Influence of Artisan Bakery- or Laboratory-Propagated Sourdoughs on the Diversity of Lactic Acid Bacterium and Yeast Microbiotas

Abstract

Seven mature type I sourdoughs were comparatively back-slopped (80 days) at artisan bakery and laboratory levels under constant technology parameters. The cell density of presumptive lactic acid bacteria and related biochemical features were not affected by the environment of propagation. On the contrary, the number of yeasts markedly decreased from artisan bakery to laboratory propagation. During late laboratory propagation, denaturing gradient gel electrophoresis (DGGE) showed that the DNA band corresponding to Saccharomyces cerevisiae was no longer detectable in several sourdoughs. Twelve species of lactic acid bacteria were variously identified through a culture-dependent approach. All sourdoughs harbored a certain number of species and strains, which were dominant throughout time and, in several cases, varied depending on the environment of propagation. As shown by statistical permutation analysis, the lactic acid bacterium populations differed among sourdoughs propagated at artisan bakery and laboratory levels. Lactobacillus plantarum, Lactobacillus sakei, and Weissella cibaria dominated in only some sourdoughs back-slopped at artisan bakeries, and Leuconostoc citreum seemed to be more persistent under laboratory conditions. Strains of Lactobacillus sanfranciscensis were indifferently found in some sourdoughs. Together with the other stable species and strains, other lactic acid bacteria temporarily contaminated the sourdoughs and largely differed between artisan bakery and laboratory levels. The environment of propagation has an undoubted influence on the composition of sourdough yeast and lactic acid bacterium microbiotas. Many studies have undoubtedly demonstrated the nutritional, sensory, texture, and shelf-life advantages of using sourdough for the manufacture of baked goods (14). Nowadays, sourdough is largely used for making wheat and rye breads, crackers, pizza, various sweet baked goods, and gluten-free products (2,14,20).Based on the biotechnology protocol, sourdough fermentations are usually classified into three types (types I, II, and III) (48). Type I, or traditional, sourdoughs are characterized by continuous (daily) propagation (back-slopping) of the dough at ambient temperatures (20 to 30°C). Typical and traditional Italian breads are mainly made using sourdoughs belonging to type I (27), and, in most cases, only one back-slopping per day is carried out (26,27). A microbial consortium mainly consisting of obligately and/or facultatively heterofermentative lactobacilli and yeasts usually dominates the mature sourdough (48). For sourdoughs made with various cereals, the stable population of lactic acid bacteria seemed to occur through a three-phase evolution within a few days of back-slopping (45). Nevertheless, the stability of the mature sourdough depends on a number of factors, which include the environmental microbiota (e.g., flour and other ingredients, house microbiota), its metabolic activity (e.g., amylase activity, cofactor regeneration capability, and energy synthesis from various ...

Diversity of the Lactic Acid Bacterium and Yeast Microbiota in the Switch from Firm- to Liquid-Sourdough Fermentation

“…What happens to sourdoughs when switched from firm to liquid fermentation, and could the liquidsourdough fermentation be considered another technology option for making traditional baked goods, keeping the characteristics constant? Although mature and used for at least 2 years, firm sourdoughs confirmed the fluctuations of some biochemical and microbial characteristics during daily propagation (7,23). In spite of this, and though the number of isolates was probably not exhaustive enough to describe all the species and strain diversity, the main traits differentiating firm and liquid sourdoughs emerged from this study, and some responses to the above queries were provided.…”

“…Preliminarily, sourdoughs were propagated daily at the laboratory level for 7 days under the conditions used by artisan bakeries. This stabilized the effect of the laboratory environment on the composition of the sourdough microbiota (23). Table 1 describes the ingredients and technology parameters used for daily backslopping of sourdoughs, which lasted 28 days.…”

Development of a method for the direct fermentation of semolina by selected sourdough lactic acid bacteria

“…However, the real effectiveness of the innovative method depends on the daily propagation of the liquid inoculum by the bread maker. Furthermore, it has to be considered that the production of sourdoughs at laboratory-or bakery-level might influence the composition of the fermenting microbiota (Minervini et al, 2012b). Thus, works are being prepared to apply the system reported in this study at large scale level in industrial bakeries and transfer this new technological approach for sourdough production to the bread makers.…”

Effect of Lineage-Specific Metabolic Traits of Lactobacillus reuteri on Sourdough Microbial Ecology

“…Third, L. sanfranciscensis, the key organism in type I sourdoughs, was isolated only in sourdoughs with a long history-months or years-of continuous back-slopping (3,4,33), but laboratory-scale experiments are typically not conducted on that time scale. Competition experiments with back-slopped sourdoughs are nevertheless a sensitive tool to determine the competitivenesses of different strains or species that are inoculated into the same sourdough (11,12,25,34). This study additionally demonstrates that competition experiments with knockout mutant strains provide a quantitative assessment of the contribution of individual metabolic traits to overall competitiveness.…”

“…Sourdough fermentations in bakeries are controlled to achieve a consistent technological function (e.g., fermentation kinetics, level of acidity, and leavening power), while sourdough fermentations in the laboratory are controlled to achieve consistent fermentation conditions with respect to time and temperature (6,11,12,34). Moreover, flour is the only source of bacterial contamination in laboratory-scale fermentations, ex-…”