Probiotic-Induced Modulation of Microbiota Composition and Antibiotic Resistance Genes Load, an In Vitro Assessment.

The imbalance of the gut microbiota (GM) is known as dysbiosis and is associated with disorders such as obesity. The increasing prevalence of microorganisms harboring antibiotic resistance genes (ARG) in the GM has been reported as a potential risk for spreading multi-drug-resistant pathogens. The objective of this work was the evaluation, in a fecal culture model, of different probiotics for their ability to modulate GM composition and ARG levels on two population groups, extremely obese (OB) and normal-weight (NW) subjects. Clear differences in the basal microbiota composition were observed between NW and OB donors. The microbial profile assessed by metataxonomics revealed the broader impact of probiotics on the OB microbiota composition. Also, supplementation with probiotics promoted significant reductions in the absolute levels of tetM and tetO genes. Regarding the blaTEM gene, a minor but significant decrease in both donor groups was detected after probiotic addition. A negative association between the abundance of Bifidobacteriaceae and the tetM gene was observed. Our results show the ability of some of the tested strains to modulate GM. Moreover, the results suggest the potential application of probiotics for reducing the levels of ARG, which constitutes an interesting target for the future development of probiotics.

Faecalibacterium hominis Liu et al. 2023 is a later heterotypic synonym of Faecalibacterium duncaniae Sakamoto et al. 2022.

A strain of the recently validated species Faecalibacterium hominis shares 99.0 % 16S rRNA gene sequence similarity with the type strain of Faecalibacterium duncaniae. The aim of this study was to evaluate the taxonomic relationship between F. hominis and F. duncaniae. F. duncaniae JCM 31915T showed 73.0 % digital DNA-DNA hybridization (dDDH) value with F. hominis JCM 39347T. The average nucleotide identity (ANI) value between these two strains was 96.7 %. These results indicate that F. duncaniae JCM 31915T and F. hominis JCM 39347T represent members of the same species. Based on these data, we propose Faecalibacterium hominis as a later heterotypic synonym of Faecalibacterium duncaniae. An emended description is provided.

Spore-forming properties and enhanced oxygen tolerance of butyrate-producing Anaerostipes spp.

OBJECTIVES: Butyrate producing bacteria are promising candidates for next-generation probiotics. However, they are extremely sensitive to oxygen, which is a significant obstacle to their inclusion in food matrices in a viable form. The present study characterized the spore-forming properties and stress tolerance of human gut butyrate-producing Anaerostipes spp. METHODS: Spore formation properties in six species of Anaerostipes spp. were studied by in vitro and in silico tests. RESULTS: Spores were observed from the cells of three species using microscopic analyses, while the remaining three did not form spores under the tested conditions. Spore-forming properties were confirmed by an ethanol treatment. The spores of Anaerostipes caccae were tolerant to oxygen and survived for 15 weeks under atmospheric conditions. Spores tolerated heat stress at 70 °C, but not at 80 °C. An in silico analysis of the conservation of potential sporulation signature genes revealed that the majority of human gut butyrate-producing bacteria were classified as potential spore formers. Comparative genomics revealed that three spore-forming Anaerostipes spp. specifically possessed the spore formation-related genes of bkdR, sodA, and splB, which may be key genes for different sporulation properties in Anaerostipes spp. CONCLUSIONS: The present study demonstrated the enhanced stress tolerance of butyrate producing Anaerostipes spp. for future probiotic application. Presence of specific gene(s) are possibly keys for sporulation in Anaerostipes spp.

Extracellular fructooligosaccharide degradation in Anaerostipes hadrus for co-metabolism with non-fructooligosaccharide utilizers.

