Engineers at MIT and Imperial College London have developed a new way to generate hard and functional materials using a mixture of bacteria and yeast similar to the “mother kombucha” used to ferment tea.
Using this mixture, also called SCOBY (symbiotic culture of bacteria and yeast), the researchers were able to produce cellulose embedded with enzymes that can perform a variety of functions, such as detecting environmental pollutants. They also showed that they can incorporate yeast directly into the material, creating “living materials” that could be used to purify water or make “smart” packaging materials that can detect damage.
“We anticipate a future in which various materials could be grown at home or in local production facilities, using biology rather than resource-intensive centralized production,” said Timothy Lu, an associate professor of electrical and computer engineering and biological engineering.
Lu and Tom Ellis, professor of bioengineering at Imperial College London, are the lead authors of the paper, which appears today in Materials for nature. The main authors of the paper are Tzu-Chieh Tang, a graduate of MIT, and Charlie Gilbert, a postdoc.
Division of labour
A few years ago, Lu’s lab developed a way to use it And there 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, the 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 aroma.
Most wild yeast strains used for fermentation are difficult to genetically modify, so researchers have replaced them with a laboratory yeast strain called Saccharomyces cerevisiae. They combined yeast with a type of bacterium called Komagataeibacter rhaeticus, which their 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 any of the things that laboratory yeast can do – for example, by producing enzymes that glow in the dark or by detecting environmental pollutants. The yeast can also be programmed so that it can decompose pollutants after their detection.
Meanwhile, bacteria in the culture produce large amounts of hard cellulose to serve as a scaffold. Researchers have designed their system so that they can control whether yeast, or just the enzymes they produce, are incorporated into the structure of cellulose. It only takes a few days to grow the material and, if left long enough, it can thicken to take up as much space as a tub.
“We think this is a good system, very cheap and very easy to make in very large quantities,” says Tang. “It is at least a thousand times more material than And there 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 smells of estradiol, which is sometimes found as a pollutant for the environment. 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 pollutants, metals or pathogens.
The culture can be grown in a normal yeast culture environment, which the researchers used for most of their studies, but also showed that it can grow in sugar tea. Researchers predict that crops could be customized so that people can use them at home to grow water filters or other useful materials.
“Almost anyone can do this in their kitchen or at home,” says Tang. “You don’t have to be an expert. All you need is 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 U.S. Army Research Bureau, 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.