Bacterial Fizzy Drink that can be good for you? Kombucha - ferment it yourself at home!
Updated: Aug 24, 2022
Good morning little microbes! Welcome to another class here in the wonderful kitchen of the Society of Symbionts! During the Giants' Great Covid Quarantine many turned to the comfort of baking foods like bread, which includes fermentation - a microbial process, to ease stress. But as the summer heat settles in, hours of baking can uncomfortably raise the temperature of their homes, you see, the Giants are also sensitive to their environments! Fret not my microbial bakers, there are other fermented foods that microbes can assist the Giants to create and refresh in the dog days of summer! Let's ferment to make an amazing ancient drink that's fizzy and delicious, and may even be beneficial to the gut microbiome - Kombucha!
Three quick fun facts about Kombucha!
Fact 1: Personal testimonies (not science!) claim this magical elixir has the ability to cure many ailments: from improving your liver, immune system, gastric function to increasing vitality, and curing AIDS and cancer. While we can't prove all that - it at least has to be healthier than most other sodas!
Fact 2: Kombucha has been around for thousands of years with origins likely stemming from China as far back as 220 B.C.
Fact 3: It's also known as: Cainii grib, Fungus japonicus, Cembuya orientalist, Tschambucco, Volga spring, Mo-Gu, Champignon de longue vie, Teekwass, Kwassan, Kargasok tea, Cainii kvass, Japonski Grib, Heldenpilz or Jsa Kvaska.
Fun to drink, Fun to say: Kombucha!
So my little microbes, Kombucha is actually a fermented tea, created through an intricate series of interactions between both bacteria and yeasts. Our first step is to dissolve sugar into boiling water and then steeping tea leaves (either green, black or blue [oolong] ) for a short time.
So where do the microbes come in to play?
Good question Mia, microbes are added once the tea is at room temperature; you see, if it is too hot and the poor microbes will die before they get to eat all of that sugar and cause fermentation!
Yeah, but how do they get in there?
So Anna, unlike viruses like you who are transmitted via droplets or on surfaces from an infected host to an uninfected host, when making Kombucha, microbes are inoculated (fancy science word for added) into the tea purposefully in two ways:
First, the brewer adds a SCOBY (a gross looking blob of microbes)
Second, add a small portion of the last fermented tea batch (or white vinegar in pinch). This is known as back-slopping. It is a common practice in many microbially fermented foods such as sourdough, fermented meats, cereals, yogurt and kefir.
A cloth or other material that allows for air flow is then placed on top of the container and the mixture is allowed to ferment (a chemical change that happens to a substance - in this case, our tea - as a result of microbes eating sugar) at room temperature for 8-14 days. The cloth allows for aerobic (oxygen) conditions while excluding pesky insects and other intruders. Anaerobic (without oxygen) can drastically change the microbial profile and undrinkable tea.
So.....what's a SCOBY?
A SCOBY is a zoogloeal mass of microbes. SCOBY stands for Symbiotic Culture Of Bacteria and Yeast. Because Kombucha has been home-brewed for thousands of years, the microbial diversity is quite expansive. It can be rather diverse or simplistic depending on where, when, and who created it.
As with most cooking, microbes play a key role! Bacteria that produce acetic acid are common in all brews, are also used in cocoa bean fermentation and wine, and are rod-shaped (1-4um long). The most common genera found in Kombucha are Gluconobacter, Gluconacetobacter, and Komagataeibacter.
As the Giant's discover more about how microbes can help them via their gut microbiome, there has been a surge of interest in this ancient drink, leading the scientific community to study it. Go consumer demand! The increasing demand has, in today's market, increased variety where we can now find everything from fruity to alcoholic kombucha products.
Kombucha may have some other uses as well outside of being a magical elixir. Kalaiappan and colleagues manipulated the SCOBY to create activated carbon. This combined with sulfur, graphene oxide, polyacrylonitrile, at just the right conditions produces a composite cathode. Which may have used in future lithium-sulfur batteries. But that's a little beyond the scope of this post.
Arikan and colleagues looked at the microbial profile of two Turkish Kombuchas to see if the profile changed over time. To do so, they followed a very strict recipe in preparing the kombucha and sampled on days 3, 10, and 15 of the fermentation. They extracted DNA for both full genome analysis and also for amplicon (a piece of DNA) sequencing. Amplicon sequencing is a cheaper method allowing scientists to identify what the microbe is. Whole-genome analysis is more expensive but can allude to function or what the microbe is capable of.
One drawback to DNA analysis is it does not tell you if the microbe is alive or active, only if it is/was present and the functions it could perform. There are also several ways of extracting DNA. Each way will extract differently and will have biases towards certain groups of microbes. Moral of the story? Science is a balancing act between the best method and the resources available.
Anyways, methods aside, Arikan found Komagataeibacter as the dominant bacteria, comprising over 90% of the bacterial profile! Komagataeibacter, like many acetic acid bacteria, uses glucose to produce gluconic acid and ethanol to produce acetic acid. Komagataeibacter may be inhibiting the growth of pathogens, which cannot survive in acidic conditions. The acidic environment may also contribute to Kombucha's antimicrobial benefits.
Yeasts are the other microbial element in Kombucha. They are spherical and much bigger than bacteria (~8um; 2-8x bigger!). They are known for their ability to produce ethanol (alcohol) and carbon dioxide (bubbles!). In kombucha, the typical yeasts found are Saccharomyces, Zygosachharomyces, Dekker/Brettanomyces, and Pichia. In our Turkish Kombucha study, Zygosachharomyces was almost 100% of the yeast community. This yeast can convert sugars (added at the beginning of the process) to produce glucose and ethanol (used by the acetic acid bacteria).
So the yeast and bacteria are best friends sitting in this paradise created for them, chatting it up, exchanging goods, and creating their ideal environment. They are lowering the Ph, producing vitamins, and antimicrobials so no one can disturb the little bromance they got going. They are living their best life! That is until, on one hot summer day, a Giant crack open a bottle and imbibes their whole world.
So it goes.
Benefits of Kombucha
Scientifically, kombucha may provide mild benefits to the consumer. It is thought the low Ph probably has detoxifying and antimicrobial features. Kombucha may also be a beneficial antioxidant, and the caffeine in the tea can be energizing and may even stimulate your immune system. It may be beneficial to managing or preventing some diseases but certainly doesn't replace medical care.
Despite it being full of microbes that don’t harm you, Kombucha is likely not a great source of probiotics. Acetic acid bacteria are not known to provide benefits and most described to date as being probiotic belong to lactic acid bacteria. Although these microbes are found in some Kombucha, they are not ubiquitous and may not survive in storage.
So what happens then? You drink the microbes, their metabolites, the acid. Will you live forever? Have you been cured of all ailments? Of course not! But did you enjoy a nice, low-calorie refreshing beverage that might have some health benefits? You sure did! So get your ‘buch’ on and happy brewing!
Would you like to hear from a kombucha brewer? Check our interview with Christopher Drozd
Do you brew your own kombucha? What is your favorite flavor of kombucha? Tell us in a comment below!