Kombucha Culture TRANSCRIPT

This is a transcript of the Gastropod episode Kombucha Culture, first released on August 9, 2016. It is provided as a courtesy and may contain errors.

BEN WOLFE: What is the blob? So I tell people it is one of the most disgusting fermented foods. I mean, I’ve seen a lot of gross things in my travels. And it is absolutely disgusting. It’s amazing, the microbiology is really cool, but it’s really gross.

CYNTHIA GRABER: Gross, and yet the blob produces one of the most popular drinks around these days.

NICOLA TWILLEY: That’s right, we’re talking about kombucha, the vinegary fizzy fermented tea that, as of 2016, practically has its own aisle at Whole Foods. I’m Nicola Twilley.

GRABER: And I’m Cynthia Graber, and you’re listening to Gastropod, the podcast that looks at food through the lens of science and history. Today we’ll be staring that disgusting blob straight in the face.

TWILLEY: In fact, it’s a co-host blob smackdown. Cynthia’s blob and my blob go head to head and, not to get all reality TV on you here, but our egos are on the line.

GRABER: My blob is totally going to win.

TWILLEY: Yeah, no. But keep dreaming Cynthia. More to the point, we’ll explore kombucha’s mysterious origins and try to figure out how on earth a drink made by a rubbery, slimy blob of bacteria and fungi got to be so popular in mainstream America.

GRABER: We’ll also head to the lab to learn why that kombucha blob produces not just a fizzy drink but also could provide new insights into the microbial world—our absolutely favorite topic!


GRABER: Even the microbes hidden in our guts.


GRABER: This episode is also supported by the Burroughs Wellcome Fund for our coverage of biomedical research.


TIM: So describe kombucha.

EMMA: It’s kind of like a soda for people who don’t like sweet sodas.

TIM: I was going to say it’s, it’s just like tea. Only cold and fizzy and a little sour.

EMMA: With stuff floating in it.

TIM: With stuff floating in it. So it’s nothing at all like tea.

ZEENAT: I love the taste of kombucha. It’s effervescent, refreshing, definitely not for the faint of heart.

KATE: I think kombucha tastes like slightly fizzy sweet and sour soup from a Chinese place made by hippies. Oh, and I drink it all the time.

EVAN: I think that kombucha tastes like spicy fermented 70s hippie water and I don’t drink it very often.

SONYA: I think the best way to describe kombucha, the taste and the flavor of it, it’s like you took tea and mixed it with some beer and then mixed that with a little bit of apple cider vinegar. So if you haven’t tried kombucha you definitely should.

DINA: On my honor I have never had kombucha it before. OK, here we go. The bubbles. Kind of bitter and bubbly like, tastes faintly of—of like beer.  Yeah it’s not. I mean there is something refreshing about it, that part I got. Like it’s a nice little like fizz on the tongue and it’s you know, but it feels a little bit like drinking salad dressing with a fizz. So, so why do people like this exactly?

LAUREN: Um well I really like to drink the kombucha that I make because I find it super refreshing. Also I guess I do drink it with the hope, although I’ve not done tons of research, but I drink it with the hope that maybe I’m getting some probiotics from it, maybe it’s benefiting my microbiome.

GRABER: So Nicky, I first tried kombucha a few years ago, I don’t even remember, but it was by accident. I stopped by a new friend’s house and she asked me if I wanted some kombucha to drink. I thought it was just another kind of tea, and I love tea, so I was like, sure! She warned me that it was a little weird, which I thought was strange. And then I tried it, and, yes, I was kind of shocked, since I expected tea. I don’t think I really fell in love it though until maybe like three years ago. And then this year I started brewing my own at home.

TWILLEY: I don’t know where I first tried it. I’ve had it at yours, which I like. But for this episode, I took the plunge and got my own blob. I ordered it online, and when it arrived I freaked out.

GRABER: You called me up. It was hysterical—you were like, what in the world am I supposed to do with this disgusting slimy thing?

TWILLEY: I felt like I needed to be in a biohazard suit, like in a pandemic movie. It really does look like an alien life form.

WOLFE: And we should clarify too because we’ve used a lot of different names for the blob. And actually there are a lot of confusing names.  So “the blob” is commonly known as a SCOBY which stands for a symbiotic community of yeast and bacteria or, sorry, of bacteria and yeast. I always get that confused. We also called it a biofilm where the microbes have glued themselves together. It’s also called a mother. It’s also called a mushroom which I don’t like to use at all because that implies it’s just fungus. In the lab what we call it is fermented tea biofilm.

GRABER: We like the name blob. And we’re back in the lab with Ben Wolfe.

