The Bac[tea]rial Beauty of Kombucha

Lets begin like this…

A guy walks into a café. Guy sits down and Hypothetical Waiter approaches to greet him. Hypothetical Waiter says, “Hey there, welcome! What can I get for you”?

Guy says, “Hi! I’d love a big cup of tea please. Oh, and can I get that extra yeasty and with a generous helping of bacterial growth”?

This is not a bizarre scenario that I’ve fabricated in my head. Ever heard of kombucha? No, it’s not a spell recited at Hogwarts; it’s a fermented beverage increasing in popularity in the Western world and making its way into grocery stores and homes all over. If you had an especially enjoyable, but potentially self-destructive, St. Patrick’s Day you’ll definitely want to hear me out on this one.

Kombucha “SCOBY”.  Photo taken from Brokelyn, as originally seen in Craigslist ad.

Kombucha “SCOBY”.  Photo taken from Brokelyn, as originally seen in Craigslist ad.

What is that?

As with many of the presently popular foods and beverages, kombucha tea may be perceived as a hip, new elixir but it’s actually been around for a very long time. Even if you’ve seen it on the shelves, you may not totally understand what it is or where it came from so I hope to reveal some of that information here. With supposed origins in China, kombucha is at its essence, tea.  But the story doesn’t end there. Traditional preparation begins with brewing black tea and sweetening it with a sucrose, or sugar. Mmm. At this point, a “mother” culture of bacteria and fungi, which home brewers lovingly refer to as a “SCOBY” (symbiotic culture of bacteria and yeast), is added to the surface of the fresh tea and left to hang out and get cozy at room temperature for about eight to twelve days during which some whacky microbiology and biochemistry happens.

Chemical structure of cellulose, where “n” indicates that this molecule can for a long chain of multiple cellulose molecules.  Photo from Wikipedia [bacterial cellulose].

Chemical structure of cellulose, where “n” indicates that this molecule can for a long chain of multiple cellulose molecules.  Photo from Wikipedia [bacterial cellulose].

Bacteria producing cellulose.  Photo from Virginia Tech University News (www.vtnews.vt.edu).

Bacteria producing cellulose.  Photo from Virginia Tech University News (www.vtnews.vt.edu).

The fungal yeast thrives off of the sugars in the tea and produce carbon dioxide and ethanol through the process of fermentation (channel your inner beer brewing knowledge here). Like a true friend, the ethanol produced by the yeasts is shared with the various strains of bacteria that surround it, which are able to use it to produce things like acetic, gluconic, and lactic acids as well as naturally antimicrobial compounds.  How does that slimy SCOBY form, you ask? Some bacteria present are able to use sugars (glucose from the yeasts and sucrose from the tea) to make something called bacterial cellulose. It’s an organic compound (made of carbon, hydrogen and oxygen) that is able to form long chains by linking itself together with other identical cellulose molecules. These chains are eventually able to create a fibrous and structural network that rests on the surface of the liquid tea. The cellulose acts as a comfy home to all the bacteria and yeast colonies that are snuggled inside, so dense that it takes on an almost solid (mildly revolting), gel-like appearance. It is this physical characteristic that often earns brewing kombucha the nickname “tea fungus”.

Right: Example of kombucha presently being brewed at home. Left: Collection of bacterial cellulose pellicles produced by previous cultures. These may be used to start new, future batches of kombucha. Photo courtesy of beautiful home-brewer, Kelly Fitzpatrick.

Right: Example of kombucha presently being brewed at home. Left: Collection of bacterial cellulose pellicles produced by previous cultures. These may be used to start new, future batches of kombucha. Photo courtesy of beautiful home-brewer, Kelly Fitzpatrick.

If you’re repulsed but simultaneously intrigued, keep reading.

If you have a thought process similar to mine, you may have already developed concern about the risks involved with culturing kombucha at home on the kitchen counter. I’m no germaphobe, but working in a research lab has made me aware that you often may not know what exactly is growing in that petri dish. It may seem a bit paradoxical if I were to say that kombucha tea actually has antimicrobial properties since it’s covered (quite literally) in all sorts of colonies. The cool thing is, it seems to prevent growth of foreign microbes because the colonies that are a part of the culturing process are already utilizing all of the available space and nutrients present. This is on top of the fact that the extreme conditions that develop as a result of fermentation (super low pH/high acidity, rapidly decreasing oxygen availability) are most likely not well-tolerated by nasty intruding organisms while the ‘good’ bacteria in kombucha are adapted to handle them. It’s like built in protection! [Shout out to the lovely Kelly Fitzpatrick, Assistant General Manager of the historical Chicago Diner, for sharing some of her experience and images of her very own SCOBYs!]  

Still wondering why someone would actually drink this stuff? Yeah, me too.

