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

Type III sourdough: Evaluation of biopreservative potential in bakery products with enhanced antifungal activity

The potential biopreservative role of a Type III sourdough (tIII-SD), produced by starter cultures of Fructilactobacillus sanfranciscensis and Lactiplantibacillus plantarum ATCC 8014, was assessed for its antifungal activity in baking applications. Fermentation was carried out using different substrates to enhance the production of antifungal metabolites for 24 and 48 h. The tIII-SD samples were analyzed in relation to pH, total titratable acidity (TTA) and the production of organic acids. The water/salt-soluble extract of the tIII-SD was evaluated in relation to the inhibition potential against key fungi that contaminate bakery products including Penicillium roqueforti, Penicillium chrysogenum and Aspergillus niger. Finally, breads with 10 % of the tIII-SD were prepared and the fungi contamination was evaluated throughout the shelf life period. The lowest pH value in sourdough was obtained from 48-hour fermentation by L. plantarum. The saline extracts exhibited varying degrees of inhibition in the in vitro test; however, the greatest enhancement of this effect was obtained when whole wheat grain flour was used. The tIII-SD crafted from a blend of wheat and flaxseed flours and fermented with F. sanfranciscensis for 48 h (BSWF48h-FS), demonstrated superior performance compared to other formulations. This variant exhibited a total shelf life of 10 days, suggesting that the utilization of tIII-SD could serve as a viable alternative for natural antifungal agents, proving beneficial for the bakery industry.

Bioprospecting of sourdough microbial species from artisan bakeries in the city of Valencia

This work describes the characterization of an artisanal sourdough set of bakeries located in the city of Valencia. Culture-dependent and -independent analyses detected Fructilactobacillus sanfranciscensis, Saccharomyces cerevisiae and Kazachstania humilis as dominant species. Nevertheless, specific technological parameters, including backslopping temperature, dough yield, or the addition of salt affected microbial counting, LAB/Yeast ratio, and gassing performance, favouring the appearance of several species of Lactobacillus sp., Limosilactobacillus pontis or Torulaspora delbrueckii as additional players. Sourdough leavening activity was affected positively by yeast counts and negatively by the presence of salt. In addition, the predominance of a particular yeast species appeared to impact the dynamics of CO2 release. Seven important flavour-active compounds (ethyl acetate, 1-hexanol, 2-penthylfuran, 3-ethyl-2-methyl-1,3-hexadiene, 2-octen-1-ol, nonanal and 1-nonanol) were detected in all samples and together with 3-methyl butanol and hexyl acetate represented more than the 53% of volatile abundancy in nine of the ten sourdoughs analysed. Even so, the specific microbial composition of each sample influenced the volatile profile. For example, the occurrence of K. humilis or S. cerevisiae as dominant yeast influenced the composition of major alcohol species, while F. sanfranciscensis and L. pontis positively correlated with aldehydes and octanoic acid content. In addition, relevant correlations could be also found among different technological parameters and between these, volatile compounds and microbial species. Overall, our study emphasises on how differences in technological parameters generate biodiversity in a relatively small set of artisan sourdoughs providing opportunities for excellence and quality baking products.

Various cold storage-backslopping cycles show the robustness of Limosilactobacillus fermentum IMDO 130101 as starter culture for Type 3 sourdough production

Type 3 sourdoughs, which are starter culture-initiated and subsequently backslopped, are less studied than other sourdough types. Yet, they can serve as a model to assess how competitive starter culture strains for sourdough production are and how the microbial composition of such sourdoughs may evolve over time. In the present study, Limosilactobacillus fermentum IMDO 130101 was used to produce Type 3 sourdoughs, prepared from wheat and wholemeal wheat flours. Therefore, an initial fermentation of the flour-water mixture was performed at 30 °C for 48 h. This was followed by cold storage-backslopping cycles, consisting of refreshments (50 %, v/v), fermentation steps of 16 h, and storage at 4 °C each week, every three weeks, and every six weeks. The microbial dynamics (culture-dependent and -independent approaches) and metabolite dynamics were measured. In all sourdoughs produced, starter culture strain monitoring, following an amplicon sequence variant approach, showed that Liml. fermentum IMDO 130101 prevailed during one month when the sourdoughs were refreshed each week, during 24 weeks when the sourdoughs were refreshed every three weeks, and during 12 weeks when the sourdoughs were refreshed every six weeks. This suggested the competitiveness and robustness of Liml. fermentum IMDO 130101 for a considerable duration but also showed that the strain is prone to microbial interference. For instance, Levilactobacillus brevis and Pediococcus spp. prevailed upon further cold storage and backslopping. Also, although no yeasts were inoculated into the flour-water mixtures, Kazachstania unispora, Torulaspora delbrueckii, and Wickerhamomyces anomalus were the main yeast species found. They appeared after several weeks of storage and backslopping, which however indicated the importance of an interplay between LAB and yeast species in sourdoughs. The main differences among the mature sourdoughs obtained could be explained by the different flours used, the refreshment conditions applied, and the sampling time (before and after backslopping). Finally, the metabolite quantifications revealed continued metabolite production during the cold storage periods, which may impact the sourdough properties and those of the breads made thereof.

