Living materials inspired by kombucha tea
Engineers at MIT and Imperial College London developed a new way to generate tough, functional materials, using a mixture of bacteria and yeast similar to the way kombucha tea is made.
Kombucha is fermented tea, which is made with a mixture of certain types of bacteria and yeast, called SCOBY (symbiotic culture of bacteria and yeast). These bacteria produce ethanol, cellulose and acetic acid to give the tea its flavour.
With a mixture similar to this, the researchers produce cellulose embedded with enzymes that can perform a variety of functions, such as sensing environmental pollutants. Another function was by incorporating yeast directly onto the living material, it was possible to purify water or make ‘smart’ packaging that can detect damage.
Most 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, isolated from a kombucha mother. This species can produce large quantities of cellulose.
Because they used a laboratory strain of yeast, the researchers could engineer cells to do anything lab yeast can do, like producing enzymes that glow in the dark, or sensing pollutants in the environment. The yeast can also be programmed so that they can break down pollutants after detecting them.
It takes only a few days to grow the material, which the researchers dubbed Syn-SCOBY. The method is easy enough that anyone could do it at home if they have a piece of Syn-SCOBY mother.
The researchers used it to make a material that senses oestradiol, which is sometimes found as an environmental pollutant. In another version, they used a strain of yeast that produces a glowing protein called luciferase when exposed to blue light. These yeasts could be swapped out for other strains that detect other pollutants, metals, or pathogens.
Images: Chenfu Hsing / Tzu-Chieh (Zijay) Tang / MIT