Original source: Materials Today
Inspired by Kombucha tea, a trendy fermented beverage, researchers have developed a new way to generate tough, functional materials using a mixture of bacteria and yeast similar to the kombucha mother used to ferment tea.
With US Army funding, engineers at Massachusetts Institute of Technology (MIT) and Imperial College London in the UK used this mixture, also called a SCOBY (symbiotic culture of bacteria and yeast), to produce cellulose embedded with enzymes. This biomaterial can perform a variety of functions, such as sensing environmental pollutants and self-healing. The team also showed that they could incorporate yeast directly into the cellulose, creating living materials that could be used to purify water for soldiers in the field or to make smart packaging materials that can detect damage.
“This work provides insights into how synthetic biology approaches can harness the design of biotic-abiotic interfaces with biological organization over multiple length scales,” said Dawanne Poree, program manager, Army Research Office (ARO), an element of the US Army Combat Capabilities Development Command (DEVCOM) at the Army Research Laboratory. “This is important to the Army, as this can lead to new materials with potential applications in microbial fuel cells, sense and respond systems, and self-reporting and self-repairing materials.”
The research, reported in a paper in Nature Materials, was funded by ARO and the US Army’s Institute for Soldier Nanotechnologies (ISN) at MIT. The US Army established the ISN in 2002 as an interdisciplinary research center devoted to dramatically improving the protection, survivability and mission capabilities of soldier and soldier-supporting platforms and systems.
“We foresee a future where diverse materials could be grown at home or in local production facilities, using biology rather than resource-intensive centralized manufacturing,” said Timothy Lu, an MIT associate professor of electrical engineering and computer science and of biological engineering.
The researchers produced cellulose embedded with enzymes, creating living materials that could be used to purify water for soldiers in the field or to make smart packaging materials that can detect damage. These fermentation factories, which usually contain one species of bacteria and one or more yeast species, can produce ethanol, cellulose and acetic acid, which is what gives kombucha tea its distinctive flavor.
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 this yeast with a type of bacteria called Komagataeibacter rhaeticus that their collaborators at Imperial College London had previously isolated from a kombucha mother. This species can produce large quantities of cellulose.
Because the researchers used a laboratory strain of yeast, they could engineer the cells to do any of the things that lab yeast can do, such as producing enzymes that glow in the dark, or sensing pollutants or pathogens in the environment. The yeast can also be programmed to break down pollutants/pathogens after detecting them, which is highly relevant to the US Army for chem/bio defense applications.
“Our community believes that living materials could provide the most effective sensing of chem/bio warfare agents, especially those of unknown genetics and chemistry,” said Jim Burgess, ISN program manager for ARO.
The bacteria in the culture produced large quantities of tough cellulose that served as a scaffold. The researchers designed their system so that they could control whether the yeast themselves, or just the enzymes they produce, are incorporated into the cellulose structure. The material takes only a few days to grow, and if left long enough 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 make in very large quantities,” said Tzu-Chieh Tang, an MIT graduate student and the paper’s lead author.
To demonstrate the potential of their microbe culture, which they call Syn-SCOBY, the researchers created a material incorporating yeast that can sense estradiol, 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.
The researchers are now looking into using the Syn-SCOBY system for biomedical or food applications. For example, engineering the yeast cells to produce antimicrobials or proteins that could benefit human health.