Lactobacillus Sanfranciscensis Research Articles

Gut Microbiome Derived Lactic Acid Bacteria (GM-d-LAB) from Dwarf Goats (Capra aegagrus hircus) Inhibit the Resident Multiple Antibiotics Resistance Bacterial pathogens

Background: The global health threat posed by antimicrobial resistance (AMR) has created an urgent need for developing alternative treatment methods. Probiotics, especially Lactic Acid Bacteria (LAB), are gaining interest in this context, as they demonstrate health-enhancing effects and potent antimicrobial activities. The intestines of goats could be a potential origin for developing new probiotics applications in animal feed and human health. Hence this study was carried out to determine the antibiotic resistance profiles of LAB and pathogens within the intestines of Nigerian dwarf goats (Capra aegagrus hircus), the antimicrobial activity of LAB against resident MDR pathogens, and subsequent identification of bioactive LAB isolated from goat faeces in Nigeria as potential probiotics in animal feed and human health.
 Method: Selective isolation of the LAB was carried out using de Mann Rogosa Sharpe (MRS) agar while enteric pathogens were isolated on MacConkey agar. Preliminary identification was carried out based on Gram reaction, and morphological, colonial, and biochemical characteristics of each isolate. Antibiotic susceptibility profiles of all isolates were determined using the Kirby-Bauer disc diffusion method. The agar overlay method was used to test the most resistant LAB isolates for antimicrobial activity against enteric pathogens. Selected LAB isolates were identified by 16SrRNA sequencing. 
 Results: The antibiotics susceptibility profile showed that a majority (77%) of LAB isolates and minimal (҇≤10%) of enteric pathogens demonstrated resistance to at least three classes of antibiotics, indicating a pattern of multi-drug resistance. Over half (62%) of these LAB isolates displayed significant antimicrobial activity against at least five of the resident-resistant pathogens, illustrating their potential role in controlling these pathogens. The sequencing results identified the most active LAB isolates, revealing a mix of strains including Pediococcus lolli (46%), Pediococcus pentosaceus (23%), Weissella confusa (8%), Enterococcus faecium (8%), Enterococcus hirae (8%), and Lactobacillus sanfranciscensis (8%).
 Conclusion: The discovery of a diverse range of LAB strains in goat intestines with significant antimicrobial activity against resident enteric pathogens is valuable. This finding suggests the potential use of these bacteria as natural alternatives to traditional antibiotics, especially in the context of growing AMR in animal husbandry.

Chinese traditional sourdough steamed bread made by retarded sponge-dough method: Microbial dynamics, metabolites changes and bread quality during continuous propagation

Continuous propagation of Chinese traditional sourdough (CTS) was adopted to simulate the industrial production of sourdough steamed bread made by retarded sponge-dough method (SSB). Establishment of a stable microbial ecosystem occurred in mature sourdough within four days of continuous propagation, as revealed by both microbial and metabolic analyses. Lactobacillus sanfranciscensis and Kazachstania humilis were the predominant bacterial and fungal species in mature sourdoughs. Their relative abundances changed significantly from the first to third day of continuous propagation while exhibited relatively constant from the fourth day onwards despite the use of flour/water for each back-slopping step. Major changes in the metabolites and fermentative characteristics were observed during the initial three days and dough samples showed little temporal metabolic and fermentative variations from the fourth days onwards. Consequently, volumetric and textural properties as well as the volatile flavor compounds of SSB displayed rather high stability from the fourth day onwards.

