Yeast species composition differs between artisan bakery and spontaneous laboratory sourdoughs

Abstract

Sourdough fermentations are characterized by the combined activity of lactic acid bacteria and yeasts. An investigation of the microbial composition of 21 artisan sourdoughs from 11 different Belgian bakeries yielded 127 yeast isolates. Also, 12 spontaneous 10-day laboratory sourdough fermentations with daily backslopping were performed with rye, wheat, and spelt flour, resulting in the isolation of 217 yeast colonies. The isolates were grouped according to PCR-fingerprints obtained with the primer M13. Representative isolates of each M13 fingerprint group were identified using the D1/D2 region of the large subunit rRNA gene, internal transcribed spacer sequences, and partial actin gene sequences, leading to the detection of six species. The dominant species in the bakery sourdoughs were Saccharomyces cerevisiae and Wickerhamomyces anomalus (formerly Pichia anomala), while the dominant species in the laboratory sourdough fermentations were W. anomalus and Candida glabrata. The presence of S. cerevisiae in the bakery sourdoughs might be due to contamination of the bakery environment with commercial bakers yeast, while the yeasts in the laboratory sourdoughs, which were carried out under aseptic conditions with flour as the only nonsterile component, could only have come from the flour used.

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

“…These results were in agreement with previous studies on sourdoughs from the center and south of Italy (31,39). The dominance of a few strains of S. cerevisiae can be related to contamination by baker's yeast (45). The dominance of C. humilis has been shown in Pagnotta del Dittaino PDO sourdough (21).…”

“…K. barnettii and K. exigua were isolated only from Pane nero di Castelvetrano sourdough. K. exigua has previously been isolated from a number of sourdoughs (16), whereas the presence of K. barnettii in wheat sourdoughs is reported only in one previous paper (45).…”

Influence of Temperature and Backslopping Time on the Microbiota of a Type I Propagated Laboratory Wheat Sourdough Fermentation

“…Besides the L. sanfranciscensis-C. humilis association, associations of Saccharomyces cerevisiae and L. plantarum, Candida spp. and L. brevis, and Kazachstania barnettii and L. sanfranciscensis have been reported too (4,27,55). Furthermore, sourdough continues to be a source of unexplored LAB species diversity, as exemplified by the continuous reporting of new LAB species (11).…”

“…This demonstrates the large microbial diversity present in sourdough. Moreover, since these species are mostly isolated in exploratory studies of a limited number of fermentations, it remains a challenge to know what the exact reasons are why one species should be dominant over another or present in one sourdough environment and not in another.In previous studies, it has been shown that type I sourdough fermentations carried out in the laboratory with flour as the sole nonsterile ingredient harbor a different species diversity than artisan sourdoughs prepared in a bakery, with respect to both LAB and yeast species (42,43,49,55,57,58). Laboratory sourdoughs based on wheat, rye, or spelt, daily backslopped for…”

“…In previous studies, it has been shown that type I sourdough fermentations carried out in the laboratory with flour as the sole nonsterile ingredient harbor a different species diversity than artisan sourdoughs prepared in a bakery, with respect to both LAB and yeast species (42,43,49,55,57,58). Laboratory sourdoughs based on wheat, rye, or spelt, daily backslopped for…”