WOLFE: And I am a microbiologist at Tufts University. I’m an assistant professor at Tufts as well as the microbiologist in residence for Gastropod.

TWILLEY: You know you’ve made it as a podcast when you have a microbiologist in residence. Especially if it’s Ben, because he’s awesome.

GRABER: Ben has been on the show twice talking about cheese. And at our live show at the Museum of Science, he even did some real-time cheese microscopy. The audience got to see microbes moving around in cheese—as they put the cheese in their mouths.

WOLFE: I love cheese but it is much more complicated than kombucha.

TWILLEY: Cheese has a lot of different bacteria and fungi going on, and a lot of different kinds of microbial communities in all the different styles of cheeses. Like Ben says, cheese is complicated. Not to mention Ben’s cheese experiments were stinkier. Which made him unpopular in the lab. So this past year, he’s started flirting with kombucha, which, like we said, is a fermented tea drink. Now as a Brit, tea is my national beverage, but fermenting it? What is that?

WOLFE: So what you do is you make tea, you add sugar to that tea.

GRABER: And then once that sugary tea cools down, you add the blob.

WOLFE: So what is that slimy blob? It’s largely cellulose.  So the thing that is used by trees and plants to build up biomass,they’re using cellulose, that’s their building block for life.

TWILLEY: But it’s not just a woody mat of cellulose. The blob is alive!

WOLFE: In general we see many different species of yeast and a couple different species of bacteria present.

GRABER: And the yeast and bacteria are living together in this cellulose mat doing different things.

WOLFE: So yeasts use the sugar in order to make alcohol so it’s just like in wine fermentation where you go from the sugars that are in the grapes to alcohol in the wine. In this case you’re providing the sugar.  So you have yeast making the alcohol and that alcohol is converted into acetic acid, which is vinegar, by the bacteria.  So in every kombucha, in order to have a successful kombucha, you know as defined by a sort of history, you would have to have yeast to make the alcohol and bacteria to make the acetic acid.

TWILLEY: So like Ben says, the yeast is making alcohol and fizz. And the bacteria is gainfully employed too. They’re making vinegar, from that alcohol. And…

WOLFE: And what’s cool is that microbe, the bacterium that makes the acetic acid that I talked about earlier, that is producing cellulose. It’s like, I tell people it’s like a microbial Spider Man where inside this culture, the slimy blob, it’s shooting out threads of cellulose in every direction.
Why is it doing that? Well, those bacteria need oxygen in order to do their thing, in order to grow and produce the acetic acid. So you can imagine that if you’re in a big jar and you sink to the bottom there’s a lot less oxygen available at the bottom of the jar than the top. So they make this big what we call biofilm—cells of microbes glued together at the top surface—in order to be able to be close to that oxygen.

GRABER: That’s why the blob always floats to the top of your sweet tea. So the end result is this slightly sweet, slightly vinegary fizzy drink—kombucha, that, yes, has a tiny tiny bit of left-over alcohol that the bacteria might not have entirely converted to vinegar. But really, there’s barely any left.

TWILLEY: The yeast converting sugar to alcohol, that’s what happens when you make wine or beer too. So I get why you need sugar to make kombucha. But what is the tea bringing to the party?

WOLFE: The why tea is a really interesting question. So very recently we’ve thought, what if we just leave the tea out? Let’s just give some sugar water to our kombucha and see what happens. It didn’t make a blob. So the tea will have various vitamins, micronutrients in it, things that microbes need to grow in low concentrations that can stimulate the growth of the microbes.  So I was actually really surprised, I thought we’d get a little bit of growth. We got no growth at all. So the tea is essential in order to have the kombucha grow.

GRABER: The other thing that tea brings is caffeine. If you heard our caffeine episode, you know I love tea, but I’m pretty sensitive to too much caffeine. So I really wanted Ben to tell me—can I freely drink kombucha late in the afternoon? Does the blob somehow convert caffeine and take away its potency?

WOLFE: The caffeine question, I’m actually not, I don’t know if people have measured that very carefully to know for sure what happens to the caffeine.

TWILLEY: Like so many kombucha questions, the answer is basically, who knows? This is a pretty uncharted field for science. Listeners, if any of you know of any studies on the caffeine content of kombucha, give us a shout. Cynthia’s beauty sleep is at stake.

GRABER: Ben is trying to make major inroads into the terra incognita of kombucha science. And he’s started by assembling what might very well be the largest kombucha library in the world.

WOLFE: I went to Etsy.com and searched for kombucha. So I got kombucha cultures from Colorado, I got kombucha cultures from California, Vermont, Tennessee—all over the place. And brought them in the lab.