From what I can tell, kombucha has a plethora of supposed benefits associated with drinking it.  As a trained skeptic, it was this very fact that inspired me to begin looking for credible research studies on its biological qualities that may be related to health. While no human studies have been published with results supporting strong health benefits, my searches led me to a number of experiments in the past decade that identified some interesting biological properties. Here’s a snippet of a few neat-o things I spent some time reading about.

Example of bacterial growth and various sized zones of inhibition. Larger regions of clearance represent a greater inhibition of bacteria growth resulting from whatever may be present in the circular disc at the center.  Photo taken from nature.com/blogs.

Example of bacterial growth and various sized zones of inhibition. Larger regions of clearance represent a greater inhibition of bacteria growth resulting from whatever may be present in the circular disc at the center.  Photo taken from nature.com/blogs.

Antibacterial.

I’ve already described that kombucha cultures seem to outcompete foreign invaders, but what is more interesting is that the resulting fermented tea itself (filtered and rid of its bacteria and fungi) also possesses the ability to inhibit foreign bacterial and fungal growth. Scientists produced their own controlled batch of kombucha tea broth, put it in the center of petri dishes, and then spread each dish with one type of bacteria. After letting the bacteria grow and spread over the dish, clear regions around the kombucha center developed, called “zones of inhibition”. The larger the zone, the more the tea prevented growth of that particular bacteria strain. Kombucha has been seen to exert strong antimicrobial effects against Staphylococcus epidermis, Micrococcus luteus, Listeria monocytogenes, Pseudomonas aeruginosa, Salmonella choleraesius, and everyone’s favorite, E. coli.

Commercially available kombucha.  Photo taken by Mattina Alonge.

Commercially available kombucha.  Photo taken by Mattina Alonge.

Antioxidant-rich.

In addition to the other acids I’ve already mentioned, glucouronic acid (GlcUA) is another predominant compound produced by kombucha bacteria and released into the tea. It’s a well-established detoxifier and acts as a harvester of toxic chemicals and compounds, fancifully called xenobiotics, biochemically changing them so that they are more easily excreted from the body. Antioxidants are important in protecting our internal biochemistry against oxidative stress.  Oxidative stress is bad news for mitochondria, which are inside cells making a huge amount of ATP (cellular energy source). Maybe my love of biochemistry is being reflected here, but mitochondria are the life force of the animal cell! If you screw with the mitochondria, you screw with a lot of other really important processes that can ultimately limit our built-in internal defenses and even cause cell suicide. Regular, ol’ black tea is chock full of phenols, which are natural antioxidant molecules. The culturing and fermentation process increases the number of phenolic molecules tremendously thereby increasing antioxidant potential. Perhaps it’s possible that regular consumption of kombucha may be helpful in prevention of metabolic disorders caused by oxidative stress, such as psoriasis, asthma, gout, migraines and potentially neurodegenerative diseases like Alzheimer’s; but it’s safe to say that a lot of experiments need to be designed and executed before one can make any biologically-based conclusions.

Hepatoprotective. (Protects your liver!)

Okay, hopefully you are fully recovered from what may have been a weekend truly unkind to your liver. If not, here are some reasons to consider giving kombucha a taste. One of the predominant strains of bacteria present in kombucha cultures, named Gluconacetobacter sp. A4, was found to produce a very high amount of a potent detoxifying compound called D-Saccharic acid 1,4-lactone (DSL for short). DSL is normally present at pretty low levels in the body and doesn’t naturally reach amounts that would exert its beneficial effects.  It’s thought that drinking kombucha could help supplement levels to a degree to which the liver-protecting benefits would be seen, keeping it happy and healthy. Another study using mouse liver cells combined kombucha with tertiary-butyl-hydroperoxide (TBHP), a chemical known to cause oxidative stress in the liver. Oxidative stress, if maintained, will eventually cause them to commit suicide from the inside out.  By pairing TBHP treatment with kombucha tea, critical steps toward cell death that would have occurred were prevented! To bring this back to St. Pattie’s Day, tons of oxidants (things that cause oxidative stress) are seen in alcohol-associated liver diseases. Maybe next time you’re at the bar you’ll consider chasing those shots of Jameson with something a little kinder to your hard-working and (let’s be honest) oddly adorable mitochondria.

Happy mitochondrion.  Photo credit: http://h2ohauck.deviantart.com.

Happy mitochondrion.  Photo credit: http://h2ohauck.deviantart.com.

For now, my story ends like this…

The Hypothetical Waiter pauses, smiles ever so slightly, and replies, “You got it. One tall glass of kombucha coming right up”.

Mattina M. Alonge received a M.S. in Biology from DePaul University under supervision of Dr. Jason Bystriansky where she explored expression of Na+/K+-ATPase isoforms in rainbow trout muscle during swimming challenges. She is currently working at University of Chicago Dept. of Medicine in a translational research lab while also finding time to practice yoga, put her figure skates on, look forward to summer flying trapeze classes, and read stacks of books supported by her membership in a hipster book club.