# The role of flour type and feeding schedule on the sourdough microbiome

## TL;DR

This study shows how different flours and feeding schedules affect the microbial communities in sourdough starters.

## Contribution

The study demonstrates that flour type influences bacterial composition in sourdough, while yeast remains consistent.

## Key findings

- Kazachstania yeast became the most abundant in all sourdough starters regardless of flour or feeding.
- Whole wheat flour increased the abundance of Companilactobacillus bacteria.
- Bread flour increased the abundance of Levilactobacillus bacteria.

## Abstract

Sourdough starters are fermentations of various grains by bacteria and yeast and are of worldwide economic and cultural importance. Sourdoughs are sometimes spontaneously inoculated, and their resident microbial communities are in part shaped by environmental factors, potentially including flour, water, air, human microbiota, equipment, geography, and temperature. The number of different genera of bacteria and yeast found in sourdoughs is large; however, only a handful of species typically dominate an individual sourdough starter. Understanding how and why certain species form a mature climax community in a particular environment is a key question in microbial ecology. To investigate this question, we used a meta-barcoding approach and tested whether different baking flours (all-purpose, bread, and whole wheat) and frequency of feeding, also known as backslopping, shape the sourdough starter microbial community over the course of one month. We found that the yeast genus Kazachstania rapidly rose in frequency and became the most abundant yeast in all starters, regardless of flour type or feeding schedule. In contrast, flour type did affect the bacterial community. Mature sourdoughs all contained the bacterial genera Companilactobacillus, Levilactobacillus, Lactiplantibacillus, Furfurilactobacillus, and Acetobacter, with Companilactobacillus detected at higher relative abundance in whole wheat flour and Levilactobacillus detected at higher relative abundance in bread flour. We conclude that flour can shape the microbial community of sourdough and has potential implications for functional traits.

How organisms disperse and colonize new environments is central to our understanding of biodiversity. Sourdough, the often spontaneously inoculated fermentation of grains by bacteria and yeast, represents a great system to test and observe how microorganisms come to inhabit a particular niche. In our study, we investigate how environmental parameters such as flour type and feeding frequency influence the microbial community. We find that the common sourdough yeast genus Kazachstania is most abundant in all starters regardless of treatment, but we also find a significant effect of flour type on the lactic acid bacteria composition of the sourdough starters. This work shows how the environment can impact the presence and abundance of particular microorganisms and prompts future studies to test how particular lactic acid bacteria species can specialize on certain resources.