Butyrate producing bacteria are one of the major components of the human gut microbiota. Their major metabolite, butyrate, has several beneficial properties for host health. Fructooligosaccharides (FOSs) are well documented prebiotics and are hydrolyzed by intracellular glycoside hydrolase family 32 (GH32) enzyme in several butyrate producers, whereas butyrate producers Anaerostipes hadrus and Anaerostipes butyraticus possess extracellular GH32 enzymes. The present study characterized the extracellular GH32 enzymes in the organisms to consider possible cross-feeding of FOSs with other microbes. Culture supernatant of A. hadrus actively hydrolyzed kestose and nystose, i.e., degrees of polymerization 3 and 4 FOSs, respectively, whereas that of A. butyraticus did not hydrolyzed. When co-cultured with Lacticaseibacillus rhamnosus GG in the presence of nystose, which was negative for growth on the FOSs but positive for growth on FOS degradants, A. hadrus promoted the growth of L. rhamnosus GG, but A. butyraticus did not. The observed negative results in A. butyraticus would be due to the presence of a stop codon in the gene encoding extracellular GH32. Genomic analysis revealed that A. hadrus conserved a single extracellular GH32 enzyme at the species level. The enzyme was phylogenetically distinguished into two groups, but the two groups shared similar FOS degradation properties. The results obtained here suggested that A. hadrus is active for extracellular degradation of FOSs and provides its degradants to other microbes. This study provides a basis of knowledge to understand how ingested FOSs are co-metabolized in gut microbiota.

Genome-based, phenotypic and chemotaxonomic classification of Faecalibacterium strains: proposal of three novel species Faecalibacterium duncaniae sp. nov., Faecalibacterium hattorii sp. nov. and Faecalibacterium gallinarum sp. nov.

Faecalibacterium prausnitzii is one of the most important butyrate-producing bacteria in the human gut. Previous studies have suggested the presence of several phylogenetic groups, with differences at the species level, in the species, and a taxonomic re-evaluation is thus essential for further understanding of ecology of the important human symbiont. Here we examine the phenotypic, physiological, chemotaxonomic and phylogenomic characteristics of six F. prausnitzii strains (BCRC 81047T=ATCC 27768T, A2-165T=JCM 31915T, APC918/95b=JCM 39207, APC942/30-2=JCM 39208, APC924/119=JCM 39209 and APC922/41-1T=JCM 39210T) deposited in public culture collections with two reference strains of Faecalibacterium butyricigenerans JCM 39212T and Faecalibacterium longum JCM 39211T. Faecalibacterium sp. JCM 17207T isolated from caecum of broiler chicken was also included. Three strains of F. prausnitzii (BCRC 81047T, JCM 39207 and JCM 39209) shared more than 96.6 % average nucleotide identity (ANI) and 69.6 % digital DNA-DNA hybridization (dDDH) values, indicating that the three strains are members of the same species. On the other hand, the remaining three strains of F. prausnitzii (JCM 31915T, JCM 39208 and JCM 39210T) were clearly separated from the above three strains based on the ANI and dDDH values. Rather, JCM 39208 showed ANI and dDDH values over the cut-off values of species discrimination (>70 % dDDH and >95-96 % ANI) with F. longum JCM 39211T, whereas JCM 31915T, JCM 39210T and JCM 17207T did not share dDDH and ANI values over the currently accepted cut-off values with any of the tested strains, including among them. Furthermore, the cellular fatty acid patterns of these strains were slightly different from other F. prausnitzii strains. Based on the collected data, F. prausnitzii JCM 31915T, F. prausnitzii JCM 39210T and Faecalibacterium sp. JCM 17207T represent three novel species of the genus Faecalibacterium, for which the names Faecalibacterium duncaniae sp. nov. (type strain JCM 31915T=DSM 17677T=A2-165T), Faecalibacterium hattorii sp. nov. (type strain JCM 39210T=DSM 107841T=APC922/41-1T) and Faecalibacterium gallinarum sp. nov. (type strain JCM 17207T=DSM 23680T=ic1379T) are proposed.

Unique niche-specific adaptation of fructophilic lactic acid bacteria and proposal of three Apilactobacillus species as novel members of the group.