Dynamics of Microbiota in Three Backslopped Liquid Sourdoughs That Were Triggered with the Same Starter Strains

The preparation of sourdough may include the use of starter microorganisms to address the fermentation process toward specific conditions. The aim of this work was to study the dynamics of the microbial ecosystem in three liquid sourdoughs (SD1, SD2 and SD3) triggered with the same microbial strains. Lactiplantibacillus plantarum (formerly known as Lactobacillus plantarum), Saccharomyces cerevisiae and Candida lambica strains were inoculated as starters, and sourdoughs were differentiated for the fermentation conditions and for the method of starter inoculation. The analyses were performed on the three sourdoughs propagated in the laboratory for 22 days and on the sample SD1, which was transferred to a bakery and refreshed over many months. The dynamics of microbial communities were studied by plate-count analysis and metataxonomic approach. The acidity of sourdough was evaluated over time. Metataxonomic analysis highlighted a large heterogeneity of fungi microbiota in all sourdough preparations, many of them probably originated from the flour, being pathogens of plants. Few yeast species were found, and S. cerevisiae was plentiful but did not predominate over the other species, whereas the C. lambica species decreased over time and then disappeared in all preparations. The bacterial microbiota was less heterogeneous than the fungi microbiota; the species L. plantarum, Leuconostoc citreum and Levilactobacillus brevis (formerly known as Lactobacillus brevis) were always present in all sourdoughs, whereas Fructilactobacillus sanfranciscensis (formerly known as Lactobacillus sanfranciscensis) became the dominant species in bakery-propagated SD1 and in SD2 at the end of the propagation period.

Interaction between Chocolate Polyphenols and Encapsulated Probiotics during In Vitro Digestion and Colonic Fermentation

This study evaluated the interaction between probiotics and polyphenols in chocolates (45% and 70% cocoa) fortified with encapsulated probiotics. Cocoa powder was used as the main encapsulation component in a Na-alginate plus fructooligosaccharides formulation. Probiotic-chocolates (PCh) were produced by adding 1% encapsulated probiotics to the final mixture. The chocolate samples were subjected to in vitro gastrointestinal digestion and colonic fermentation. The data revealed that the most bioaccessible polyphenols in both formulations of PCh containing 45% and 70% cocoa were released in the gastric digested supernatant. The bioaccessible polyphenols from PCh with 70% cocoa reached 83.22–92.33% and 8.08–15.14% during gastrointestinal digestion and colonic fermentation, respectively. Furthermore, the polyphenols with higher bioaccessibility during colonic fermentation of both PChs developed with the CA1 formulation (cocoa powder 10%, Na-alginate 1% and fructooligosaccharides 2%) were detected in the presence of Streptococcus thermophilus and Lactobacillus sanfranciscensis. The results showed that PCh with specific probiotics favored the bioconversion of a specific polyphenol. For example, chocolate fortified with Lacticaseibacillus casei released larger quantities of epicatechin and procyanidin B1, while Lactiplantibacillus plantarum released more catechin and procyanidin B1 for Lacticaseibacillus rhamnosus LGG. Overall, the study findings concluded that chocolate polyphenols could be utilized by probiotics for their metabolism and modulating the gut, which improved the chocolates’ functionality.

Production of short chain fatty acids and vitamin B12 during the in-vitro digestion and fermentation of probiotic chocolate

The prebiotic functions of chocolate to improve the function and health benefit of the chocolate when enriched with probiotics has not been fully investigated. This study investigated the role of chocolates enriched with probiotics in the production of SCFAs and vitamin B12 during the in-vitro colonic fermentation. Seven probiotic bacteria were encapsulated using a mixture of cocoa powder (10%), FOS (2%) and Na-alginate (1%) before added to chocolates. The results revealed that encapsulated Lactobacillus plantarum and Bifidobacterium animalis spp. lactis BB12 produced significantly higher amounts (1876.5 ± 105.16 and 1348.51 ± 77.37 mmol, respectively) of acetic acid after 48h of colonic fermentation. Chocolates with encapsulated BB12, La5, Lactobacillus sanfranciscensis and Streptococcus thermophilus yielded higher amounts of propionic, isobutyric, butyric and isovaleric acid. Probiotic-chocolates with 70% cocoa produced significantly more acetic, propionic, and butyric acids than that of 45% cocoa. However, Probiotic-chocolates with 45% cocoa produced greater amounts of vitamin B12 than 70% cocoa. These data demonstrate that probiotic-chocolate could be a functional snack with additional health benefits.