TWILLEY: Right now, Ben’s blob zoo lives in a Tupperware box. It’s only got 25 different communities in it at the moment, but he’s hoping to expand it into the hundreds. Already, it’s unique.

WOLFE: Ah, I might go ahead and say, yeah, we might be the most diverse kombucha collection in any one place at any point in time. Thank you Etsy, I guess.

GRABER: And while people say ‘kombucha’ as if it’s all one thing, they’re not. Ben showed off his kombucha collection to us.

WOLFE: What’s really surprising when you put all these different kombuchas from all over the world that have been grown or all over the United States that have been grown in the same environment in the lab, they look really, really different.  They look—it’s subtle. It’s a blob. But some blobs are really clear. Some blobs are really thick, some blobs are really stringy. So that—by appearances they’re really different and by smell they’re very different as well. Some of them smell a lot like stone fruits, you get peaches, you get really, really sort of fruity flavors. Some of them smell like dirty Band-Aids, some of them smell like wet leather. I don’t know if dirty Band-Aids is really a smell but, you know, like a Band-Aid essentially. So you get a lot of different smells and that’s partly coming from the different yeasts that are present. It’s impressive just how different these slimy blobs can be.

TWILLEY: The fact that these blobs are all slightly different communities of yeast and bacteria—that makes the final drink they produce taste different. Which brings us to a very personal topic. Our own mothers. Or I guess, to be consistent, our blobs.

GRABER: We each brought a small segment of our personal blobs in their brewing liquid into the lab. We’re donating our kombucha cultures to science, but really? We want to know whose is best.

TWILLEY: So first the sniff test. My blob went first.

WOLFE: Oh, hello, hello.

GRABER: It’s pretty strong. Smells good. Smells like kombucha.

WOLFE: It does. It smells like a classic kombucha.

TWILLEY: This is my first ever batch, you know.

WOLFE: Oh really? Congratulations.

TWILLEY: I was feeling pretty good at this point. And then Ben sniffed Cynthia’s blob.

WOLFE: Oh. Different.

TWILLEY: Oh yours is less—mine’s more vinegary.

WOLFE: Yeah, yeah.

GRABER: I think I won the sniff test. But that’s not the end of the kombucha competition.

WOLFE: What we’re going to do is look at them in the microscope to just sort of get a feel for what they look like and we may already see some differences there. And then what we’re going to do is incorporate them into our culture collection and see how fast they grow, to see if they grow differently. We’ll sequence the yeast and the bacteria that are there so we’ll learn a lot about what’s inside your kombucha.

TWILLEY: Is there prizes for everyone or does only one of us win?

WOLFE: It’s unclear what winning is in kombucha, so…

GRABER: I can tell you my winning would be to know that I am not poisoning me and Tim.

WOLFE: Oh, I think we’ll find that out for sure. Yeah.

TWILLEY: So Ben sterilized the scalpels and prepped the Petri dishes, and set up the slides for the microscope.

WOLFE: So this is Cynthia’s blob. Let’s get a chunk of…

GRABER: Cut it this morning. I’m not sure how perfectly sterile everything was.

TWILLEY: I should have fished it out for you guys but I wanted to touch it as little as possible to be totally honest. It looks like raw chicken breast.

WOLFE: That’s been sitting on the sidewalk for a while.

GRABER: And then he took a look at Nicky’s blob.

WOLFE: OK, I’m going to go in there … oh my.

GRABER: Oh, yours gets a lot goopier than mine does. Mine doesn’t look like that.

WOLFE: It looks like a manta ray, look at it like…

GRABER: Mine just forms the layers. I don’t get all that like weird goop.

WOLFE: So we’re really fascinated by…

GRABER: Nicky’s totally grossed out.

WOLFE: Do you need a barf bag? We have a biohazardous waste bin over there that you can just go vomit in. We’re really interested in the strings. So one thing that’s really common is there’s like the strings that hang down. And when Liz in the past has looked at the strings it turns out they’re yeasts.  They make these long—so yeast are normally circular cells but sometimes they can make these elongated cells. And we’re trying to figure out why the yeasts are doing that, why are they making the strings? And a hypothesis we have, it’s not been tested at all, is that it might be an escape. They may be actually trying to get out of the kombucha environment, which is kind of stressful for them, for yeast. The acetic acid, the vinegar isn’t the most pleasant thing to be bathed in. And so we think it could potentially be a stress response. But we haven’t tested that yet but…

TWILLEY: It’s going to climb out of the side of my jar in the night.

WOLFE: But yeah there it is. Oh it’s beautiful.

TWILLEY: It’s not beautiful. Even a mother could not say that. Hah.