BACKGROUND: Fructophilic lactic acid bacteria (FLAB) found in D-fructose rich niches prefer D-fructose over D-glucose as a growth substrate. They need electron acceptors for growth on D-glucose. The organisms share carbohydrate metabolic properties. Fructobacillus spp., Apilactobacillus kunkeei, and Apilactobacillus apinorum are members of this unique group. Here we studied the fructophilic characteristics of recently described species Apilactobacillus micheneri, Apilactobacillus quenuiae, and Apilactobacillus timberlakei. RESULTS: The three species prefer D-fructose over D-glucose and only metabolize D-glucose in the presence of electron acceptors. The genomic characteristics of the three species, i.e. small genomes and thus a low number of coding DNA sequences, few genes involved in carbohydrate transport and metabolism, and partial deletion of adhE gene, are characteristic of FLAB. The three species thus are novel members of FLAB. Reduction of genes involved in carbohydrate transport and metabolism in accordance with reduction of genome size were the common characteristics of the family Lactobacillaceae, but FLAB markedly reduced the gene numbers more than other species in the family. Pan-genome analysis of genes involved in metabolism displayed a lack of specific carbohydrate metabolic pathways in FLAB, leading to a unique cluster separation. CONCLUSIONS: The present study expanded FLAB group. Fructose-rich environments have induced similar evolution in phylogenetically distant FLAB species. These are examples of convergent evolution of LAB.

[Establishment of Simple and Quick Method to Confirm the Heating History of Milk and Dairy Products].

In Japan, the import quarantine procedure for dairy products was newly introduced in November 2017. The treatment such as 15 sec heating at 72℃ is required for virus inactivation when importing milk or dairy products from the area which is not free from foot and mouth disease. Moreover, the heating history of imported items is also inspected as import quality procedures. The IDF 63 method is known as one of the methods to confirm the heating history of milk by checking the alkaline phosphatase (ALP) activity. However, this procedure is complicated for daily quarantine inspection. Therefore, we attempted the ALP activity measurement based on the amount of fluorescent substance produced by the enzymatic reaction. Milk and dairy products derived from cow, sheep, and goat were tested after various heat treatment conditions. The ALP of heat-treated milk and dairy products derived from these species above were confirmed to be inactivated under substantially the same heat treatment for 15 sec at 72℃. The measurement method established in this study is simpler, faster, and requires smaller amount of sample compared to other methods. Additionally, the method was also applicable to confirm the heating history of various dairy products by making them into suspension.

PCR-based screening, isolation, and partial characterization of motile lactobacilli from various animal feces.

BACKGROUND: Most lactobacilli found in animal intestines are generally non-motile, but there are few exceptions. Our previous work showed that Lactobacillus agilis BKN88, which is a highly motile strain originating from a chicken, takes advantage of motility in gut colonization in murine models, and thus motile lactobacilli likely have unique ecological characteristics conferred by motility. However, the ecology and habitat of gut-derived motile lactobacilli are still rarely understood. In addition, the limited availability of motile Lactobacillus isolates is one of the major obstacles for further studies. To gain insight into the ecology and habitat of the motile lactobacilli, we established a routinely applicable detection method for motile lactobacilli using PCR and subsequent selective isolation in semi-solid MRS medium for the collection of additional motile lactobacilli from animal feces. RESULTS: We applied the PCR detection using motile lactobacilli-specific primers, based on the motor switch protein gene (fliG) of flagella, to 120 animal feces, followed by selective isolation performed using 45 animal feces. As a result, motile lactobacilli were detected in 44 animal feces. In the selective isolation, 29 isolates of L. agilis and 2 isolates of L. ruminis were obtained from 8 animal species. CONCLUSIONS: These results indicated that motile lactobacilli are distributed in different animal species. Moreover, phylogenetic analysis of the L. agilis isolates suggests co-evolution with the host, and adaptation to a particular environmental niche.

Impact of kestose supplementation on the healthy adult microbiota in in vitro fecal batch cultures.

