Jason A Constantas, Dr. John D Hatle
Dr. John Hatle | College of Arts and Sciences | Department of Biology
Due to its rising popularity many people may now know of kombucha; A fermented tea beverage thought to have originated long ago in the region that is now known as China. Through the same process that this familiar beverage is made, there is also the less familiar production of a polymeric bacterial cellulose pellicle that floats on the surface of the culture. This and other forms of bacterial cellulose are the subject of research for several different applications. Bacterial cellulose has potential for use in medicine, textiles, and as a food additive. The tensile strength of kombucha’s leather-like material grown in different sugar concentrations was measured and statistically analyzed. The groups grown in higher sugar concentrations were found to withstand significantly more force before tearing than those grown in low sugar concentrations. Photographs of the pellicles of each group were also taken and compared at 400x magnification.
Hello, my name is Jason Constantas. I go by Trace and They/them/theirs. The title of my project is Kombucha Leather Durability: Sugar Concentration’s Effect on Bacterial Cellulose. I first became interested in this subject when I started making kombucha almost two years ago. I need to start by introducing some terms that I use so that I won’t lose you immediately when I start throwing them around. When the fermented tea drink kombucha is made there is a cellulose mat byproduct sometimes referred to as the “scoby” that floats to the surface. A better term to call this cellulose mat is the pellicle because “scoby” which stands for symbiotic culture of bacteria and yeast, and is better used to refer to the liquid inoculant that supplies the culture to the broth. I had seen that this unique biomaterial was being used on small scales to make some types of clothing so I tried several different ways of growing it at home with varying results. Sometimes I would change the concentration of sugar or use different plants for brewing the tea to change the broth that the culture grows in. And Through those previous trials I started to think of some research questions. I also found through the existing literature on this subject that some scientists are trying to apply bacterial cellulose for medical purposes, and it may have potential for tissue grafting as a biologically inert scaffold to attach tissues to in surgery or to provide a surface for human cells to adhere to and proliferate on. Which I found extremely interesting. There’s also potential for using this to divert food waste, provide alternative sources for cellulose pulp rather than timber and many other exciting applications.
The purpose of this experiment was to show differences in the resulting pellicles based on the initial concentration of sugar in the solution. I created Three groups and into them went different amounts of sucrose as depicted by figure 1. Group 1 with 24g. group 2 with 224g and group 3 with 324g. Each batch was split into ten replicates. The plan was to allow them to grow for two weeks but that was not long enough as the pellicles had formed slower than I had expected they would, so they were allowed to grow for a total of three weeks. They were allowed to dry. Then using a force transducer to record the results I tore each between two binder clips along their weakest line. The material produced was non-homogenous so there were certain directions in which they would tear more easily. So I consistently tore them so the weakest parts would fail first. The range with which we could measure was only up to 1.9 newtons of force, and two of the group three pellicles exceeded that so they were not counted in the statistics. I was able to show a small difference between the first and second groups, even though there was a big difference in the amount of sugar in each of those groups, but the third group was far stronger than the other two groups. The microscope picture provided shows an interesting pattern of congealed spherical structures which appear to be the cell walls of previously living yeast cells, along with dark striations that are from where the pellicle wrinkled during the drying process since the parts that dried first shrank first, and it didn’t all dry completely evenly. And that creates wrinkles which are visible with the naked eye and under the microscope. That picture is 400x magnification under the microscope but depending on what screen you’re looking at it on you’re getting a different level of magnification since that’s the nature of digital replication of photography but I hope that gives you an idea of what it looks like. I also attached a video so hopefully you’ll be able to see that too.
When the pellicles are being formed it’s actually bacteria that are producing and releasing bacterial cellulose. The yeast has a mutualistic relationship with them since it is such an efficient fermentor. Some of the bacteria involved in this process are the wildly popular Lactobacillus acidophilus and the less readily recognized Gluconacetobacter and Acetorbacter genera. Thank you so much for looking at this project and any other projects you looked at digitally this year and may your quarantine be fruitful and not too cabin fever inducing! If you have questions please leave them so I can respond if they have set up that functional or if not email me! Thank you so much!