Decoding artisanal sourdoughs: The interplay of microorganisms, metabolites, and production parameters
Backslopped sourdoughs represent complex microbial ecosystems traditionally characterised by a stable coexistence of lactic acid bacteria (LAB) and yeasts. This study employed a multiphasic approach—combining sourdough metadata, culture-dependent techniques, amplicon-based metabarcoding and metabolomics—to analyse 109 European sourdoughs (primarily from Belgium) collected via a citizen science initiative. While LAB and yeast diversity largely aligned with previous sourdough analyses, three species previously unknown to the sourdough environment were found: Fructilactobacillus vespulae, Geotrichum pandrosion, and Lachancea thermotolerans. Furthermore, this study provides a large-scale characterisation of acetic acid bacteria (AAB) in sourdough. AAB were detected in up to 80.7 % of the samples, with Acetobacter cerevisiae identified as a core species and 14 AAB species reported in sourdough for the first time. Integrated analysis revealed a complexity in sourdough that cannot be described by a single parameter, despite some trends being present. Metabolite profiling further underscored these complexities and suggested that erythritol production may be more widespread among LAB species than previously reported, specifically correlating with Levl. brevis and Lacp. plantarum. These results emphasize that the sourdough ecosystem remains a reservoir of untapped biodiversity and highlight the necessity of multi-angle microbiological analyses to capture the interplay between artisanal practices and microbial community dynamics.