Kombucha Culture

If you haven't tasted kombucha yet, you probably will soon. The sour-sweet, fizzy, fermented tea is becoming ubiquitous in trendy cafes, workplaces, and health food stores across America. Where did it come from, and how did it get so popular? And what in the world is the slimy, beige blob that produces it? From German POWs to Lindsey Lohan to a kombucha zoo at Tufts University, this episode explores the history and science of summer's hottest drink.

Kombucha's origins—like almost everything about the drink—are a combination of myth and mystery. According to Tufts University microbiologist Ben Wolfe, all we know is "it was originally produced in parts of China, as well as what is now Russia." Other countries, including Korea and Tibet, have their own kombucha creation stories. Though the exact date and location in which it was first brewed remains obscure, it seems clear that kombucha arose in the Far East, where tea has been popular for thousands of years.

That doesn't explain how kombucha traveled west. But, by translating a little-known paper published in the Deutscher Apotheker Verlag (a German scientific journal) in 1930, Gastropod managed to trace the arrival of the "Indian tea fungus," as the author called it, to Europe following World War I, when it was brought home by German POWs who had been held in Russia. Still, it wasn't until 1990s Los Angeles that kombucha became a commercial success in the U.S., fueled first by the AIDS epidemic, and later by a growing interest in probiotics and gut health.

Kombucha brewing
Wolfe lab kombucha pet; listener Amy Patterson's SCOBY love hotel; and listener Rachel Khong's July brew.

In the episode, listeners meet The Blob (also known as a SCOBY or mother): a fibrous, slippery mat of yeast and bacteria that ferments sugary tea into kombucha. Gastropod co-hosts Cynthia and Nicky bring segments of their own home-brew blobs to Wolfe's lab, contributing to what may well be the world's largest collection of kombucha cultures. (Wolfe created his kombucha zoo by scouring Etsy for samples from around the United States.) The hosts' cultures go head-to-head, competing under the microscope and under the scientists' noses for the healthiest, most fragrant, and all-round best kombucha. Along the way, Wolfe explores the fascinating microbiology behind each culture's unique flavor and behavior.

Gastropod kombucha analysis
Nicky and Cynthia's blobs under the microscope. Courtesy The Wolfe Lab.

While kombucha fans have long promoted the drink as a cure-all, listeners may be disappointed to learn that there's little science supporting such health claims, though Wolfe does suggest a potential mechanism through which fermented tea might have a positive impact on the gut microbiome. But, even though it likely doesn't hold the secret to eternal life, Wolfe is hoping his kombucha collection will help answer much more fundamental questions about microbial life. Along the way, he may even discover how to engineer the perfect blob.
Cynthia and Ben
Cynthia records Ben pipetting.

Listen in now to discover the bizarre history and fascinating science of kombucha, as well to find out whether Nicky or Cynthia's blob won the Great Gastropod Co-Host Kombucha Smackdown.

Episode Notes

Benjamin Wolfe

You can find our microbiologist-in-residence Ben Wolfe at Tufts University, where he heads the Wolfe Lab, as well as on Twitter @lupolabs.

Listener HEX Ferments' terrifying megablob; listener Rachel Khong's more reasonably sized one.

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For a transcript of the show, please click here. Please note that the transcript is provided as a courtesy and may contain errors.


  1. Absolutely loved this episode. Your podcast is so interesting and informative. As a nutrition graduate student at Tufts university, this podcast is a lot of fun.

  2. Loved this episode! I’m a homebrewer of many things, including kombucha, but I’m also a research scientist and very skeptical about the health claims made about kombucha. I loved the science and history in this episode! Well done, as always.

  3. I used to brew kombucha years ago, and would use half green tea and half (non-caffeinated) rooibos tea, to keep the caffeine content low so my daughter could drink it too. It worked really well and I loved the taste. However, I was never able to get the fiz to happen. I recently went to a kombucha class taught by a local brewer who sells her kombucha locally, and she told us about doing a second ferment after the kombucha is ready. This means that you put the kombucha in bottles and put a raisin or small piece of fruit (or ginger) in it – something that has some sugar content. You close the bottle and leave it to sit at room temperature for 1-2 days and that second ferment causes the fiz. I have yet to try it, but I have a SCOBY from the class and am going to start brewing again, looking forward to seeing how it works this time. Also, she recommended brewing in an oak barrel rather than a glass container. This allows the culture to “settle into” its environment – essentially living and thriving in the wood.

  4. Interested in hearing about the biology of the Kombucha made from the scobys vs just the scoby. Since the buch is what we ingest, I’d like to see what’s in that.

    The biologist left out that the tea provides tannins. I’ve read that the yeast, bacteria and cultures feed off the tannins as well as the sugar. Interested in hearing more about that.

  5. Hi Nicky and Cynthia!! Love, Love, LOVE your podcast! As soon as I saw this week’s topic, I had to listen IMMEDIATELY. I’ve been brewing my own kombucha for over a year and I love the brewing experience and enjoying the taste of my own homebrew cultivation. Experimenting with different flavors of the bottling/second fermentation step is so fun and now I’m about to branch out and begin a new set of experimentation with different teas. I would love to be apart of your microbiologist’s sample pool of Scobys…if that become a thing. I’m a scientist by nature and profession and would love to involve my hobby in this interesting collection.
    Keep up the great work!

