What can a symbiotic colony of bacteria and yeast (SCOBY) found in kombucha teach us about cooperation?  Our summer grant engaged students in a citizen science project using the popular fermented drink Kombucha. The fermenting process allowed students to explore cooperation at the microbial level, as well as identify key elements of an experimental research design. Kombucha forms a microbial ecosystem where bacteria and yeast cooperate to create a protective barrier (SCOBY) against harsh environmental changes and invading pathogens, while allowing other microbes to remain as members of the ecosystem. Manipulating the environment in which SCOBY develops provides an opportunity to explore cooperation and conflict in a living ecosystem.  


We purchased a few supplies for the project including a commercial SCOBY, some coffee filters, a large box of black tea for brewing and large wide mouth gallon jar.  After three weeks of sitting on my kitchen counter our kombucha was ready for use in our experiment and before you ask ….no, I did not taste it before using it in the experiment.


We used kombucha as our experimental condition and then a separate batch of sweetened tea was brewed and served as our control condition.  We further subdivided our experimental and control conditions into pathogen conditions.  Twenty students were invited to participate and swabbed their dominant hand twice. One swab was placed in the kombucha pathogen condition and the second swab was placed in the control pathogen condition.   After hearing about the experiment, students were asked to complete three questions for extra credit. Students were not awarded extra credit for participating in the study but could earn extra credit by identifying the key elements of the experimental design.

The maintenance phase of the experiment lasted 14 days.

The experiment did not go quite as expected. After 14 days of sitting on my kitchen table, the control condition (picture on the right) had almost no visible bacterial growth but the kombucha condition (picture on the left) had visible bacterial growth.  The kombucha condition had started to form another SCOBY (not planned) and had some bacterial growth.  Definitely not how this is supposed to go.

Students who completed the questions about the experiment did worse than I expected identifying the manipulation and method for control (considered Knowledge questions in Bloom’s taxonomy) but exceptionally well identifying the limitations (considered an evaluation question in Bloom’s taxonomy).

What did we learn from our home brewing experience? Students liked seeing the SCOBY hotel (image at the bottom) and the individual SCOBY floating in the mixture. They were curious about the experiment and growing the kombucha.  This project was also an opportunity for the students to participate in an experiment.  I will be replicating the experiment in Fall 2018 with my PSY132 Psychology and Culture course when we talk about cooperation and social behaviors.  Psi Beta will be replicating and expanding on the study during Psychology Day in November – where we hope to get participants with more pathogens.


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