TWILLEY: So my blob smells worse but it has these exciting gross string things — so this might be a dead-heat. Right?

GRABER: You just keep thinking that.

WOLFE: Are you ready with a microscope?

LIZ LANDIS: We’re incubating right now. It takes about 15 minutes.

TWILLEY: That’s Liz Landis, she’s a grad student in Ben’s lab and she’s been leading their kombucha research.

GRABER: So while Ben and Liz are incubating our kombucha blobs so that we can peer at them under a microscope, let’s take a moment to reflect on some of the mysteries of this bizarre drink. Like, where does it come from?

WOLFE: What we do know is that it was originally produced in parts of China as well as in Russia. It’s very, very popular there and it has been historically. Many different families would have them in their kitchens and drink them. There’s various names for them in different cultures. But how, you know, someone learned to originally make kombucha and that it was a good thing, I’m not really sure. I mean, it makes sense that it would happen pretty spontaneously. If someone was making tea and they added sugar to it, if you leave that out, there are yeasts and there are bacteria in the air that could colonize that, if you’re in the right place. But when did that happen? When did people start purposely cultivating it? What was the original kombucha in terms of which yeast or which bacteria? We don’t know. Yeah.

TWILLEY: There are lots of legends about Chinese emperors and Tibetan monks and Korean doctors, most of which have no evidence behind them at all. The trail leads all over the place in the Far East—the Asian steppes of Russia, China, Japan, Korea—basically, everywhere that people drank lots of tea.

GRABER: There aren’t many good resources about kombucha science and kombucha history. For instance, it’s hard to say when kombucha left Asia and made its way to Europe and then North America. Ben handed us a copy of one scientific paper in German from 1930s. Luckily, one of us can read German.

TWILLEY: Kind of. But enough to figure out that Mr. Valentin, the author of the paper, had done some serious detective work on the subject. He wrote to the editors of 29 different pharmaceutical journals all over Europe to ask if they’d heard of this weird drink, which he called Indian tea fungus. He got 77 letters back and from that information, he deduced that the blob—and the brewing technique—had spread to Europe from Russia originally, via German prisoners of war. So after the first World War, those German prisoners brought blobs home with them, and kombucha spread outward from there. In 1930, kombucha was most common in Central Europe but it hadn’t yet reached the edges—no one he wrote to in Scandinavia or in England had heard of it.

GRABER: That’s almost a century ago. It took about 80 years until I first tried it, it certainly wasn’t hugely popular in the US until recently. So here’s the next mystery—when did it catch on here?

NORMAN BAKER: You know these mushrooms are alive and they have an intelligence. It’s like plants, they know that they are here to help people.

TWILLEY: That’s Norman Baker of Laurel Farms, in Los Angeles. And that’s an archive clip from the AP, from the first wave of the American kombucha craze, back in the early 1990s.

GRABER: Norman’s coming from the type of hippie communities that started popping up in the 1970s. And you could find kombucha in those communities—people shared their blobs. It was super niche. Nobody else really knew about it.

TWILLEY: But then, in the 1990s, a couple of things happened. Norman and his partner Betsy Pryor were given a blob by her meditation instructor, and they started selling baby blobs mail order as a cure-all.

BETSY PRYOR: Because it is making a difference in people’s health, it is profound. And we would like to help heal the planet, that’s what we’d like.

BAKER: Well I’m very different. I’m actually a recovering quadriplegic. I’m one of the few quadriplegics in the world that has ever come back. Right five fingers on, still very slow. But the bottom line is that my hair was receding, and all of a sudden my hair started to fill in. Instead of coloring my hair every 28 days—and I owned a group of hair salons in Los Angeles—now I haven’t colored my hair in over two months.

TWILLEY: That’s Betsy and Norman again. Apparently kombucha stops grey hair, restores movement to quadriplegics and heals the planet.

GRABER: Of course it does.

TWILLEY: Amazing.

GRABER: The thing is, kombucha has always had this sort of healthy halo around it. Even in that German paper from 1930, the author writes that it’s suspected to have health benefits, but that it’s not proven. Paul Stamets—he’s this really famous fungus guy in Washington State—he wrote in the mid 1990s a whole list of what kombucha is supposed to be able to do: cure cancer, cure rheumatism, improve vision, improve sex, cure diabetes, get rid of white hair, grow black hair, cure herpes, cure insomnia, and, yes, even this, reverse the symptoms of AIDS.

TWILLEY: And that last thing—that’s actually what’s behind kombucha’s first big boom. Betsy and Norman start shipping their blobs mail order with a sticker on them saying “Expect a Miracle.” And they were super popular in the Los Angeles AIDS community and that’s how it spread across the country.