  6. Fantastically informative, though the one thing I was still wondering about in the end is the high levels of B vitamins listed on the nutritional facts on my bottle of kombucha. Are those vitamins added by the manufacturer, or do the exist in all kombucha? Are they inherited from the tea base?

  7. So how can I get a starter off of Cynthia’s kombucha blob? I would promise to tell everybody who drank the kombucha about Gastropod 🙂

    • I (Cynthia) am certainly willing to hand off part of the blob – but only if you can pick it up in Somerville, Mass. If you’re nearby and want to meet at a coffee shop for the blob hand-off, let me know! Otherwise, I afraid you’ll have to find something a little closer to home. Thanks for listening and writing in!

  8. Loved the episode on Kombucha, and have a little info to share:
    1) instead of worrying about whether brewing diminishes caffeine, simply make it with decaf tea
    2) if you prefer a gentler variety, try jun, which is a subset of Kombucha that has developed to feed on green tea and honey rather than black tea and sugar (the classic brew). Jun is more delicately flavored, less harsh, yet more effervescent, and brews a bit quicker than classic varieties. Try using jasmine green tea for a marvelous delicate floral taste.
    3) if your brew is too vinegary, simply brew it shorter.
    4) I’m a little concerned about that Scoby library, given that the cultures sound like they are being stored right next to each other. If they have aerobic lids you can get cross contamination. Anecdotally we are told to keep various brews over 4 feet apart. Some people say it’s not necessary…yet I’ve seen water kefir grow a Scoby if it is too close.
    5) were all the samples drunk after the first ferment? Let me introduce you to the delight of second fermentation (2F). After the first ferment, remove the Scoby, and strain (not filter) the Kombucha into smaller, pressure-safe, sealable bottles where you flavor it before sealing and letting brew (without the Scoby) another 12 hours to 7 days). Check the bottles daily to make sure the pressure level isn’t too high. Easy flavor options include juice, hunger, etc.
    6) Kombucha Brewers know that you can intentionally vary the yeast and bacteria balance. To reduce the yeast you wash off the brown strands from the Scoby, and filter the kombucha that is used for the starter of the next batch. This will result in a Kombucha that is less fizzy so you can do a longer 2F. To increase the yeast you do the opposite–retain all brown strands and use the strandy stuff for your starter. This will shift your brew and make it more fizzy.
    7) regarding the concept that Kombucha is unlikely to have true health benefits due to the anaerobic nature of the gut: although the Scoby does need oxygen to brew (thus the reason you use a breathable lid), it does not die in an anaerobic environment. When we get extra scobys, we store them in a sealed ‘hotel’. They cease to grow, yet are still alive. Another possible health benefit is in the enzymes and acids that are in the finished product. None of that is proof of the more outlandish claims, of course, but perhaps an avenue for study

  9. I really loved this podcast. I was told to listen to it by a friend who is a scientist at Rock U. I shared a scoby with her a few months ago so she could begin experimenting with brewing. I have been making kombucha for 5 years now and my mother is still going strong. She has great great great…grandchildren all over the US since over the years she has multiplied prolifically.
    A few things I took away from your podcast:
    1. I started my first ever brew with equal parts black tea, hibiscus and rose hips. I have always wanted to try a more herbal approach to diminish the caffeine a bit. I don’t use decaf as I have been under the impression it is chemically processed to remove the caffeine. I steeped the black tea bag for a few minutes and then removed it while continuing to steep the herbs. My scoby grew really nicely in this batch. I will continue to brew a batch like this for us to drink along with the regular brew. I chose the rose and hibiscus based on the low levels of oils they contain. I have ample mothers in case one gets damaged.
    2. I am really interested in how scobies can change to the environment where they are raised. I am wondering about your scoby lab and wondering how long it will take to have uniformity in all the scobies you have collected from around the world.
    A few things I have learned from my 5 years of brewing:
    1. A second ferment is so delicious! It makes the brew fizzy like soda which my kids love. The best flavor for our family is strawberry ginger. Store bought strawberries are not as good as a pick your own strawberry. The PYO strawberry leaves a beautiful rosé color and tons of flavor. Store bought strawberries (and most other fruit) are bland and colorless. If you don’t have access to fresh picked fruit, try a farmers market.
    2. Give away your little babies to as many people as you can. My scoby was a gift and I love carrying on that tradition. Ask around before purchasing one. I give them away to people locally with a little write up of how I brew.
    3. I feel really bad throwing out scobies (and all live cultures for that matter). I feel they are living beings and I save them and care for them until I get far to many. When I am overwhelmed I compost them so I know they are going to a “good place” and will be feeding my vegetable gardens eventually as dirt.
    4. I’ve tasted kombucha jerky and I am not a fan. I didn’t think our bodies could digest cellulose very easily either. Can you confirm this?

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