Prebiotics are widely used to shape a balanced microbiota in humans and animals. 1-Kestose (kestose) is one of the major components in commercialized short-chain fructooligosaccharide and is a promising prebiotic for infants. We herein studied the impact of kestose on the healthy adult microbiota in an in vitro fecal batch culture model. Stool samples obtained from seven healthy adults were diluted, inoculated into broth supplemented with or without 0.5% (w/v) kestose (kestose group and control group, respectively), and cultured under anaerobic conditions. Microbiota in the groups and stool samples were analyzed using 16S rRNA gene sequencing. At the phylum level, the kestose group showed increases in Bacteroidetes, whereas the control group showed increases in Proteobacteria. At the species level, Bifidobacterium longum was the only species showing significantly higher levels in the kestose group than in the control group and stool samples. On the other hand, levels of Escherichia coli were significantly higher in the control group than in stool samples, while the levels were not significantly different between the kestose group and stool samples. Quantitative PCR assays also revealed significantly higher levels of B. longum and lower tendency of E. coli in the kestose group than in the control group. These results suggest that supplementation with kestose increased the levels of beneficial microorganism and prevented the growth of risk-associated microorganisms related to disease development. Further interventional studies are needed to understand the health benefits of kestose in adult humans.

In Vitro Evaluation of Different Prebiotics on the Modulation of Gut Microbiota Composition and Function in Morbid Obese and Normal-Weight Subjects.

The gut microbiota remains relatively stable during adulthood; however, certain intrinsic and environmental factors can lead to microbiota dysbiosis. Its restoration towards a healthy condition using best-suited prebiotics requires previous development of in vitro models for evaluating their functionality. Herein, we carried out fecal cultures with microbiota from healthy normal-weight and morbid obese adults. Cultures were supplemented with different inulin-type fructans (1-kestose, Actilight, P95, Synergy1 and Inulin) and a galactooligosaccharide. Their impact on the gut microbiota was assessed by monitoring gas production and evaluating changes in the microbiota composition (qPCR and 16S rRNA gene profiling) and metabolic activity (gas chromatography). Additionally, the effect on the bifidobacterial species was assessed (ITS-sequencing). Moreover, the functionality of the microbiota before and after prebiotic-modulation was determined in an in vitro model of interaction with an intestinal cell line. In general, 1-kestose was the compound showing the largest effects. The modulation with prebiotics led to significant increases in the Bacteroides group and Faecalibacterium in obese subjects, whereas in normal-weight individuals, substantial rises in Bifidobacterium and Faecalibacterium were appreciated. Notably, the results obtained showed differences in the responses among the tested compounds but also among the studied human populations, indicating the need for developing population-specific products.

Fermented foods in a global age: East meets West.

Fermented foods and alcoholic beverages have long been an important part of the human diet in nearly every culture on every continent. These foods are often well-preserved and serve as stable and significant sources of proteins, vitamins, minerals, and other nutrients. Despite these common features, however, many differences exist with respect to substrates and products and the types of microbes involved in the manufacture of fermented foods and beverages produced globally. In this review, we describe these differences and consider the influence of geography and industrialization on fermented foods manufacture. Whereas fermented foods produced in Europe, North America, Australia, and New Zealand usually depend on defined starter cultures, those made in Asia and Africa often rely on spontaneous fermentation. Likewise, in developing countries, fermented foods are not often commercially produced on an industrial scale. Although many fermented products rely on autochthonous microbes present in the raw material, for other products, the introduction of starter culture technology has led to greater consistency, safety, and quality. The diversity and function of microbes present in a wide range of fermented foods can now be examined in detail using molecular and other omic approaches. The nutritional value of fermented foods is now well-appreciated, especially in resource-poor regions where yoghurt and other fermented foods can improve public health and provide opportunities for economic development. Manufacturers of fermented foods, whether small or large, should follow Good Manufacturing Practices and have sustainable development goals. Ultimately, preferences for fermented foods and beverages depend on dietary habits of consumers, as well as regional agricultural conditions and availability of resources.

Characterization of fructooligosaccharide-degrading enzymes in human commensal Bifidobacterium longum and Anaerostipes caccae.

