Taxonomic Structure and Stability of the Bacterial Community in Belgian Sourdough Ecosystems as Assessed by Culture and Population Fingerprinting

Abstract

A total of 39 traditional sourdoughs were sampled at 11 bakeries located throughout Belgium which were visited twice with a 1-year interval. The taxonomic structure and stability of the bacterial communities occurring in these traditional sourdoughs were assessed using both culture-dependent and cultureindependent methods. A total of 1,194 potential lactic acid bacterium (LAB) isolates were tentatively grouped and identified by repetitive element sequence-based PCR, followed by sequence-based identification using 16S rRNA and pheS genes from a selection of genotypically unique LAB isolates. In parallel, all samples were analyzed by denaturing gradient gel electrophoresis (DGGE) of V3-16S rRNA gene amplicons. In addition, extensive metabolite target analysis of more than 100 different compounds was performed. Both culturing and DGGE analysis showed that the species Lactobacillus sanfranciscensis, Lactobacillus paralimentarius, Lactobacillus plantarum, and Lactobacillus pontis dominated the LAB population of Belgian type I sourdoughs. In addition, DGGE band sequence analysis demonstrated the presence of Acetobacter sp. and a member of the Erwinia/Enterobacter/Pantoea group in some samples. Overall, the culture-dependent and culture-independent approaches each exhibited intrinsic limitations in assessing bacterial LAB diversity in Belgian sourdoughs. Irrespective of the LAB biodiversity, a large majority of the sugar and amino acid metabolites were detected in all sourdough samples. Principal component-based analysis of biodiversity and metabolic data revealed only little variation among the two samples of the sourdoughs produced at the same bakery. The rare cases of instability observed could generally be linked with variations in technological parameters or differences in detection capacity between culture-dependent and culture-independent approaches. Within a sampling interval of 1 year, this study reinforces previous observations that the bakery environment rather than the type or batch of flour largely determines the development of a stable LAB population in sourdoughs.Traditional sourdoughs comprise a complex microbial association of lactic acid bacteria (LAB) and yeasts and are thought to improve sensory, texture, and health-promoting properties of many bakery products (15). During sourdough fermentation, the prevailing LAB produce acids (mainly lactic acid and acetic acid) that lower the pH of the sourdough medium. In addition, these organisms are responsible for the production of ethanol, aroma compounds, bacteriocins, exopolysaccharides, and several enzymes (17). Sourdough LAB may originate with natural contaminants in the flour or with a starter culture which contains one or more LAB strains (6). Sourdough can be cultivated in bakeries or obtained from commercial suppliers. In Belgium, many artisan bakeries still use spontaneously fermented sourdoughs, which are kept metabolically active through the addition of flour and water at regular intervals (backslopping). During this process of continuous propaga...

Diversity and dynamics of bacterial populations during spontaneous sorghum fermentations used to produce ting, a South African food

“…In addition, biases at the level of DNA extraction and PCR specificity and efficiency [9,14,17] could also have played a role. The inability of PCR-DGGE to detect all the bacterial species associated with fermented sorghum was also observed for sourdough [49,71] and whey cultures of water buffalo mozzarella [16]. PCR-DGGE results are also strongly influenced by the intraspecific heterogeneous nature of the 16S rRNA gene region targeted [18,74], which might be the case for putative Pantoea and Enterobacter spp.…”

Lactic Acid Bacterium and Yeast Microbiotas of 19 Sourdoughs Used for Traditional/Typical Italian Breads: Interactions between Ingredients and Microbial Species Diversity

“…Principal component analysis (PCA) using a correlation matrix was carried out to visualize the effects of ingredients and technology parameters on the sourdough microbiotas and the effects of the microbiotas on the biochemical features of the sourdoughs. For each sourdough, a microbial community profile was composed which reflected the qualitative (number of species) and quantitative (number of strains per species) diversity of LAB and yeasts (36). The chemical composition of the flours (concentrations of maltose, glucose, fructose, and total and individual FAA) or other ingredients and microbial community (cell density of LAB and yeasts, number of species, number of strains, and percentages of obligately homofermentative and obligately and facultatively heterofermentative LAB) data were used as variables for PCA analyses.…”

“…The chemical composition of the flours (concentrations of maltose, glucose, fructose, and total and individual FAA) or other ingredients and microbial community (cell density of LAB and yeasts, number of species, number of strains, and percentages of obligately homofermentative and obligately and facultatively heterofermentative LAB) data were used as variables for PCA analyses. In addition, microbial community data were also analyzed together with the biochemical characteristics (pH, organic acids, quotient of fermentation, ethanol, and FAA) of sourdoughs (36). All data were standardized before PCA analysis using the statistical software Statistica for Windows.…”

Codominance of Lactobacillus plantarum and obligate heterofermentative lactic acid bacteria during sourdough fermentation

“…namely L. rossiae, is being frequently isolated at high numbers from sourdoughs produced in Italy (Valmorri et al, 2006;Di Cagno et al, 2007) and it has been also detected in Belgian sourdoughs (Scheirlinck et al, 2007(Scheirlinck et al, , 2008. The majority of LAB screened and selected to act as starters in sourdough production belong to OHe species (Minervini et al, 2012;Settanni et al, 2013).…”

“…Gobbetti (1998) reported on the L. sanfranciscensis/L. plantarum association in Italian wheat sourdough, and Scheirlinck et al (2008Scheirlinck et al ( , 2009 found that the species L. paralimentarius, L. plantarum, L. sanfranciscensis, Lactobacillus pontis and Lactobacillus spicheri were dominant in type I sourdoughs produced in a Belgian bakery. Recently, L. plantarum has been detected at high cell densities, even higher than those of the OHe LAB species, also in Asian sourdoughs (Luangsakul et al, 2009;Zhang et al, 2011), highlighting the relevance of this species to produce sourdoughs throughout the world.…”