Lactic Acid Bacteria Are Prevalent in the Infrabuccal Pockets and Crops of Ants That Prefer Aphid Honeydew.

Ants are evolutionarily successful species and occupy diverse trophic and habitat niches on the earth. To fulfill dietary requirements, ants have established commensalism with both sap-feeding insects and bacteria. In this study, we used high-throughput sequencing of the bacterial 16S rRNA gene to characterize the bacterial composition and structure of the digestive tracts in three species of Formica ants and Lasius niger (Linnaeus)—species that predominantly feed on honeydew secreted by aphids. We found that bacterial communities displayed species- and colony-level signatures, and that bacterial communities in the infrabuccal pockets and crops were different from those in the midguts and hindguts. Lactobacillus and Wolbachia were dominant in the infrabuccal pockets and crops of workers, whereas Wolbachia was dominant in the midguts, hindguts and brood (larvae, pupae and cocoons). To learn more about the dominant Lactobacillus in ants, we assessed its prevalence in a wide range of aphid-tending ants using diagnostic PCR. We found that Lactobacillus was more prevalent in Formicinae than in Myrmicinae species. We also isolated four strains of lactic acid bacteria (Lactobacillus sanfranciscensis, Lactobacillus lindneri, Weissella cibaria and Fructobacillus sp.) from the infrabuccal pockets and crops of aphid-tending ants using a culture-dependent method. Two predominant lactic acid bacterial isolates, Lactobacillus sanfranciscensis (La2) and Weissella cibaria (La3), exhibited abilities in catabolizing sugars (sucrose, trehalose, melezitose and raffinose) known to be constituents of hemipteran honeydew. These findings contribute to further understanding the association between ants, aphids and bacteria, and provide additional information on the function of lactic acid bacteria in ants.

Exploring the relationship between the signal molecule AI-2 and the biofilm formation of Lactobacillus sanfranciscensis

The objective of this study was to investigate the effect of the signal molecule AI-2 on biofilm formation in Lactobacillus sanfranciscensis. We found that the influence of signal molecule AI-2 on strains is related to a variety of physiological metabolic behaviors, such as bacterial growth, morphological characteristics, biofilm development, related gene expression, and bile salt stress tolerance. The survival rates of planktonic and biofilm forms of L. sanfranciscensis were measured after acid, bile salt, and in vitro digestion. The results showed that the biofilm strain had stronger stress resistance. Next, the effects of endogenous and synthetic AI-2 on L. sanfranciscensis growth were compared. The addition of synthetic AI-2 improved L. sanfranciscensis cell density and enhanced bacterial cohesion. Upregulated expression of ftsH was found to promote biofilm formation and growth. AI-2 intervention will improve bile salt tolerance in L. sanfranciscensis. In conclusion, the signal molecule AI-2 is involved in the regulation of biofilm formation and development in L. sanfranciscensis.

In vitro Prebiotic Effect of Bread-Making Process in Inflammatory Bowel Disease Microbiome.

Inflammatory bowel disease (IBD), including its two main categories (Crohn's disease and ulcerative colitis), has been linked both to gut microbiota and to diet. Bread is a daily food that has a potential capacity as a prebiotic. Our aim was to evaluate different bread-making processes and their effect on fecal colonic microbiota in IBD patients. The microbial composition of several sourdoughs and dough samples was analyzed by high-throughput sequencing of 16S and 18S rRNA genes. Three types of bread, which followed different bread-making processes, were in vitro digested and incubated with feces from IBD patients. Changes in gut microbiota were assessed by a quantitative polymerase chain reaction using specific bacterial sequence targets. Short-chain fatty acid production was also analyzed by gas chromatography. Lactobacillus sanfranciscensis was the dominant lactic acid bacteria species found in sourdough and bread doughs prepared using sourdough, whereas Saccharomyces cerevisiae was the most dominant yeast in all groups, especially in bread doughs before baking. Differences in microbial composition in raw bread doughs were more related to the type of dough and elaboration than to fermentation time lengths. The analysis of in vitro fecal incubations with bread conditions revealed an increase in most bacterial groups analyzed and short-chain fatty acid production, both in Crohn's disease and ulcerative colitis samples. Most remarkable increases in short-chain fatty acid production mirrored higher abundances of Roseburia species. The potential prebiotic properties observed were mainly obtained when using a high quantity of bread, regardless of bread type. Overall, this study highlights the bacterial dynamics within the bread-making process and the potential prebiotic effect in IBD patients.

