Engineers from MIT and Imperial College London have developed a new way to generate tough, functional materials using a blend of bacteria and yeasts similar to the “kombucha mother” that ferments tea.
Using this mixture, also called SCOBY (symbiotic culture of bacteria and yeasts), the researchers were able to produce cellulose embedded with enzymes that can perform various functions, such as detecting environmental pollutants. They have also shown that they can incorporate yeast directly into the material, creating ‘living material’ that can be used to purify water or to make ‘smart’ packaging material that can detect damage.
“We envision a future where different materials can be grown at home or in local production facilities, using biology rather than resource-intensive centralized manufacturing,” said Timothy Lu, an associate professor at MIT in electrical engineering and computer science and in biological engineering.
Lu and Tom Ellis, a professor of bioengineering at Imperial College London, are the senior authors of the article published today in Natural materials. The lead authors of the paper are TIT student Tzu-Chieh Tang and Cambridge University postdoctoral fellow Charlie Gilbert.
Division of labor
Lu’s laboratory developed a way to use a few years ago E coli to create 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, the researchers tried to find a way to use microbes to generate larger amounts of more substantial materials.
They thought of creating a microbe population similar to a kombucha mother, which is a mixture of certain types of bacteria and yeasts. These fermentation plants, which usually contain one species of bacteria and one or more yeast species, produce ethanol, cellulose and acetic acid, which give kombucha tea its distinctive flavor.
Most of the wild yeast strains used for fermentation are difficult to genetically adapt, and the researchers replaced them with a type of laboratory yeast called Saccharomyces cerevisiae. They combined the yeast with a type of bacteria called Komagataeibacter rhaeticus, who had previously isolated their associates at Imperial College London from a kombucha mother. This species can produce large amounts of cellulose.
Because the researchers used a laboratory strain of yeast, they were able to design the cells to do any of the things that laboratory yeast can do – for example, to produce enzymes that glow in the dark, or to detect pollution in the environment. The yeast can also be programmed to break down pollutants after being detected.
Meanwhile, the bacteria in the culture produce large amounts of sticky cellulose to serve as a scaffold. The researchers designed their system so that they could control whether the yeast itself, or just the enzymes they produce, are incorporated into the cellulose structure. It only takes a few days for the material to grow, and if left alone long enough, it can thicken to take up a space as large as a bath.
“We think it’s a good system that is very cheap and very easy to make in many quantities,” says Tang. ‘It’s at least a thousand times more material than the E coli system. ”
Just add tea
To demonstrate the potential of their microbial culture, which they call ‘Syn-SCOBY’, the researchers created a material containing yeast that detects estradiol, which sometimes occurs as an environmental pollutant. In another version, they used a yeast strain that produces a glowing protein called luciferase when exposed to blue light. These yeasts can be exchanged for other strains that detect other pollutants, metals or pathogens.
The culture can be grown in normal yeast culture medium, which the researchers used for most of their studies, but they also showed that it can grow in tea with sugar. The researchers envision that the cultures can be adapted for humans to use at home for growing water filters or other useful materials.
“Almost anyone can do it in their kitchen or at home,” Tang says. “You do not have to be an expert. You just need sugar, you need tea to provide the nutrients, and you need a piece of Syn-SCOBY mother. ‘
The research was funded in part by the US Army Research Office, the MIT Institute for Soldier Nanotechnologies, and the MIT-MISTI MIT-Imperial College London Seed Fund. Tang was supported by the MIT J-WAFS Fellowship.