Microbial ecology and metabolite dynamics of backslopped triticale sourdough productions and the impact of scale

Triticale (X Triticosecale Wittmack) is a hybrid of wheat (Triticum aestivum L.) and rye (Secale cereale L.), combining the positive attributes of both cereals. However, it has not been exploited for sourdough production yet. Further, the effect of scale on sourdough production has not been investigated systematically up to now. The aims of the present study were to assess the microbial ecology and metabolomic output of eleven spontaneously fermented, backslopped sourdough productions made with triticale flour on a scale of 100, 200, 500, and 1000 g. The acidification profile [pH and total titratable acidity (TTA)], microbial diversity (culture-dependent and culture-independent), metabolite dynamics, and appropriate correlations were determined. After ten fermentation steps, different species of Lactobacillaceae were prevalent in the mature sourdoughs, in particular Latilactobacillus curvatus, Limosilactobacillus fermentum, and Pediococcus pentosaceus. The microbial diversity could be traced back to the grains and was also present in the milling fractions (flour, bran, and shorts). Furthermore, thanks to the use of Illumina-based high-throughput sequencing and an amplicon sequence variant (ASV) approach, the presence of undesirable bacterial groups (bacilli, clostridia, and enterobacteria) during the initial steps of the backslopping cycle was revealed, as well as a finetuned taxonomic diversity of the LAB genera involved. Small sourdough productions (100 and 200 g) selected for a lower species diversity and reached a stable consortium faster than large ones (500 and 1000 g). Although a comparable final pH of 3.6-4.0 was obtained, the TTA of small sourdoughs was lower than that of large ones. Regarding the metabolic output, the simultaneous production of mannitol and erythritol, beyond ethanol and glycerol, could be linked to sourdoughs in which Liml. fermentum was the sole LAB species present. Further, the use of the arginine deiminase pathway by P. pentosaceus and Liml. fermentum was obvious. An appropriate extraction method followed by liquid injection gas chromatography coupled to triple quadrupole tandem mass spectrometry allowed the quantification of interesting volatile organic compounds, such as ethyl lactate. These findings support the inclusion of triticale as a viable alternative to wheat or rye for the production of sourdoughs that can be integrated into bread-making production schemes.

Metabolic Profile of Einkorn, Spelt, Emmer Ancient Wheat Species Sourdough Fermented with Strain of Lactiplantibacillus plantarum ATCC 8014

The continuous development of bakery products as well as the increased demands from consumers transform ancient grains into alternatives with high nutritional potential for modern wheat species. The present study, therefore, follows the changes that occur in the sourdough obtained from these vegetable matrices fermented by Lactiplantibacillus plantarum ATCC 8014 during a 24 h. period. The samples were analyzed in terms of cell growth dynamics, carbohydrate content, crude cellulose, minerals, organic acids, volatile compounds, and rheological properties. The results revealed significant microbial growth in all samples, with an average value of 9 log cfu/g but also a high accumulation of organic acids with the increase in the fermentation period. Lactic acid content ranged from 2.89 to 6.65 mg/g, while acetic acid recorded values between 0.51 and 1.1 mg/g. Regarding the content of simple sugars, maltose was converted into glucose, and fructose was used as an electron acceptor or carbon source. Cellulose content decreased as a result of the solubilization of soluble fibers into insoluble fibers under enzymatic action, with percentages of 3.8 to 9.5%. All sourdough samples had a high content of minerals; the highest of which-Ca (246 mg/kg), Zn (36 mg/kg), Mn (46 mg/kg), and Fe (19 mg/kg)-were recorded in the einkorn sourdough.

Genetic diversity and population structure of Saccharomyces cerevisiae isolated from Turkish sourdough by iPBS-retrotransposons markers

Molecular DNA markers are valuable tools for analyzing genetic variation among yeast from different populations to reveal the genetically different autochthonous strains. In this study, we employed inter-primer binding site (iPBS) retrotransposon polymorphism to assess the genetic variation and population structure of 96 Saccharomyces cerevisiae isolates from four different regions in Turkey. The nine selected iPBS primers amplified 102 reproducible and scorable bands, of which 95.10% were polymorphic with an average of 10.78 polymorphic fragments per primer. The average polymorphism information content and the resolving power were 0.26–3.58, respectively. Analysis of molecular variance (AMOVA) revealed significant (P < 0.001) genetic differences within populations (88%) and between populations (12%). The unweighted pair group mean with arithmetic (UPGMA) dendrogram grouped 96 S. cerevisiae strains into two main clusters, where the highest probability of the data elucidating the population structure was obtained at ΔK = 2. There was not an obvious genetic discrimination of the populations according to geographical regions on UPGMA, supported by principal coordinate analysis. However, the individuals of the closer provinces in each population were more likely to group together or closely. The results indicate that iPBS polymorphism is a useful tool to reveal the genetically diverse autochthonous S. cerevisiae strains that may be important for the production of sourdough or baked goods.