New insights into the antifungal activity of lactic acid bacteria isolated from different food matrices

The anti-mold activity of 397 strains of lactic acid bacteria was evaluated using both the spot method in Petri plates and coculture in liquid medium. The study led to the selection of 34 strains isolated from table olives or olive brines, 15 strains from dairy products, and 10 strains from sourdoughs, all able to inhibit a strain of Penicillium crustosum and/or a strain of Aspergillus section Nidulantes, prevailing in two Calabrian olive brines. Seven representative strains were identified as Lactobacillus pentosus (four strains) and Lactobacillus sanfranciscensis (three strains) and are currently under testing for their antifungal activity during table olive fermentation. This research constitutes an initial contribution to the control of fungal growth and mycotoxin accumulation during table olive fermentation. The selected strains could be used as adjunct cultures in table olive fermentation, allowing for the biological control of table olive safety.

Dynamics of Volatile Compounds in Triticale Bread with Sourdough: From Flour to Bread.

Triticale has been suggested for human consumption due to its valuable nutritional composition. The aim of this study was to evaluate volatile compound dynamics in the technological processes of triticale bread and triticale bread with sourdough prepared using Lactobacillus sanfranciscensis based cultures. Two types of sourdough ready-to-use sourdough and two-stage sourdough were used for bread making. Triticale bread without sourdough was used as a control. Volatile compounds from a headspace of flour blend, sourdough, as well as mixed dough, fermented dough, bread crumb and crust were extracted using solid-phase microextraction (SPME) in combination with gas chromatography/mass spectrometry. Alcohols, mainly 1-hexanol, were the main volatiles in the triticale flour blend, whereas in the headspace of sourdough samples ethyl-acetate, ethanol and acetic acid dominated. Two-stage sourdough after 30 min fermentation showed the highest sum of peak areas formed by 14 volatile compounds, resulting in substrates for further aroma development in bread. A total of 29 compounds were identified in the bread: in the crumb the dominant volatile compounds were alcohols, ketones, acids, but in the crust—alcohols, aldehydes, furans dominated. The use of two-stage sourdough provided a more diverse spectrum of volatile compounds. Such volatile compounds as ethanol, 3-methyl-1-butanol, 2-methyl-1-propanol, 2-hydroxy-2-butanone, 2-methylpropanoic acid, and acetic acid were identified in all the analysed samples in all stages of bread making.

A Species-Specific qPCR Method for Enumeration of Lactobacillus sanfranciscensis, Lactobacillus brevis, and Lactobacillus curvatus During Cocultivation in Sourdough

