The Sourdough Project - Rob Dunn Lab


This would be an interesting project to be a part of &/or follow...


The Sourdough Project
Rob Dunn Lab | Public Science Projects

The best sourdough bread is magical. Each bite contains hundreds of different flavors, many of them not yet named by science much less ordinary language. It is this unnamable diversity of aromas and tastes that combines to allow a slice of sourdough bread, simple bread, to be delightful, rich, invigorating, comforting and filling. The trick, of course, is that there is nothing simple about sourdough bread, nothing at all.

[sourdough-ball] Sourdough bread, like many breads, depends upon microorganisms to rise. But whereas most bread relies on a single organism (baker’s yeast, Saccharomyces cerevisiae), sourdough bread depends on many different microorganisms including yeasts, but also bacteria (lactic acid producing species). These microorganisms live in the “starter” used to make sourdough bread. The starter is composed of the sourdough microorganisms and a small allotment of food on which they survive—typically flour and water. If cared for well, a starter can live, essentially, forever. Some starters are young and begin the moment you add flour to water and wait. Some starters are reported to be thousands of years old, as old as the oldest trees in the world.


Sourdough bread has been baked for more than five thousand years, but even after all of those years of caring for starters, generation after generation, moving from one kitchen to the next, huge mysteries remain. We propose to resolve them here. The first mystery is what determines which microbial species are present in a particular starter. The second is which species make the best starter. The third is the question of whether starters, as they age, go through similar trajectories, predictable stages in their history.

Question 1: Where Do Starter Microbes Come From?

Many bakers and chefs, as well as many scientists, will tell you, with great confidence, where the microorganisms found in starters originally come from (or where they will come from if you make your own starter). This confidence is good news. The bad news is that there is great difference of opinion among individuals as to the answer. Some say the microbes come from the bodies of those making bread. Could the Lactobacillus bacterial species in sourdough starters include some of the same Lactobacillus found on and in the bodies of women? Some say the microbes come from the ingredients, the water or the flour. Others say the microbes come from the air of the kitchen in which the sourdough is being made, or maybe from a passing dog. The truth is we don’t fully know. But we can know.

To answer our first question, we will engage people around the world to make sourdough starter in their homes, using identical ingredients, and then sample the microbes in the resulting starter. We will examine whether they best match the microbes on the person who made the starter, the climate in which the starter was made, the location of the home, or something else. We anticipate studying three thousand starters from countries around the world, hopefully this will include variation sufficient to nail down, once and for all, the origin of the organisms on which our best breads depend.

Question 2: Which Starters are the Best?

The question of the best sourdough starters is, of course, subjective and yet it can nonetheless be judged. We propose to do just that by having internationally recognized chefs and bakers taste and judge breads made from each of many of the sourdough starters from around the world. In addition, we will measure flavor profiles of each resulting bread. The sourdough recipes used will be identical, such that the only thing that differs will be the microbes.

Question 3: What Lives in Ancient Starters?

In addition to considering new starters and the factors that shape them, we will also study ancient starters. We will sample some of the oldest starters in the world to understand how different they really are, whether their microbes tell their stories, and how the flavors of ancient starters relate to newer starters (and why). Do you have an ancient starter that you would like us to study? Let us know. We will also be working with historians to record your story and that of the starter in the process.

These questions are, of course, just the starting point. We have much more we want to do, but this will give you a flavor of what we are fermenting in the lab. This project is a partnership between the Natural History Museum of Denmark, Tufts University and North Carolina State University.

What Can You Do Now?

If you would like to be part of this project, you can sign up here:

No cooking experience required! Be sure to indicate whether or not you have an old sourdough starter you would like to share and something about its history. You can participate even if you don’t have an old starter. If you don’t want to participate, but you would like to stay updated about our results, you can sign up as well. As we get organized and ready for the many samples that will come in, we will send out an email inviting participants to get started, participants, that is, and their microbes.



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VWFeature 2016 November 23

A partial answer:

Appl Environ Microbiol. 2015 Oct;81(19):6736-48. doi: 10.1128/AEM.01852-15. Epub 2015 Jul 17.

Lactic Acid Bacteria in Durum Wheat Flour Are Endophytic Components of the Plant during Its Entire Life Cycle.


So these bacteria are found in the wheat berry.

Different growing methods give different mixes of bacteria & yeasts!

Staff 2017 February 5


Protocol for Submitting Sourdough Samples

The Dunn and Wolfe labs are interested in the diversity of microbes that exists in sourdough starters around the world. If you have a starter and a method for making sourdough that has proven to make a risen loaf, send us a sample of your starter!

Please plan to package and send your sample on the same day. If you can, send your sample on a Monday so that samples arrive before the weekend. We don’t want your sample to sit in a shipping warehouse over the weekend!


More details for submitting your samples can be found here:



Staff 2017 September 24

An update from Rob...


The Stories of Sourdough, the Next Step

Recently, we asked you to share your sourdough starters and stories and you did. You shared them not just from the United States, but also from around the world. More than five hundred starters poured into the first lab in their journey, Ben Wolfe’s lab at Tufts, where they were tended to by graduate student Liz Landis, Kinsey Drake and Shravya Sakunala (the undergrads who did a lot of the processing).


At Tufts, the sourdough starters were curated. Liz opened them. She sniffed them. She unwrapped them. She fell in love with their diversity and she chose a handful, thirty or so, on which she would do more research. From those starters, Liz grew the bacteria and fungi that would grow. Liz will then study this subset of bacteria and fungi in much more detail. They will be her long-term quarry and she will report back about them, episodically, over the next three years.


The sourdough starters then traveled in Raleigh, where they were further curated by Erin McKenney, and then on to the University of Colorado. At Colorado Jessica Henley (in the lab of Noah Fierer) has set about identifying the bacteria and fungi present in each sourdough. The bacteria will be first. Jessica will then share those data with Erin who will carry out the next steps. When Erin gets the data from Jessica they will include the list of bacteria (initially) and fungi (later) identifiable from each starter. This list is likely to be longer than the list of microbes that Liz cultivated from the starters; we suspect (though don’t know) that some of the microbes present in starters are not readily culturable. Maybe not. We’ll know soon.


Once Erin has the data, a cascade of next steps will follow. Those next steps will take years. My suspicion is that in ten years we are still resolving new mysteries from the sourdough starters you have shared, maybe in twenty years. But the first step won’t take so long. The first step is that working with Neil McCoy (a design specialist) and Lauren Nichols will make a map on which you can click on your own sourdough sample number and see, from that sourdough sample, which species were present in it. You will also be able to click on other peoples’ (anonymized) sample numbers and see what is present in those starters as well.


Another next step that is already ongoing is that Erin will be working with her colleagues at the North Carolina Museum of Natural Sciences to begin to use the data from these sourdoughs to develop lesson plans that allow teachers around the world to study sourdough in their classes and, in doing so, to help contribute to new science. If you would like to help with the effort to get this science into the classroom, let us know. None of this work is possible without all of you and, as you can see, without the many many of us too.


That is all for now. More soon. I suspect you are anxious to know (soon) which bacteria were in your starter. I can promise we are more anxious and excited. We are like children who have fallen into a dark cave filled with paintings. We can’t see much yet, but soon there will be light.





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