Yeast Biodiversity in Fermented Doughs and Raw Cereal Matrices and the Study of Technological Traits of Selected Strains Isolated in Spain

Bakers use pure microorganisms and/or traditional sourdoughs as the leavening agent for making bread. The performance of each starter and the substances produced by the microorganisms greatly affect the dough rheology and features of breads. Modern sourdoughs inoculated with selected lactic acid bacteria and yeasts are microbiologically stable, safer than traditional sourdoughs, and easy to use. However, the commercial repertoire of baker’s yeasts is still limited. Therefore, there is a demand for new strains of yeast species, capable of conferring distinctive traits to breads made from a variety of agri-food matrices, in the design of innovative starters. In this context, we report the first comprehensive study on yeasts isolated from a wide range of fermented doughs, cereal flours, and grains of Spain. Nine yeast species were identified from 433 isolates, which were distributed among separate clades. Moreover, phenotypic traits of potential technological relevance were identified in selected yeast strains. Mother doughs (MDs) showed the greatest yeast biodiversity, whereas commercial Saccharomyces starters or related and wild strains often dominated the bakery doughs. A metataxonomic analysis of wheat and tritordeum MDs revealed a greater richness of yeast species and percentage variations related to the consistency, flour type, and fermentation time of MDs.

Microbial Ecology of Greek Wheat Sourdoughs, Identified by a Culture-Dependent and a Culture-Independent Approach

The aim of the present study was to assess the microecosystem of 13 homemade spontaneously fermented wheat sourdoughs from different regions of Greece, through the combined use of culture-dependent (classical approach; clustering by Random Amplified Polymorphic DNA-Polymerase Chain Reaction (RAPD-PCR) and identification by PCR species-specific for Lactiplantibacillus plantarum, and sequencing of the 16S-rRNA and 26S-rRNA gene, for Lactic Acid Bacteria (LAB) and yeasts, respectively) and independent approaches [DNA- and RNA-based PCR-Denaturing Gradient Gel Electrophoresis (DGGE)]. The pH and Total Titratable Acidity (TTA) values ranged from 3.64–5.05 and from 0.50–1.59% lactic acid, respectively. Yeast and lactic acid bacteria populations ranged within 4.60–6.32 and 6.28–9.20 log CFU/g, respectively. The yeast: LAB ratio varied from 1:23–1:10,000. A total of 207 bacterial and 195 yeast isolates were obtained and a culture-dependent assessment of their taxonomic affiliation revealed dominance of Lb. plantarum in three sourdoughs, Levilactobacillus brevis in four sourdoughs and co-dominance of these species in two sourdoughs. In addition, Companilactobacillusparalimentarius dominated in two sourdoughs and Fructilactobacillussanfranciscensis and Latilactobacillus sakei in one sourdough each. Lactococcus lactis, Lb. curvatus, Leuconostoc citreum, Ln. mesenteroides and Lb. zymae were also recovered from some samples. Regarding the yeast microbiota, it was dominated by Saccharomyces cerevisiae in 11 sourdoughs and Pichia membranifaciens and P. fermentans in one sourdough each. Wickerhamomyces anomalus and Kazachstania humilis were also recovered from one sample. RNA-based PCR-DGGE provided with nearly identical results with DNA-based one; in only one sample the latter provided an additional band. In general, the limitations of this approach, namely co-migration of amplicons from different species to the same electrophoretic position and multiband profile of specific isolates, greatly reduced resolution capacity, which resulted in only partial verification of the microbial ecology detected by culture-dependent approach in the majority of sourdough samples. Our knowledge regarding the microecosystem of spontaneously fermented Greek wheat-based sourdoughs was expanded, through the study of sourdoughs originating from regions of Greece that were not previously assessed.

A Holistic Review on Euro-Asian Lactic Acid Bacteria Fermented Cereals and Vegetables

Lactic acid fermentation is one of the oldest methods used worldwide to preserve cereals and vegetables. Europe and Asia have long and huge traditions in the manufacturing of lactic acid bacteria (LAB)-fermented foods. They have different cultures, religions and ethnicities with the available resources that strongly influence their food habits. Many differences and similarities exist with respect to raw substrates, products and microbes involved in the manufacture of fermented products. Many of them are produced on industrial scale with starter cultures, while others rely on spontaneous fermentation, produced homemade or in traditional events. In Europe, common LAB-fermented products made from cereals include traditional breads, leavened sweet doughs, and low and non-alcoholic cereal-based beverages, whereas among vegetable ones prevail sauerkraut, cucumber pickles and olives. In Asia, the prevailing LAB-fermented cereals include acid-leavened steamed breads or pancakes from rice and wheat, whereas LAB-fermented vegetables are more multifarious, such as kimchi, sinki, khalpi, dakguadong, jiang-gua, soidon and sauerkraut. Here, an overview of the main Euro-Asiatic LAB-fermented cereals and vegetables was proposed, underlining the relevance of fermentation as a tool for improving cereals and vegetables, and highlighting some differences and similarities among the Euro-Asiatic products. The study culminated in "omics"-based and future-oriented studies of the fermented products.