Kestose and nystose are short chain fructooligosaccharides (scFOSs) with degrees of polymerization of 3 and 4, respectively. A previous study revealed that these scFOSs have different growth stimulation properties against two human commensals, i.e. Bifidobacterium longum subsp. longum and butyrogenic Anaerostipes caccae. The present study characterized genes involved in FOS metabolism in these organisms. A. caccae possesses a single gene cluster consisting of four genes, including a gene encoding the putative FOS degradation enzyme sucrose-6-phosphate hydrolase (S6PH). B. longum possesses two gene clusters consisting of three genes each, including genes encoding ß-fructofuranosidase (CscA) and sucrose phosphorylase (ScrP). In A. caccae, the genes were highly transcribed in cells cultured with sucrose or kestose but poorly in cells cultured with glucose or nystose. Heterologously expressed S6PH degraded sucrose and kestose but not nystose. In B. longum, transcription of the genes was high in cells cultured with sucrose or kestose but was poor or not detected in cells cultured with glucose or nystose. Heterologously expressed CscA degraded sucrose, kestose and nystose, but ScrP degraded only sucrose. These data suggested that the different growth stimulation activities of kestose and nystose are due to different substrate specificities of FOS degradation enzymes in the organisms and/or induction activity of the genes in the two scFOSs. This is the first study characterizing the FOS metabolism at the transcriptional level and substrate-specificity of the degradation enzyme in butyrogenic human gut anaerobes.

Pseudofructophilic Leuconostoc citreum Strain F192-5, Isolated from Satsuma Mandarin Peel.

Fructophilic lactic acid bacteria (FLAB), composed of Fructobacillus spp., Lactobacillus kunkeei, and Lactobacillus apinorum, are unique in that they prefer d-fructose over d-glucose as a carbon source. Strain F192-5, isolated from the peel of a satsuma mandarin and identified as Leuconostoc citreum, grows well on d-fructose but poorly on d-glucose and produces mainly lactate and acetate, with trace amounts of ethanol, from the metabolism of d-glucose. These characteristics are identical to those of obligate FLAB. However, strain F192-5 ferments a greater variety of carbohydrates than known FLAB. Comparative analyses of the genomes of strain F192-5 and reference strains of L. citreum revealed no signs of specific gene reductions, especially genes involved in carbohydrate transport and metabolism, in the genome of F192-5. The bifunctional alcohol/acetaldehyde dehydrogenase gene (adhE) is conserved in strain F192-5 but is not transcribed. This is most likely due to a deletion in the promoter region upstream of the adhE gene. Strain F192-5 did, however, ferment d-glucose when transformed with a plasmid containing the allochthonous adhE gene. L. citreum F192-5 is an example of a pseudo-FLAB strain with a deficiency in d-glucose metabolism. This unique phenotypic characteristic appears to be strain specific within the species L. citreum This might be one of the strategies lactic acid bacteria use to adapt to diverse environmental conditions.IMPORTANCE Obligate fructophilic lactic acid bacteria (FLAB) lack the metabolic pathways used in the metabolism of most carbohydrates and differ from other lactic acid bacteria in that they prefer to ferment d-fructose instead of d-glucose. These characteristics are well conserved at the genus or species level. Leuconostoc citreum F192-5 shows similar growth characteristics. However, the strain is metabolically and genomically different from obligate FLAB. This is an example of a strain that evolved a pseudo-FLAB phenotype to adapt to a fructose-rich environment.

Phylogenetic Analyses of pheS, dnaA and atpA Genes for Identification of Weissella confusa and Weissella cibaria Isolated from a South African Sugarcane Processing Factory.

A previous study reported on the isolation of 430 polysaccharide (gum)-producing bacteria from a South African sugarcane processing factory and the identification of isolates by comparative 16S rRNA gene sequencing. A large number of isolates (202) belonged to the genus Weissella and clustered with reference strains of Weissella cibaria and Weissella confusa. In this study, we identified 147 strains as W. cibaria and 55 as W. confusa based on phylogenetic analyses of pheS and dnaA gene sequences of representative isolates. We also included atpA gene sequence analysis of Weissella isolates as potential future phylogenetic marker to differentiate amongst strains of W. cibaria and W. confusa.

