also called SCOBY (symbiotic culture of bacteria and yeast), the researchers were able to produce cellulose embedded with enzymes that can perform various functions, such as detecting environmental contaminants. They also demonstrated that they could incorporate yeast directly into the material, creating “living materials” that could be used to purify water or to make “smart” packaging materials that could detect damage.
“We anticipate a future where various materials can be grown at home or in local production facilities, using biology instead of resource-intensive centralized manufacturing,” says Timothy Lu, associate professor of electrical and computer engineering and biological engineering. from MIT.
Lu and Tom Ellis, a professor of bioengineering at Imperial College London, are the lead authors of the article, which appears today in Materials of nature. The lead authors of the paper are MIT student Tzu-Chieh Tang and Cambridge University postdoctoral fellow Charlie Gilbert.
Division of labor
Several years ago, Lu’s lab developed a way to use it E. coli to generate biofilms embedded with materials such as gold nanowires. However, these films are very small and thin, making them difficult to use in most large-scale applications. In the new study, researchers set out to find a way to use microbes to generate larger amounts of more substantial materials.
They thought of creating a population of microbes similar to a kombucha mother, which is a mixture of certain types of bacteria and yeast. These fermentation plants, which usually contain one species of bacteria and one or more species of yeast, produce ethanol, cellulose and acetic acid, which gives kombucha tea its distinctive flavor.
Most strains of wild yeast used for fermentation are difficult to modify genetically, so the researchers replaced them with a strain of laboratory yeast called Saccharomyces cerevisiae. They combined yeast with a type of bacterium called Komagataeibacter rhaeticus, which his collaborators at Imperial College London had previously isolated from a kombucha mother. This species can produce large amounts of cellulose.
Because the researchers used a laboratory yeast strain, they could design the cells to do anything the laboratory yeast can do, for example, produce enzymes that glow in the dark or detect contaminants in the environment. Yeast can also be programmed so that it can break down contaminants after they are detected.
Meanwhile, the culture bacteria produce large amounts of hard cellulose to serve as scaffolding. The researchers designed their system so they could control whether the yeast itself or just the enzymes it produces are incorporated into the structure of the cellulose. It only takes a few days to cultivate the material and, if left long enough, it can be thickened to occupy a space as large as a bathtub.
“We think this is a good system that is very cheap and very easy to manufacture in very large quantities,” Tang says. “It simply came to our notice then E.coli system “.
Just add tea
To demonstrate the potential of their microbial culture, which they call “Syn-SCOBY,” the researchers created a material that incorporates yeast that detects estradiol, which is sometimes found as an environmental pollutant. In another version, they used a yeast strain that produces a bright protein called luciferase when exposed to blue light. These yeasts could be exchanged for other strains that detect other contaminants, metals, or pathogens.
The crop can be grown in a normal yeast culture medium, which researchers used during most of their studies, but have also shown that it can grow in tea with sugar. Researchers predict that crops could be customized so people could use them at home to grow water filters or other useful materials.
“Almost anyone can do this in their kitchen or at home,” Tang says. “You don’t have to be an expert. You just need sugar, you need tea to provide the nutrients and you need a piece of Mother Syn-SCOBY. “
The research was funded in part by the U.S. Army Research Office, the MIT Institute for Soldier Nanotechnologies, and the MIT-MISTI MIT-Imperial College London Seed Fund. Tang received support from the MIT J-WAFS Fellowship.