Lactobacillus sanfranciscensis, Lactobacillus brevis, and Lactobacillus curvatus are frequently isolated from cereal-based fermented foods and are the dominant lactic acid bacteria in Korean sourdough. Detection of the individual species and their enumeration during fermentation are of great importance for maintaining the quality of bakery products. Here, we developed a species-specific quantitative polymerase chain reaction (qPCR) method to monitor the population of these three bacterial species during cocultivation in sourdough. Target genes, including those encoding nucleoside hydrolase, hypothetical protein, and glyoxalase, were selected by MegaBLAST for the detection of L. sanfranciscensis, L. brevis, and L. curvatus, respectively. The specificities of PCR primer sets were verified with qPCR; constant cycle threshold (Ct) values were obtained from mixed genomic DNAs (gDNAs) of target and non-target strains. The qPCR results were unaffected by the sourdough matrix. The cell numbers derived from qPCR were 10–65% higher than those obtained using a conventional plate-counting method. The qPCR standard curves for the three Lactobacillus species were established, and their populations were successfully enumerated during sourdough propagation. This method would enable quantification of three Lactobacillus species during cocultivation in sourdough and provide useful information on microbial commensalism that is essential to obtain high-quality bread.

Intraspecies diversity and genome-phenotype-associations in Fructilactobacillus sanfranciscensis

In this study the intraspecies diversity of Fructilactobacillus (F.) sanfranciscensis (formerly Lactobacillus sanfranciscensis) was characterized by comparative genomics supported by physiological data. Twenty-four strains of F. sanfranciscensis were analyzed and sorted into six different genomic clusters. The core genome comprised only 43,14 % of the pan genome, i.e. 0.87 Mbp of 2.04 Mbp. The main annotated genomic differences reside in maltose, fructose and sucrose as well as nucleotide metabolism, use of electron acceptors, and exopolysacchride formation. Furthermore, all strains are well equipped to cope with oxidative stress via NADH oxidase and a distinct thiol metabolism. Only ten of 24 genomes contain two maltose phosphorylase genes (mapA and mapB). In F. sanfranciscensis TMW 1.897 only mapA was found. All strains except those from genomic cluster 2 contained the mannitol dehydrogenase and should therefore be able to use fructose as external electron acceptor. Moreover, six strains were able to grow on fructose as sole carbon source, as they contained a functional fructokinase gene. No growth was observed on pentoses, i.e. xylose, arabinose or ribose, as sole carbon source. This can be referred to the absence of ribose pyranase rbsD in all genomes, and absence of or mutations in numerous other genes, which are essential for arabinose and xylose metabolism. Seven strains were able to produce exopolysaccharides (EPS) from sucrose. In addition, the strains containing levS were able to grow on sucrose as sole carbon source. Strains of one cluster exhibit auxotrophies for purine nucleotides. The physiological and genomic analyses suggest that the biodiversity of F. sanfranciscensis is larger than anticipated. Consequently, “original” habitats and lifestyles of F. sanfranciscensis may vary but can generally be referred to an adaptation to sugary (maltose/sucrose/fructose-rich) and aerobic environments as found in plants and insects. It can dominate sourdoughs as a result of reductive evolution and cooperation with fructose-delivering, acetate-tolerant yeasts.

Genomic profiling of bacterial and fungal communities and their predictive functionality during pulque fermentation by whole-genome shotgun sequencing

Pulque is a culturally important 4,000-year-old traditional Mexican fermented drink. Pulque is produced by adding fresh aguamiel (agave sap) to mature pulque, resulting in a mixture of microbial communities and chemical compositions. We performed shotgun metagenomic sequencing of five stages of pulque fermentation to characterize organismal and functional diversity. We identified 6 genera (Acinetobacter, Lactobacillus, Lactococcus, Leuconostoc, Saccharomyces and Zymomonas) and 10 species (Acinetobacter boissieri, Acinetobacter nectaris, Lactobacillus sanfranciscensis, Lactococcus lactis, Lactococcus piscium, Lactococcus plantarum, Leuconostoc citreum, Leuconostoc gelidum, Zymomonas mobilis and Saccharomyces cerevisiae) that were present ≥ 1% in at least one stage of pulque fermentation. The abundance of genera and species changed during fermentation and was associated with a decrease in sucrose and increases in ethanol and lactic acid, suggesting that resource competition shapes organismal diversity. We also predicted functional profiles, based on organismal gene content, for each fermentation stage and identified an abundance of genes associated with the biosynthesis of folate, an essential B-vitamin. Additionally, we investigated the evolutionary relationships of S. cerevisiae and Z. mobilis, two of the major microbial species found in pulque. For S. cerevisiae, we used a metagenomics assembly approach to identify S. cerevisiae scaffolds from pulque, and performed phylogenetic analysis of these sequences along with a collection of 158 S. cerevisiae strains. This analysis suggests that S. cerevisiae from pulque is most closely related to Asian strains isolated from sake and bioethanol. Lastly, we isolated and sequenced the whole-genomes of three strains of Z. mobilis from pulque and compared their relationship to seven previously sequenced isolates. Our results suggest pulque strains may represent a distinct lineage of Z. mobilis.