GRABER: You have to remember that at the time there was no effective therapy for AIDS. Of course kombucha didn’t cure it. But people were grasping at whatever straws they could. In an LA Times article from 1995, doctors estimated that about a fifth of their AIDS patients were regularly drinking kombucha.

TWILLEY: In that same article, Norman Baker, bless his heart, said that kombucha has an intelligence well above the level of a dolphin.

GRABER: I don’t even know how to respond to that. But at the time The New York Times estimated that three million Americans were growing kombucha at home. Newsweek called it “Snapple for the crystal set.”

TWILLEY: But then two things happened. In 1995, scientists began rolling out an effective new cocktail of drugs to treat AIDS patients. And then right at the end of that year, the Centers for Disease Control issued a warning, saying that kombucha might have been responsible for the deaths of two women in Iowa. The connection was never proven and the women were already pretty sick—that’s why they were chugging so much kombucha in the first place. But the warning made national news. And so the kombucha bubble burst.

GRABER: But not forever. Not all of those blobs were tossed in the trash. In fact one blob lived on in Los Angeles at the house of GT Dave.

TWILLEY: His real name is George Thomas, and he is very muscular and shiny looking. And GT Dave is the person who really made kombucha mainstream. His parents introduced him to it—they scored their blob from a friend who had gone into juicing instead, and the friend’s blob came from a Buddhist monk. Which is about the most LA thing I’ve ever heard.

GT DAVE: Kombucha came into the household that I grew up in when I was barely a teenager. My parents, who are very spiritual and very holistic, started making it and drinking it. I at the time thought it was very weird, but it wasn’t until my mother was diagnosed with breast cancer and kombucha played a strong role in helping her overcome the breast cancer and remain strong throughout her treatments, is when I became encouraged to give kombucha another chance. And I started to make it and drink it and I quickly fell in love with it and noticed how it improved my life.

GRABER: There are obviously some problems with that story, but, in any case, GT Dave saw a business opportunity. He dropped out of school and started bottling kombucha at age 16. This is in mid 1990s, and he’s selling kombucha to the same health-food, crystal-type communities that already loved the drink. But by the mid 2000s, he took kombucha mainstream: to Whole Foods.

TWILLEY: There’s a couple of reasons analysts think kombucha caught on again in the mid 2000s. At the time, the Atkins diet was really popular, and that was pushing people away from sugary sodas, and maybe into the arms of kombucha. And then the functional beverage category as a whole was blowing up—you get Coke acquiring Vitamin water and all the energy drinks and so on. It was a new millennium and people wanted to drink something that promised to do something for them. Kombucha fit that bill too.

GRABER: And here’s where Lindsay Lohan comes in. That’s a sentence that has literally never been uttered before on Gastropod and likely never will again. Remember how we told you that the yeast turn the sugar into alcohol, but there’s basically none left in your glass? Well, Lindsay had a court-issued alcohol-monitoring bracelet on. And she was a kombucha drinker. And so it was rumored that perhaps it was the kombucha that set off her monitor. Maybe.

TWILLEY: Either way, stores starting pulling kombucha from the shelves. CNN reported on the issue from a bottling plant in Colorado.

CNN: Federal regulators claim their kombucha has too much alcohol content after some samples tested above .5 % alcohol by volume, about 1/8 the alcohol in a light beer. The Alcohol and Tobacco Tax and Trade Bureau, or the TTB, has sent letters warning of possible fines, suggesting new labeling and threatening to move the drink from grocery store shelves into liquor stores.

GRABER: In the end, it turns out that the problem stemmed from just a few samples, and kombucha is still not considered an alcoholic drink. But this whole alcohol kerfuffle might have actually done kombucha more good than harm.

TWILLEY: Right, and then came the probiotic craze. All of a sudden in 2012, 2013, Americans started worry about the microbes that lived in their guts, really for the first time. And kombucha sales rocketed in response, growing by up to 40 percent year on year. And now it’s to the point where your workplace is not trendy if you do not have kombucha on tap.

GRABER: But that brings us back to something we discussed a little earlier—all those crazy health claims. People are drinking kombucha now largely because they think it’s good for them. But, really, is it?


TWILLEY: OK, I think we’ve left you all on a cliffhanger for long enough. People have claimed kombucha is healthy for millennia, people have said it will cure everything from diarrhea to cancer. So, is that true? Is kombucha the miracle elixir of life?

WOLFE: People have done various studies often using human cells in a dish, or a mouse or rat model. And they have shown that various components of kombucha, various chemical components of kombucha, can do things like inhibit the growth of certain bad microbes or, you know, reduce inflammation. There are not, as far as I’m aware, any really really thorough, good studies in humans showing that those effects are actually very robust when you’re eating a whole bunch of other things and not just drinking kombucha all day.

