Bakers Rise Up to Tackle Sourdough Mysteries
Donated sourdough starters helped researchers uncover the factors that influence microbial communities in these living cultures.
Laura is an assistant editor for The Scientist. She earned her PhD in biomedical sciences from Rush University by studying how circadian rhythms and alcohol affect the gut.
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Sourdough bread has a longstanding history with humans. People love sourdough’s tangy flavor, but the microbes within the living starters that create these delicious loaves remain a mystery. To find answers, Rob Dunn, an ecologist and evolutionary biologist at North Carolina State University, launched the citizen science project The Science of Sourdough in 2016. Dunn’s group partnered with other researchers to study how a starter’s geographical location influenced microbial species.
“We did not anticipate how much interest there would be,” recalled Lauren Nichols, who worked in Dunn’s group as a lab manager and is now a data visualization analyst at Duke University. More than 500 people worldwide donated their starters, some spanning decades in age—practically family heirlooms!
They used 16S ribosomal RNA sequencing and identified over 70 yeast species, along with the presence of lactic acid- and acetic acid-producing bacteria.1 To their surprise, they found that most starters contained similar bacteria and yeast species, despite their distinct geographic origins. The findings raised more questions about how starters were made and maintained.
This prompted them to explore factors such as aroma, flour type, time to rise, and height of rise. “We’ve engaged with people around the world making wild sourdough,” said Dunn. Home bakers experimented with different flours (white or whole wheat) and locations (indoor or outdoor), reporting their observations over a couple of weeks. From 40 starters, they found distinct growth phases correlated with early shifts in bacterial diversity, with lactic acid-producing bacteria lowering pH in the first few days.2 The types of flour also influenced the bacterial species present, affecting the height and sourness of the starter.
With thousands of more observations to analyze, Nichols said, “We might see things that we didn’t expect, which could give us clues as to where we might focus our energy on future projects.”
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- Landis EA, et al. Elife. 2021;10:e61644.
- McKenney EA, et al. PeerJ. 2023;11:e16163.