Persistence and Effect of a Multistrain Starter Culture on Antioxidant and Rheological Properties of Novel Wheat Sourdoughs and Bread.

Food consumers make decisions primarily on the basis of a product’s nutritional, functional, and sensorial aspects. In this context, this study evaluated the persistence in sourdough of a multistrain starter culture from laboratory to bakery plant production and the effect of the starter on antioxidant and rheological properties of sourdoughs and derived bread. Lactobacillus sanfranciscensis B450, Leuconostoc citreum B435, and Candida milleri L999 were used as a multispecies starter culture to produce a sourdough subsequently used to modify two traditional sourdoughs to make novel bread with improved health and rheological properties. Both these novel bakery sourdoughs showed the persistence of L. sanfranciscensis B450 and C. milleri L999, and showed a significantly different lactic acid bacteria (LAB) concentration from the traditional sourdoughs. The novel sourdough PF7 M had a higher phenolic content (170% increase) and DPPH (8% increase) than the traditional bakery sourdough PF7 F. The novel sourdough PF9 M exhibited an improvement in textural parameters. Further research would be useful on the bioavailability of bio-active compounds to obtain bread with improved characteristics.

Improving bread aroma using low-temperature sourdough fermentation

To improve the aroma of bread, two aroma-producing yeast isolates from the Chinese liquor starter culture called Daqu, Meyerozyma guilliermondii CGMCC 17606 and Pichia kudriavzevii CGMCC 17607, were combined with Lactobacillus sanfranciscensis DSM20451T, were used for sourdough fermentation at 10, 20, and 30 °C. Volatile aroma compounds in bread crumb were extracted using headspace solid-phase micro-extraction and analyzed using gas chromatography-mass spectrometry and gas chromatography-olfactometry-mass spectrometry. The quality of the final bread was analyzed using sensory evaluation. Addition of sourdough fermented with mixed starters at 10 °C promoted bread aroma, showed increased sensorial qualities, and was preferred by panelists. Acetic acid, 1-octen-3-one, and dimethyl trisulfide, were the most aroma-active compounds in sourdough bread fermented with M. guilliermondii and L. sanfranciscensis, whereas those in sourdough bread fermented with P. kudriavzevii and L. sanfranciscensis were acetic acid, 1-octen-3-one, 2-methoxy-4-vinylphenol, 3-methylthio-propanal, furfural, and 1-(2-furanyl)-ethanone. Reducing the fermentation temperature to 10 °C increased the formation of these key volatiles, as well as other aroma-active compounds, such as 3-methyl-1-butanol, 3-methylbutanal, 2-methyl-1-propanol, 1-octen-3-ol, isogeraniol, benzaldehyde, benzene acetaldehyde, ethyl octanoate, ethyl decanoate, phenylethyl acetate, furfural, and 2-pentylfurane. The amount of furans, pyrazines, and volatiles converted from amino acids in bread crumb also increased with the protein hydrolyzation and amino acid formation in sourdough fermented at 10 °C.

Diverse Microbial Composition of Sourdoughs From Different Origins.