GRABER: So, basically, there is no scientific evidence in humans for all of those health claims.

WOLFE: That said there there is a lot of potential for the probiotic components of kombucha to potentially do something—again it’s all potential. So you can think about it in two ways. There are a bunch of microbes living in this tea, it’s a fermented tea. So you can have direct or indirect indirect effects of those microbes. The direct effects of those microbes could be that they’re actually living in your gut. You drink that kombucha, it’s full of all these living cultures, and they’re hanging out inside of you and doing something. Now that to me is a little bit problematic for a couple reasons. First of all, no one’s actually demonstrated that after you consume kombucha, that those microbes are viable or are doing anything. That scientifically has never been demonstrated before.

TWILLEY: And Ben thinks it’s actually unlikely. Because the microbes in kombucha need oxygen, that’s why the blob forms on the top. And your gut doesn’t have a whole lot of oxygen. So no one has done this experiment to show that the live cultures from kombucha actually do set up shop in your gut but Ben’s not betting on it. But there is another way that kombucha could have health benefits, again, not proven, but maybe more likely.

WOLFE: There also could be indirect effects. So these microbes that are growing in the tea can make metabolites, they can make things that could be beneficial. Or the dead cells of these microbes as they’re passing through could be food for the microbes that live in your gut. That has also not been demonstrated but it is a potential probiotic or prebiotic effect of kombucha. So I think there’s a lot of potential. But at the same time I think we have to figure out a lot more about the system before we can make a lot of the claims that are out there.

GRABER: So, the jury’s out. Scientists do seem to believe that microbe-rich fermented foods like miso and yogurt and sauerkraut are all generally good for us. Kombucha is one of those. But there’s no science that backs up any specific health claim.

TWILLEY: And what about those deaths and the CDC warning. Can the reverse be true? Can kombucha kill you?

GRABER: I was actually worried about that. Like, what if I was slowly poisoning Tim with this homebrew?

WOLFE: So in terms of you know pathogenic microbes and kombucha, it’s not necessarily a very happy place for many pathogens. So as long as you’re reaching the right acidity then you won’t necessarily get the growth of those.

GRABER: Ben’s not saying that everything has to be super sterile. Just clean the jar, put a cloth or a paper towel over top of the kombucha as it brews, you should be fine.

WOLFE: You could get molds in there and molds can make what are called mycotoxins which can make people sick. But you need to have a lot of mold in order for that to be a problem. And you’ll know—you’ll see the fuzzy layer.

TWILLEY: Don’t drink your kombucha if your blob turns green. That seems like common sense to me. But, fingers crossed, both of ours are happy health blobs. And mine went under the microscope first.

TWILLEY: Don’t let me down. Oh. Well there’s stuff going on!  There is little—there are rounder things, more like rice-like things.

LANDIS: So a little rice-like things or the bacteria and the yeast are kind of floating on the outside.

GRABER: And is it actually moving?

TWILLEY: Oh, it’s moving!

WOLFE: So acetic acid bacteria can be motile. Some of them do have motility.

TWILLEY: I got a mover

GRABER: You got a swimmer.

TWILLEY: I love it.

GRABER: Do we need to do a comparison?

TWILLEY: Yeah, we need to look at Cynthia’s, I think, otherwise she’ll start feeling jealous.

GRABER: I am, I’m feeling a little jealous here.

ALL: Oh. Oh there we go. Oh.

TWILLEY: I don’t see as much movement. I’m not seeing the swimmers.

GRABER: Oh, there they are, see?

BEN: Competitive microscopy, this is… It looks like Cynthia’s Cynthia SCOBY has a bit more yeast in it.

GRABER: Which is what you thought because it was pretty cloudy.

BEN: Exactly. So that could just be the age. It may not have anything to do with, you know, its overall integrity, it just might be when we harvested it. So we’ll get back to you on that. But we’ll know, as we grow them, we can look at cell density, we can look at the species diversity, how thick and big it is. And we can really figure out which one is better.

GRABER: Now you’re playing into our competition here.

GRABER: But Ben’s interest in kombucha is not actually about whether my blob is better than Nicky’s.

WOLFE: I think some of the things that we’re doing, where we’re trying to understand just how microbial communities work, you know, we’re not really studying this for the sake of the food. We’re really studying it for the pure basic science perspective.

TWILLEY: And he studies a variety of microbial ecosystems—sauerkraut, sourdough, of course cheese—but kombucha has a real advantage. It’s super simple.