Microbial Diversity Profiling of Polysaccharide (gum)-Producing Bacteria Isolated from a South African Sugarcane Processing Factory.

Polysaccharide (gum)-producing bacteria are responsible for severe economic losses in the sugarcane processing industry. Increased polysaccharide levels in raw sugar are normally an indication that biodeterioration occurred in the cane, soon after harvesting. Once in the sugar processing plant, the cell numbers of gum-producing bacteria escalate and may reach levels difficult to control. We have isolated 430 gum-producing bacteria from sugarcane and different sampling points in a South African sugarcane processing factory. As expected, high cell numbers of gum-producing bacteria were isolated from the factory during a time when sugar with a high dextran content was produced. What we did not expect was to find the same species in the factory at a time when sugar with a low dextran content was produced. Phylogenetic analyses of the 16S rRNA gene sequences differentiated the gum-producing bacteria into four genera and nine species. The majority of these isolates belonged to the genus Weissella (47%), followed by members of Bacillus (24%), Leuconostoc (19%) and Lactobacillus (10%). For the first time, we report on the isolation of Weissella confusa, Weissella cibaria and Bacillus amyloliquefaciens from a sugarcane processing factory.

Fructophilic Lactic Acid Bacteria, a Unique Group of Fructose-Fermenting Microbes.

Fructophilic lactic acid bacteria (FLAB) are a recently discovered group, consisting of a few Fructobacillus and Lactobacillus species. Because of their unique characteristics, including poor growth on glucose and preference of oxygen, they are regarded as "unconventional" lactic acid bacteria (LAB). Their unusual growth characteristics are due to an incomplete gene encoding a bifunctional alcohol/acetaldehyde dehydrogenase (adhE). This results in the imbalance of NAD/NADH and the requirement of additional electron acceptors to metabolize glucose. Oxygen, fructose, and pyruvate are used as electron acceptors. FLAB have significantly fewer genes for carbohydrate metabolism than other LAB, especially due to the lack of complete phosphotransferase system (PTS) transporters. They have been isolated from fructose-rich environments, including flowers, fruits, fermented fruits, and the guts of insects that feed on plants rich in fructose, and are separated into two groups on the basis of their habitats. One group is associated with flowers, grapes, wines, and insects, and the second group is associated with ripe fruits and fruit fermentations. Species associated with insects may play a role in the health of their host and are regarded as suitable vectors for paratransgenesis in honey bees. Besides their impact on insect health, FLAB may be promising candidates for the promotion of human health. Further studies are required to explore their beneficial properties in animals and humans and their applications in the food industry.

Lactobacillus paragasseri sp. nov., a sister taxon of Lactobacillus gasseri, based on whole-genome sequence analyses.

Three strains, JCM 5343T, JCM 5344 and JCM 1130, currently identified as Lactobacillus gasseri, were investigated using a polyphasic taxonomic approach. Although these strains shared high 16S rRNA gene sequence similarities with L. gasseri ATCC 33323T (99.9 %), they formed a clade clearly distinct from ATCC 33323T based on whole-genome relatedness. The average nucleotide identity and in silico DNA-DNA hybridization values of these three strains compared to L. gasseri ATCC 33323T were 93.4-93.7 and 53.1-54.1 %, respectively, and both were less than the widely accepted threshold to distinguish two species (95 and 70 %, respectively). The three strains were Gram-stain positive, non-motile, non-spore-forming, catalase-negative and rod-shaped bacteria. They grew at 25-45 °C and in the presence of 2.0 % (w/v) NaCl. The major fatty acids of the three strains were C16 : 0 and C18 : 1 ω9c. Based on phylogenetic analyses of the phenylalanyl-tRNA synthase alpha subunit and RNA polymerase alpha subunit genes, and on phenotypic and chemotaxonomic characteristics, strains JCM 5343T, JCM 5344 and JCM 1130 represent a novel species distinct from L. gasseri, for which we propose the name Lactobacillusparagasseri sp. nov. In addition, a large portion of genomes currently labelled as L. gasseri in the public sequence database should be reclassified as L. paragasseri based on whole-genome relatedness.