Hundreds of sourdoughs have been investigated in the last decades. However, many studies used a culture-dependent and/or culture-independent microbiological approach [mainly based on denaturing gradient gel electrophoresis (DGGE) of PCR amplicons], seldomly combined with a metabolite target analysis, to characterize the microbial species communities of the sourdoughs examined. Moreover, attention was mainly paid on lactic acid bacteria (LAB) and yeast species. In the present study, distinct household-scale (including an artisan lambic brewery) and artisan bakery-scale backslopped sourdoughs (17 in total), obtained from different regions (Belgium, France, United Kingdom, and USA), were examined through a multiphasic approach, encompassing a culture-dependent analysis [targeting LAB, acetic acid bacteria (AAB), and yeasts], different culture-independent techniques [rRNA-PCR-DGGE, metagenetics, and metagenomics (four bakery sourdoughs)], and metabolite target analysis. It turned out that the microbial species diversity of the sourdoughs was influenced by the house microbiota of the producer. Further, when the producer made use of different flours, the sourdoughs harbored similar microbial communities, independent of the flour used. AAB were only present in the Belgian sourdoughs, which might again be related to the processing environment. Fructilactobacillus sanfranciscensis (formerly known as Lactobacillus sanfranciscensis) was the prevalent LAB species of the eight sourdoughs produced by two of the three bakeries of different countries analyzed. These sourdoughs were characterized by the presence of either Saccharomyces cerevisiae or Kazachstania humilis. Moreover, the presence of Fl. sanfranciscensis was positively correlated with the production of mannitol and negatively correlated with the presence of other LAB or AAB species. Sourdoughs produced in an artisan lambic brewery were characterized by the presence of the yeast species Dekkera anomala and Pichia membranifaciens. One household sourdough was characterized by the presence of uncommon species, such as Pediococcus parvulus and Pichia fermentans. Metagenomic sequencing allowed the detection of many more LAB and AAB species than the other methods applied, which opened new frontiers for the understanding of the microbial communities involved during sourdough production processes.

Role of Kazachstania humilis and Saccharomyces cerevisiae in the strain-specific assertiveness of Fructilactobacillus sanfranciscensis strains in rye sourdough

Sourdough is a common ingredient for baked goods as it improves their texture, shelf life and flavor. One of the dominant key species in type I sourdoughs is Fructilactobacillus sanfranciscensis (formerly Lactobacillus sanfranciscensis), which occurs with a multitude of different strains. Noticeably, this species often shares its habitat with the yeasts Saccharomyces cerevisiae or Kazachstania humilis. It is still unclear, which relationship exists between these organisms and whether it is characterized by coexistence, interaction, or mutualism. In this study, competitiveness of different F. sanfranciscensis strains in rye sourdough was examined and its dependence of co-existing yeasts was explored. In particular, it was investigated whether competitiveness of F. sanfranciscensis strains depends on the presence/absence of S. cerevisiae or K. humilis when co-inoculated in the sourdough. Competitiveness of strains was monitored in rye sourdough using the CRISPR locus length polymorphism (CLLP)—PCR for strain differentiation. It was found that F. sanfranciscensis TMW 1.1150, TMW 1.1221 and TMW 1.1597 were dominant regardless of the presence/absence of both yeast species. Dominance of F. sanfranciscensis TMW 1.392, TMW 1.907 and TMW 1.2137 was significantly and diversely influenced by the presence of S. cerevisiae or K. humilis. F. sanfranciscensis TMW 1.2138 and TMW 1.726 were not able to compete against the other F. sanfranciscensis strains. It was possible to sort the eight strains into three different groups: 1. Strain competitiveness was independent of the presence/absence of yeasts; 2. Strain competitiveness was dependent on yeast species and 3. Strains were not competitive in the presence of strains belonging to group 1 or 2. Interestingly, in fermentations that were not inoculated with any yeast a spontaneous occurrence of S. cerevisiae or K. humilis was observed depending on the synergistic competitiveness of the respective F. sanfranciscensis used. Thus, the level of competitiveness was strain specific and, in some strains, dependent on the presence/absence of specific yeast species.