WOLFE: There’s only a few parts there, there’s only a few species of microbes present, which allows you to go in and really understand the complete system. As opposed to something like soil or the human environment where there’s many different species of microbes living together and it’s much harder to pull them apart and put them back together again.

TWILLEY: Like for example, we might want to be able to engineer a healthy human gut. And we would have no real idea where to start right now. But if Ben can use something simpler like kombucha to tease out how a microbial community works, then maybe, he thinks, he can arrive at microbe design principles.

WOLFE: Can we come up with some basic rules that allow us to go to a new system and say if you consider X, Y, and Z, you should have a good shot of designing the microbial community that you want, given you know a certain set of parameters. And that’s really hard, no one’s even really done that in a food system, a simple food system, like this yet.

GRABER: One of the questions is, can you swap out one microbe you might want to get rid of for another one that you might actually want to have in a system? Kombucha is a great model for studying how that might work. There are only a few different types of yeasts and bacteria in any given kombucha blob.

WOLFE: And we don’t have a good explanation right now as to why some yeasts are present in one kombucha and why some are in another. What we do know is that there is some interchangeability in the system—that you can take one yeast from one kombucha and stick it into another one, experimentally in the lab, and it’ll do the same thing as the other yeast would do.

TWILLEY: If Ben can figure out what is making these yeast able to swap in and out in kombucha, maybe that can help us understand out how to swap microbes in and out in general.

GRABER: The next big question they want to tackle is really cool—they haven’t started it yet but they’ll be looking for volunteers soon. They want to understand how the microbial community in the kombucha blobs change over time.

WOLFE: So this is something we’re really excited about. So one of the main questions that we’re trying to understand in the kombucha system is how microbes evolve in a community. And so what we hypothesize is happening inside of these systems is if we all started off with the same culture and then gave it to let’s say 20 different people, and some of those people use a little bit more sugar or some of those people use black tea instead of green tea, some people lived in a warmer environment versus a colder environment, those microbes can slowly change, mutations can pop up. Maybe those are beneficial, maybe the interactions between the yeast and the bacterium can change over time.

TWILLEY: Ben and Liz are planning a big experiment where they give volunteers an identical blob and track what happens to it over time. They have to figure out some more of the kombucha basics first, but stay tuned—they’ll be looking for volunteers.

GRABER: I’m in. But here’s what you’ve been all been waiting to find out.

TWILLEY: Or at least we have. Sleepless nights, I’m telling you.

GRABER: Who won the great kombucha brew-off?

WOLFE: Hello.

TWILLEY: Hey Ben, how are you?

WOLFE: Good, how are you doing?

TWILLEY: Pretty good. Yeah, I’m a little bit nervous actually, but, you know.

WOLFE: Don’t be, don’t be.

GRABER: I’m kind of excited to hear about—you know, also a little nervous, but looking forward to hearing about how our little pets are doing.

WOLFE: Yeah! So what’s really exciting to me, there are clear differences between each of your kombuchas. So there’s clear differences in terms of what microbes are present, there’s clear differences in the amounts of the microbes that are present. Cynthia’s biofilm is a very sort of delicate, kind of undulating, not as rigid, and very flexible, and a little heterogeneous,you know, there’s a lot of variation across the surface. Whereas Nicky’s was this really thick rigid disk that was just—you can kind of see in the picture, I wish you could hold it in your hand after it’s been growing in the lab but it’s just like this really thick mass of microbes. So that was really striking to see.

GRABER: I was wondering if this has anything to do with personalities

TWILLEY: I mean, I am reading a lot into it.

WOLFE: This is so funny because I was thinking the same thing but I didn’t want to bring it up.

TWILLEY: So, it turns out my blob is rigid. And it’s more vinegary than Cynthia’s. My blob had lots of acetic acid bacteria that produce vinegar and not very much yeast.

WOLFE: So, I had everyone in the lab come over and we were doing a sort of a a sniff test of your two different kombuchas living in the Petri dishes, in the very controlled environment, in the lab. What’s really cool is that Cynthia’s kombucha has this very sort of stone fruit, very fruity, sort of almost floral aromatic to it. Whereas Nicky’s, it’s like sticking your nose in malt vinegar.

TWILLEY: Oooh. Crushed.

WOLFE: When we did the DNA sequencing this sort of keeps—the theme keeps going. So Cynthia had a very specific yeast. It’s called a Zygosaccharomyces. And when we smell that yeast growing in the lab, it’s very floral, it has this sort of—again it smells almost like a really fresh peach. And then Cynthia also had another yeast called Brettanyomyces, which is the same thing—you probably heard about it in wine and beer, it’s called Brett. And then Nicky only had the Brett. So she was missing that sort of floral, fruity yeast that is contributing to that aroma that we have in Cynthia’s. So it’s really cool, the microbiology actually can explain a lot about the differences between your kombuchas. And so everyone’s a winner. You know, Cynthia gets the fruity floral yeast, and then Nicky has more of a bacterial SCOBY, and that’s, you know, not necessarily a bad thing at all.

