Lhomme Emilie, Lattanzi Anna, Dousset Xavier, Minervini Fabio, De Angelis Maria, Lacaze Guylaine, Onno Bernard, Gobbetti Marco
LUNAM Université Oniris, Laboratoire de Microbiologie Alimentaire et Industrielle, Nantes Cedex 3, France.
Dipartimento di Scienze del Suolo, della Pianta e degli Alimenti, Università degli Studi di Bari Aldo Moro, Bari, Italy.
Int J Food Microbiol. 2015 Dec 23;215:161-70. doi: 10.1016/j.ijfoodmicro.2015.09.015. Epub 2015 Sep 26.
Sixteen sourdoughs (FS1-FS16) used for the manufacture of traditional French breads were characterized by strongly acid conditions (median value of pH 3.5). The concentration of free amino acids (FAA) was highly variable, due to different proteolytic activity of flour used for back slopping and of dominant microorganisms. Median value of cell density of lactic acid bacteria (LAB) was 9.2 log CFU/g. The ratio between LAB and yeasts ranged from 10,000:1 to 10:1. According to the culture-dependent method and 16S metagenetics, Lactobacillus sanfranciscensis was the dominant species in French sourdoughs. FS5 and FS15, propagated according to protocols including one back slopping step at 14 °C, were the only exceptions. High positive correlations were found between L. sanfranciscensis, temperature of back slopping and FAA. The results of this study highlighted the broad adaptability of L. sanfranciscensis to very acid sourdough. Besides species frequently encountered (e.g., Lactobacillus parabrevis/Lactobacillus hammesii, Lactobacillus plantarum and Leuconostoc mesenteroides), first Lactobacillus xiangfangensis (FS5) and Lactobacillus diolivorans (FS15) were found in sourdough. As determined by RAPD-PCR analyses, the sourdough samples showed a different number of strains, ranging from 5 (FS9, FS11 and FS15) to 12 (FS1 and FS13), meaning a highly variable bacterial diversity. Cluster analysis showed that different sourdoughs, especially when propagated in the same bakery, may harbor similar strains. Except for L. plantarum (FS5) and Ln. mesenteroides (FS3), all the dominant species were detected by both 16S metagenetics and culture-dependent method. Yeast diversity was lower than LAB. Except for FS4 (solely dominated by Kazachstania servazzii), yeast microbiota of French sourdoughs was dominated by Saccharomyces cerevisiae. Strains isolated in this study could be a useful base for developing new basic researches on physiology, metabolism, and intraspecific diversity of L. sanfranciscensis, as well as for standardizing the quality of traditional French breads.
用于制作传统法国面包的16种酸面团（FS1-FS16）的特点是酸性很强（pH中位数为3.5）。由于用于回接的面粉和优势微生物的蛋白水解活性不同，游离氨基酸（FAA）的浓度变化很大。乳酸菌（LAB）的细胞密度中位数为9.2 log CFU/g。LAB与酵母的比例在10000:1至10:1之间。根据基于培养的方法和16S宏基因组学，旧金山乳杆菌是法国酸面团中的优势菌种。FS5和FS15是仅有的例外，它们是按照在14°C下进行一次回接步骤的方案进行扩培的。在旧金山乳杆菌、回接温度和FAA之间发现了高度正相关。本研究结果突出了旧金山乳杆菌对极酸性酸面团的广泛适应性。除了常见的菌种（如副短乳杆菌/哈氏乳杆菌、植物乳杆菌和肠膜明串珠菌）外，首次在酸面团中发现了向氏乳杆菌（FS5）和二醇发酵乳杆菌（FS15）。通过RAPD-PCR分析确定，酸面团样品的菌株数量不同，从5株（FS9、FS11和FS15）到12株（FS1和FS13）不等，这意味着细菌多样性变化很大。聚类分析表明，不同的酸面团，特别是在同一家面包店中扩培的酸面团，可能含有相似的菌株。除了植物乳杆菌（FS5）和肠膜明串珠菌（FS3）外，所有优势菌种均通过16S宏基因组学和基于培养的方法检测到。酵母多样性低于LAB。除了FS4（仅由塞尔瓦齐酵母主导）外，法国酸面团的酵母微生物群以酿酒酵母为主。本研究中分离出的菌株可能是开展关于旧金山乳杆菌生理学、代谢和种内多样性新基础研究以及规范传统法国面包质量的有用基础。
