Engineers at MIT and Imperial College London have developed a new way to create tight, active products using a mixture of bacteria and yeast similar to the “mother kombucha” used to make tea.
Using this combination, also known as SCOBY (symbiotic culture of bacteria and yeast), the researchers were able to inject cellulose with an enzyme capable of performing a number of functions, such as environmental pollutants. They also showed that they could introduce yeast directly into the material, creating “living materials” that could be used to purify water or to find “smart” packaging that could detect damage.
“We look forward to a future where diverse products can be grown at home or in local production facilities, using biology rather than resource-intensive centralized manufacturing,” says Timothy Lu, professor associated MIT in electrical engineering and computer science 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 Natural Materials. The paper’s lead authors are MIT graduate student Tzu-Chieh Tang and Cambridge University postdoc Charlie Gilbert.
Department of labor
Several years ago, Lu’s laboratory developed a method of its use E. coli to generate biofuels 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 tried to find a way to use microbes to generate larger amounts of more substantial materials.
They were thinking of creating a microbe population similar to the mother of kombucha, which is a mixture of specific types of bacteria and yeast. These fermentation factories, which usually contain one or more species of bacteria and one or more species of yeast, produce ethanol, cellulose, and acetic acid, which give kombucha tea a unique flavor.
Most of the wild-type rays used for fermentation are difficult to genetically modify, so the researchers replaced a laboratory yeast called Saccharomyces cerevisiae. They combined the yeast with a type of bacteria called Komagataeibacter rhaeticus, whose colleagues at Imperial College London had previously separated from kombucha’s mother. This species can make a lot of cellulose.
Because the researchers used laboratory rays of yeast, they were able to engineer the cells to do any of the things that lab yeast can do – for example, make enzymes that shining in the dark, or feeling polluted in the environment. The yeast can also be programmed so that they can break down contaminants after detection.
At the same time, the bacteria in the culture produce large amounts of tight cellulose as a scaffold. The researchers designed their system so that they can 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 long enough, it can take up as much space as a bathtub.
“We think this is a good system that is very cheap and very easy to make in large quantities,” Tang says. “It’s at least a thousand times more stuff than E.coli system. ”
Just add tea
To demonstrate the potential of their microbial culture, known as “Syn-SCOBY,” the researchers created a material containing estradiol-sensitive yeast, which is sometimes found as an environmental pollutant. In another version, they used a yeast strain that releases a glorious protein called luciferase when exposed to blue light. These gaps could be adjusted for other sequences that detect pollutants, metals or other pathogens.
The culture can be grown in the medium of conventional yeast culture, which the researchers used for most of their studies, but they have also shown that it can be grown in tea with sugar. The researchers speculate that the cultures could be adapted for human use at home to grow water filters or other useful materials.
“Almost everyone can do this in their kitchen or at home,” Tang says. “You don’t have to be an expert. You only 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 U.S. 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.