TWILLEY: Aw, Ben. He’s trying to sugarcoat it but really, I hear what he’s saying. Cynthia won. To be fair, I do actually prefer your kombucha, Cynthia

GRABER: We should also tell the listeners that even before we heard the results, you’d already killed off your blob.

TWILLEY: It just wasn’t me. I’m not vinegary and rigid, I swear!

GRABER: Hey, if you’re ever want to try again, I’m happy to hand off some of my blob. It gets really big, really quickly, and I regularly have to prune it back.

TWILLEY: That’s my take-home from this episode: if you’re going to get into this whole homebrew kombucha thing, get your blob from someone whose kombucha you actually like.

GRABER: And, if you buy one and you don’t like it, maybe give it another try with a different brand or a flavored variety. It might just be that you don’t like that kombucha.

TWILLEY: That said, Ben did mention something that kind of almost made me regret throwing my blob out.

WOLFE: So what we’re finding in the lab is that if you change the amount of sugar or if you actually use different tea to brew the kombucha, the culture behaves very differently and actually can smell and taste differently. So for example when you use black tea versus green tea the culture looks totally different and behaves totally different.

TWILLEY: Maybe my blob just didn’t appreciate my super strong British tea bags.

GRABER: For me, the big relief, apart from finding out that I’m not poisoning myself, is that kombucha really isn’t that high maintenance. You don’t have to feed the blob regularly, you just have to leave it in some of the brewing liquid. Go away on vacation, don’t make it for a while, whatever. The blob will survive and be fine and then you can make more later.

TWILLEY: But in true reality TV style, Ben saved the big reveal for the end.

WOLFE: This may be a bit of a shocker. Tell all. So I think that kombucha is the cilantro of fermented foods. Because I know you guys love cilantro.

GRABER: No, I hate it. She loves cilantro.

WOLFE: I enjoy tasting it when I do. I think it’s an interesting beverage. I do not drink it regularly because I am just not really into it. It doesn’t really appeal to me. I think the microbiology is amazing and I love that people are excited about it but it’s just not something I drink regularly. So the truth is out.

TWILLEY: Oh. My. God.

GRABER: So disappointed.

GRABER: I do actually love it—I don’t like drinks that are too sweet, so I love the kind of clean, refreshing flavor. Of mine, that is, not yours, Nicky’s.

TWILLEY: And I think it’s OK. Yours is, anyway. Mine was grim. But Cynthia, I feel like normally we do a better job of answering our own questions—like where is kombucha from and is it really the health elixir people claim. Did we fail?

GRABER: I don’t think so. I think it’s pretty safe to say that kombuchas from the Far East. Also safe to say that it’s not bad for you, and, you know, it’s a fermented food, and in general it seems like fermented foods are good for you. Unfortunately, even though people have been drinking it for thousands of years, there isn’t that much good science on it yet. But Ben has a parting word of wisdom for kombucha drinkers.

WOLFE: I will say that drinking something that makes you happy is a wonderful thing. Eating something that makes you happy, as long as it’s not dangerous, it’s a wonderful thing, so drink on.

TWILLEY: And I will raise a glass of anything but my kombucha to that.



GRABER: Thanks again to the Burroughs Wellcome Fund—they support our coverage of biomedical research. And a huge thanks this episode to our our microbiologist in residence, the one and only Ben Wolfe. We’ve got links to his lab’s website online in our episode notes, so you can keep up with all the cool research going on there. We’ve got photos of our kombucha blobs under the microscope and they are amazing. We’ve also got photos of some of your kombucha blobs—you guys sent in some bizarre shots. Gastropod.com.

TWILLEY: Thanks also to Liz Landis, who is a grad student in Ben’s lab and is leading the kombucha research. She dug out historical papers, prepared our blobs for their close-up under the microscope, and even helped out during our live show too.

GRABER: Thanks too to everyone who sent in sound files of your attempts to describe kombucha to aliens.  As always, you can support us with a positive iTunes review, by suggesting us to friends and family, or, if you are able, by donating to us on Patreon or through our website. We have special rewards available for supporters who give $5 an episode or $9 a month, too—check them out on our website gastropod.com or at Patreon.

TWILLEY: And thank you! For listening and for all your support. We’re back in two weeks with a special collaboration all about salt.