Intracellular localization of sirtuin and cell length analysis of Lactobacillus paracasei suggest possible role of sirtuin in cell division and cell shape regulation.

Sirtuin has been associated in prolonging lifespan of different model organisms. It has been shown to have an enzymatic activity of NAD+-dependent protein deacetylation targeting acetylated proteins. To determine targets and possible roles of sirtuin (LpSirA) in the Lactobacillus paracasei BL23, deletion (ΔsirA), sirtuin overexpressor (highsirA) and GFP fusion (highsirA-Venus) strains were generated, and microscopic localization and cell length analysis were done. Microscopic analysis revealed localization of LpSirA at cell division plates, at cell poles and all throughout the cell length in a spiral manner. Cell length analysis revealed that 46.9% of the ΔsirA cells were observed to be shorter (<2 µm), whereas 12.6% of the highsirA cells were observed to be longer (>4 µm) in comparison with the wild-type with only 17.1% short cells and 5.3% long cells. Our results suggest that sirtuin may have an essential role in cell division and cell shape regulation.

The ability of human intestinal anaerobes to metabolize different oligosaccharides: Novel means for microbiota modulation?

Prebiotic oligosaccharides are known to have significant impacts on gut microbiota and are thus widely used to program healthy microbiota composition and activity from infants to the elderly. Bifidobacteria and lactobacilli are among the major target microorganisms of oligosaccharides, but the metabolic properties of oligosaccharides in other predominant gut microbes have not been well characterized. In the present study, we demonstrated the metabolic properties of six oligosaccharides in 31 key gut anaerobes. Bifidobacteria readily metabolized fructooligosaccharide (FOSs) with degree of polymerization (DP) 3, i.e. 1-kestose, but several strains used did not actively metabolize FOSs with DP4 and DP5, i.e. nystose and fructosylnystose. Akkermansia muciniphila, a potential new probiotic against obesity, did not show significant growth with any of the oligosaccharides tested. The butyrate producer Anaerostipes caccae grew well on 1-kestose but poorly on FOS mixtures, whereas it contained 1-kestose at 30%. Bacteroides-Parabacteroides group species were separated into two groups based on oligosaccharide metabolic properties. One group metabolized well most of the oligosaccharides tested, but the others metabolized only 1 or 2 selected oligosaccharides. Oligosaccharide profiles after culturing revealed that Bifidobacterium spp. preferentially metabolized shorter oligosaccharides (DP3) in the mixtures, whereas Bacteroides-Parabacteroides spp. did not show oligosaccharide selectivity for metabolism or rather preferred longer oligosaccharides (>DP4). The fermentation profiles indicated specific links between the microbial end-products and specific gut microbes. Available carbohydrates had a significant impact on the accumulation of amino acid-derived bacterial metabolites (i.e. phenol, p-cresol, indole and skatole) and short chain fatty acids. The results assist in predicting the impact of oligosaccharides in human intervention and gut microbiota modulation.

In vitro and in silico characterisation of Lactobacillus paraplantarum D2-1, a starter culture for soymilk fermentation.

Soymilk contains several functional nutrients and is thus a promising ingredient for production of functional foods. The present research aimed to study starter properties, functional characteristics and safety of Lactobacillus paraplantarum D2-1, a promising starter culture for soymilk fermentation. Strain D2-1 actively fermented soymilk within 24 h but had weak activity of additional acid production after 7 d. Succinate and acetoin, which could be linked to flavour and taste, were accumulated in fermented soymilk. In vitro study revealed that the organism has several beneficial properties, including high survival ability in artificial gastric juice, high abilities of mucus adhesion and biofilm formation and production of γ-aminobutyric acid and conjugated linoleic acid, without any significant risks for consumption. Genome sequencing supported the desirable metabolic properties of the strain. These results indicate that L. paraplantarum D2-1 is a suitable starter for soymilk fermentation and is a promising probiotic candidate that can be used safely.