Table_10_Lactic Acid Bacterium Population Dynamics in Artisan Sourdoughs Over One Year of Daily Propagations Is Mainly Driven by Flour Microbiota and Nutrients.DOCX

This study aimed to: (i) assess at what extent traditional, daily propagated, sourdough can be considered a stable microbial ecosystem; (ii) ascertain the drivers of stability/variability. For this purpose, samples of sourdough, flour and environment were collected over 1 year from three different bakeries located in Altamura, Castellana Grotte, and Matera. Culture-dependent and –independent analyses were carried out on all the samples. In addition, sourdough and flour were subjected to biochemical characterization. In all the sourdoughs sampled at the same bakery, cell density of lactic acid bacteria fluctuated of one-two log cycles. However, 16S metagenetic analysis showed that sourdough bacterial microbiota was remarkably stable, in terms of species. Yet, some differences were found during time at intra-specific level. Indeed, bacterial strains succeeded in a 1-year lapse of time or even in 6-months, such as in the case of strains isolated from Altamura sourdough samples. Residual carbohydrates, lactic acid, ethanol and free amino acids varied in the same sourdough collected at different sampling times. These variations could be attributed to combination of various factors, such as fermentation temperature and strain succession. In addition, concentration of flour nutrients varied over 1 year and, in some cases, in a shorter time lapse. This may have favored certain strains over others. For this reason and also because of its inherent contamination by lactic acid bacteria, we found flour as the major driver of strains succession.

本研究旨在：(i)评估传统日常发酵的酸面包在何种程度上可被视为一个稳定的微生物生态系统；(ii)确认稳定/变异性的驱动因素。为此，从位于阿尔图马、卡斯特尔纳·格雷托和马泰拉的三个不同面包店中，收集了酸面包、面粉和环境的样本，时间跨度为一年。对所有样本进行了依赖和独立于培养的分析。此外，对酸面包和面粉进行了生化特征分析。在相同面包店采集的酸面包样本中，乳酸菌的细胞密度在1到2个对数周期内波动。然而，16S宏基因组分析显示，酸面包的细菌微生物群在物种层面上表现出显著稳定性，尽管在种内水平上存在一些时间上的差异。实际上，某些菌株在一年或甚至在六个月的时间跨度内成功存活，如从阿尔图马酸面包样本中分离出的菌株。残留碳水化合物、乳酸、乙醇和游离氨基酸在同一酸面包的不同采样时间存在变化。这些变化可能归因于多种因素的组合，例如发酵温度和菌株更替。此外，面粉营养物质的浓度在一年内以及在某些情况下在更短的时间跨度内变化，这可能会促进某些菌株相对于其他菌株的生长。因此，鉴于面粉本身容易受到乳酸菌的污染，我们发现面粉是菌株更替的主要驱动因素。