Engineers at MIT and Imperial College London have developed a new way of generating hard, functional materials using a blend of bacteria and yeast similar to “kombucha mother” used to ferment tea.
Using this mixture, also called a SCOBY (symbiotic culture of bacteria and yeast), the researchers were able to produce cellulose embedded with enzymes that can perform a number of functions, such as detecting environmental pollutants. They also showed that they could incorporate yeast directly into the material and create “living materials” that could be used to purify water or to make “smart” packaging materials that could 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 central production,”
Lu and Tom Ellis, Professor of Biotechnology at Imperial College London, are the senior authors of the paper shown today in Natural materials. The paper’s lead authors are MIT graduate student Tzu-Chieh Tang and Cambridge University postdoc Charlie Gilbert.
Division of labor
Several years ago, Lu’s laboratory developed a way to use 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 applications. In the new study, the researchers set out to find a way to use microbes to generate larger amounts of more extensive materials.
They were thinking of creating a microbial population similar to a kombucha mother, which is a mixture of certain types of bacteria and yeast. These fermentation plants, which usually contain a bacterial species and one or more yeast species, produce ethanol, cellulose and acetic acid, giving kombucha tea its characteristic taste.
Most of the wild yeast strains used for fermentation are difficult to genetically modify, so the researchers replaced them with a strain of laboratory yeast called Saccharomyces cerevisiae. They combined the yeast with a type of bacteria 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 strain of yeast, they were able to construct the cells to do some of the things that laboratory yeast can do – for example, produce enzymes that glow in the dark or detect pollutants in the environment. The yeast can also be programmed so that they can break down contaminants after finding them.
Meanwhile, the bacteria in the culture produce large amounts of hard cellulose to act as a scaffold. The researchers designed their system so that they can check whether the yeast itself or just the enzymes they produce are incorporated into the cellulose structure. It only takes a few days to grow the material, and if left alone long enough, it can thicken 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,” says Tang. “It is at least a thousand times more material than 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 registers estradiol, which is sometimes found 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 could be replaced by other strains that detect other contaminants, metals or pathogens.
The culture can be grown in normal yeast culture medium that the researchers used for most of their studies, but they have also shown that it can grow in tea with sugar. The researchers imagine that the cultures can be adapted so that people can use them at home for growing water filters or other useful materials.
“Almost everyone can do this in their kitchen or at home,” says Tang. “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 mom. ”
The research was funded in part by the US Army Research Office, MIT Institute for Soldier Nanotechnologies and MIT-MISTI MIT-Imperial College London Seed Fund. Seaweed was supported by the MIT J-WAFS Fellowship.