Microbial consortia involved in fermented spelt sourdoughs: dynamics and characterization of yeasts and lactic acid bacteria.

This study aims to describe the native microbiota of fermented spelt, taking into consideration both lactic acid bacteria (LAB) and yeasts, for which little data are available. Five samples of commercial spelt flour were subjected to spontaneous fermentation to obtain a type I sourdough. A total of 186 LAB and 174 yeast isolates were selected at different refreshment steps and subjected to further analyses. Within LAB, coccal isolates constituted 78·5% of the total LAB, with the dominance of Pediococcus pentosaceus. Although documented before as a component, this is the first report of a spelt sourdough fermentation dominated by this homofermentative LAB, characterized by a high acidification rate, ability to utilize a wide range of carbon sources and to grow in high osmolarity conditions. Yeast communities resulted in four dominant species, Saccharomyces cerevisiae, Wickerhamomyces anomalus, Pichia fermentans and Clavispora lusitaniae. This study highlights for the first time the biodiversity and dynamics of yeast communities involved in sourdough fermentation of spelt. Compared to commercial baker's yeast, autochthonous W. anomalus, P. fermentans and S. cerevisiae isolates show a good performance, and their use could be an advantage for their acquired adaptation to the environment, providing stability to the fermentation process. SIGNIFICANCE AND IMPACT OF THE STUDY: Nowadays, there is a renewed interest in products based on spelt. This 'ancient grain' is a highly nutritional grain; however, its use is limited to bread-making processes, which are not standardized. The low baking and sensory quality of spelt can be overcome through fermentation processes. However, the autochthonous microbiota of spelt sourdough is poorly known. This study highlights the dynamics of microbial communities involved in sourdough fermentation of spelt and provides the basis for the selection of autochthonous cultures, with the aim of improving the nutritional potential of spelt and its rheology and bread-making properties.

Korcari D ，Ricci G ，Quattrini M ，Fortina MG ... -  《-》

Identification of lactic acid bacteria and yeasts, and characterization of food components of sourdoughs used in Japanese bakeries.

Sourdough is a low-pH, fermented product prepared using lactic acid bacteria and yeast mixed with rye flour, wheat flour, and water. It is used and backslopped in bakeries because it enhances texture, flavor, and dough expansion of bread. Various lactic acid bacteria and yeasts have been identified in sourdough, especially in the West. However, microbial and physical characteristics of sourdough from Japan have not been investigated. Here, we characterized the microbial composition and food component characteristics of sourdough from four bakeries in Kansai region, Japan, and performed sensory and quality evaluation of baguettes enriched with 10% sourdough. We detected different species of lactic acid bacteria such as Lactobacillus brevis, Lactobacillus alimentarius, Lactobacillus pentosus, Lactobacillus vaccinostercus, Lactobacillus sanfranciscensis, and Lactobacillus sakei. The identified yeasts primarily included Saccharomyces cerevisiae, with Candida humilis detected in some samples. Components such as amino acids, lactic acid, acetic acid, ethanol, 3-methyl-1-butanol, ethyl acetate, and phenethyl alcohol differed among samples and distinctively affected flavor, quality, and aroma of sourdough-enriched baguettes. The different species of lactic acid bacteria and the ratio of lactic acid bacteria to yeasts possibly affected food components such as free amino acids, sugars, and organic acids via the Maillard reaction, which influences the savory aromas of bread. Future investigation of the effect of lactic acid bacteria will help to improve the overall quality of bread.

Fujimoto A ，Ito K ，Narushima N ，Miyamoto T ... -  《-》

Biodiversity and technological potential of lactic acid bacteria isolated from spontaneously fermented amaranth sourdough.

Spontaneous fermented sourdoughs prepared from amaranth flour were investigated for the presence of autochthonous lactic acid bacteria (LAB) predominating microbiota. The doughs were fermented with daily backslopping on a laboratory scale at 30°C for 10 days. LAB counts ranged from 2·60 to 8·54 log CFU g(-1) with a pH declined from 6·2 to 3·8 throughout fermentation. The combined use of randomly amplified polymorphic DNA (RAPD)-PCR analysis and sequence analysis of 16S rRNA was applied for LAB intraspecies differentiation and taxonomic identification, respectively. Enterococcus, Pediococcus and Lactobacillus species were present in amaranth sourdoughs (AS). After the first refreshment step, Lactobacillus plantarum dominated AS until the end of fermentation. In coincidence, when DGGE analysis was performed, the occurrence of a progressive change in bacterial communities allowed the selection of Lact. plantarum as a dominant species. Moreover, technological, functional and safety characteristics of representative RAPD-biotypes were investigated. Lact. plantarum CRL1898 was selected as a potential candidate for gluten-free amaranth sourdough starter. Nowadays, there is an increasing interest in ancient noncereal gluten-free (GF) crops such as amaranth, due to their reported nutritional and health benefits. However, the use of these grains is still limited to traditional foods and bread making processes that are not yet well standardized. Results on the dynamics of autochthonous lactic acid bacteria (LAB) microbiota during laboratory spontaneous amaranth sourdoughs (AS) fermentation will contribute to overcome challenges for GF-fermented products development. In addition, knowledge about LAB diversity involving Enterococcus, Pediococcus and Lactobacillus species, with Lactobacillus plantarum predominating during AS fermentation, and their technological and functional properties provides the basis for the selection of autochthonous strains as starters cultures for novel gluten-free bakery products with enhanced nutritional, sensory and/or safety quality.

Ruiz Rodríguez L ，Vera Pingitore E ，Rollan G ，Martos G ，Saavedra L ，Fontana C ，Hebert EM ，Vignolo G ... -  《-》

Bacterial community dynamics in spontaneous sourdoughs made from wheat, spelt, and rye wholemeal flour.

Sourdough fermentation is a traditional process that is used to improve bread quality. A spontaneous sourdough ecosystem consists of a mixture of flour and water that is fermented by endogenous lactic acid bacteria (LAB) and yeasts. The aim of this study was to identify bacterial diversity during backslopping of spontaneous sourdoughs prepared from wheat, spelt, or rye wholemeal flour. Culture-dependent analyses showed that the number of LAB (109  CFU/ml) was higher by three orders of magnitude than the number of yeasts (106  CFU/ml), irrespective of the flour type. These results were complemented by next-generation sequencing of the 16S rDNA V3 and V4 variable regions. The dominant phylum in all sourdough samples was Firmicutes, which was represented exclusively by the Lactobacillales order. The two remaining and less abundant phyla were Proteobacteria and Bacteroidetes. The culture-independent approach allowed us to detect changes in microbial ecology during the 72-hr fermentation period. Weissella sp. was the most abundant genus after 24 hr of fermentation of the rye sourdough, but as the process progressed, its abundance decreased in favor of the Lactobacillus genus similarly as in wheat and spelt sourdoughs. The Lactobacillus genus was dominant in all sourdoughs after 72 hr, which was consistent with our results obtained using culture-dependent analyses. This work was carried out to determine the microbial biodiversity of sourdoughs that are made from wheat, spelt, and rye wholemeal flour and can be used as a source of strains for specific starter cultures to produce functional bread.

Boreczek J ，Litwinek D ，Żylińska-Urban J ，Izak D ，Buksa K ，Gawor J ，Gromadka R ，Bardowski JK ，Kowalczyk M ... -  《MicrobiologyOpen》

Spelt and emmer flours: characterization of the lactic acid bacteria microbiota and selection of mixed starters for bread making.

Coda R ，Nionelli L ，Rizzello CG ，De Angelis M ，Tossut P ，Gobbetti M ... -  《-》