Dynamics of microbial community and changes of metabolites during production of type Ι sourdough steamed bread made by retarded sponge-dough method.

Dynamics of microbial community and changes of metabolites during production of type Ι sourdough steamed bread made by retarded sponge-dough method (SSB) were studied. Lactobacillus sanfranciscensis and Lactobacillus pontis were the dominant bacterial species. Particularly, relative abundances of Lactobacillus sanfranciscensis were significantly higher than that of other sub-dominant bacterial species. The dominant fungal species were Saccharomyces cerevisiae and Kazachstania humilis, and the latter was the most predominant. A stable bacterial and fungal consortia was established in sponge dough retarded from 12 to 24h and main dough proofed from 30 to 60min. Metabolism preference for maltose of Lactobacillus sanfranciscensis favoured a mutualistic association with maltose-negative Kazachstania humilis, and hence contributing to their competitiveness and dominance. Volatile compounds became more abundant with much more esters as sponge retarding time extended. Probably, the accumulation of organic acids and ethanol contributed mostly to formation of ethyl esters in sponge dough during retarding.

Selection of non-Lactobacillus strains to be used as starters for sourdough fermentation

The suitability of forty-one non-Lactobacillus strains to be used as selected starters for sourdough fermentation was evaluated. According to the data collected, Pediococcus pentosaceus OA1 and S3N3 and Leuconostoc citreum PRO17 were selected based on the optimal acidification and growth performances and the intense proteolytic activity (increase of TFFA up to 80%) on whole wheat flour doughs. A relevant degradation of phytic acid (up to 58%) and the increase of phenols content and scavenging activity (4- and 2-folds, respectively) were also observed. The technological performances were compared to two representative Lactobacillus strains (Lactobacillus plantarum and Lactobacillus sanfranciscensis). The investigation of the robustness of the selected strains during the propagation (back-slopping procedure) showed their long-term dominance only when singly-inoculated; while Leuc. citreum PRO17 dominated the fermentation when the strains were co-inoculated. The sourdoughs obtained by the non-Lactobacillus selected strains (singly or pooled) were used for breadmaking. Selected sourdoughs allowed the production of breads characterized by in-vitro protein digestibility (IVPD) higher than that of breads obtained with Lactobacillus strains or baker's yeast. The aroma profile, estimated by GC/MS, was complex and characterized by high concentration of the typical compounds (hexanol, 3-methylbutanol and 2-pentylfuran) of sourdough bread.

Use of physiological and transcriptome analysis to infer the interactions between Saccharomyces cerevisiae and Lactobacillus sanfranciscensis isolated from Chinese traditional sourdoughs

This study aimed to explore the interaction between Saccharomyces cerevisiae and Lactobacillus sanfranciscensis during sourdough fermentation based on metabolic characteristics and transcriptional changes in pure and mixed cultures. Dough was prepared by using these species either as single cultures, or in combination. The cell counts, acidity and volatile compounds in sourdough samples were determined. The growth of S. cerevisiae and L. sanfranciscensis remained unaffacted in mixed culture. In addition, production of some volatile compounds, mainly associated with S. cerevisiae (ethanol, 2,3-pentanedione, 3-methyl-1-butanol, phenylethyl alcohol and 2-methyl-1-propanol) was negatively affected in mixed culture. On the other hand, S. cerevisiae stimulated the acetic acid production by L. sanfranciscensis, but did not have a significant effect on other metabolic traits of L. sanfranciscensis. The transcriptional profile of S. cerevisiae in pure and mixed cultures was analyzed using RNA sequencing. The results showed a significant effect of co-fermentation on S. cerevisiae carbohydrate and amino acids metabolism. The glycerol synthesis, arginine metabolism and glutamate metabolism increased, while the synthesis of ethanol and acetic acid and glutathione metabolism decreased in mixed culture when compared with results obtained from pure culture of S. cerevisiae.