Constipation is one of the most common gastrointestinal complaints worldwide. The aim of this study was to determine whether edible bifidobacteria (Bifidobacterium longum, B. infantis, B. animalis, B. bifidum, B. adolescentis or B. breve) exhibit interspecies differences in alleviating constipation induced by loperamide in BALB/c mice and to analyse the main reasons for the interspecies differences. BALB/c mice were given bifidobacteria by gavage once per day for 8 days. The primary outcome measures, which included related constipation indicators, and the secondary outcome measures, which included changes in the concentration of short-chain fatty acids in faeces and changes in the faecal flora, were used to evaluate the therapeutic effects of the edible bifidobacteria on constipation. The findings show that the six species of Bifidobacterium differed in their ability to relieve constipation. B. longum, B. infantis and B. bifidum were the most effective in relieving constipation, B. adolescentis and B. breve were partially effective and B. animalis was not effective. Furthermore, edible Bifidobacterium treated constipation by increasing the abundance of Lactobacillus and decreasing the abundance of Alistipes, Odoribacter and Clostridium. Higher concentrations of short-chain fatty acids were found in the faecal samples from the edible Bifidobacterium treatment groups. Meanwhile, an increased concentration of acetic acid could alleviate constipation. In conclusion, edible bifidobacteria exhibit interspecies differences in the alleviation of constipation. Meanwhile, bifidobacteria improved constipation symptoms by increasing the concentration of acetic acid and the relative abundance of Lactobacillus and reducing the content of Alistipes, Odoribacter and Clostridium.

•Several physiological benefits are associated with the consumption of oligosaccharide.•Effects of oligosaccharide diet on gut microbiota of constipated mice.•Oligosaccharide altered the cecal microbiota community structure.The aim of this study was to evaluate the effects of different kinds of oligosaccharides on cecal microbiota. These oligosaccharides were a fructo-oligosaccharide (FOS) formulation consisting of 95% FOS (FOS95), a galacto-oligosaccharide (GOS) formulation consisting of 90% GOS (GOS90), and an isomalto-oligosaccharide (IMO) formulation consisting of 90% IMO (IMO90), at dosages of 0.8, 4, and 8 g/d/kg bw. FOS95, IMO90, and GOS90 were each gavaged to BALB/c mice for 14 days. Sequencing of 16S rDNA amplicons showed that the abundance of Actinobacteria and TM7 dramatically decreased in constipation group. Feeding constipated mice with FOS95, IMO90, and GOS90 resulted in decreased ratio of Firmicutes to Bacteroidetes, and increased abundances of Bifidobacterium, Bacteroides, Rikenella, Lactobacillus, and Clostridium and decreased abundances of Oscillospira, Coprococcus, and Dorea at the genus level. Overall, our results demonstrate that FOS95, IMO90, and GOS90 modulate the cecal microbiome in constipated mice.

•The effect of ultrasound parameters of surimi on acoustic intensity was studied.•The effect of container materials of surimi on acoustic intensity was studied.•Ultrasound can improve the gel strength of surimi.•The effect of ultrasound on secondary structures of myofibrillar protein was investigated.The effects of ultrasound parameters, and of the container materials used for surimi, on acoustic intensity were investigated. The frequency of ultrasound significantly affected the acoustic intensity. However, the relationship between the acoustic intensity and the frequency of the ultrasound device was not linear. The acoustic intensity increased as the height of the media increased. In addition, the acoustic intensity increased initially, but then decreased, as the volume of the media increased. Two container materials were tested: polyvinyl chloride (PVC) film and an aluminum box. The acoustic intensity was decreased significantly by the use of either material. The barrier effect of the aluminum box was weaker than that of the PVC film at lower frequencies, whereas the barrier effect of the PVC film was weaker than that of the aluminum box at higher frequencies. The gel strength of surimi increased with as the acoustic intensity increased when the latter was above a certain level. Changes in the secondary structure of myofibrillar protein were found to cause the increase in the gel strength.

•Non-additive responses of the hydrated potato and rice starches were observed as the water content was increased.•Potato starch and rice starch showed stable dielectric properties at different hydration levels.•The moisture content of the hydrated PS and RS systems strongly affected their microwave-absorbing performance.In the food industry, microwave-based curing and modification represent green, low-energy-consumption techniques for food processing, offering significant advantages. Water, a representative high-dielectric material, can react with many food components; however, few studies on microwave absorption to these components have been reported. In this study, commercially available potato starch and rice starch (the latter a representative cereal starch) were selected as the research materials. Based on vector network analysis of these materials, the bow coaxial probe and improved arch methods were used to study the dielectric properties and microwave reflection loss of the potato starch and rice starch systems, with different hydration levels, at 2.45 GHz. Their absorption behaviour was compared with the classical model to study the absorption properties of the starch systems under different hydration conditions. The results showed that at ambient temperature, potato starch and rice starch had similar dielectric responses, which both showed a steady rise with increasing water content. Therefore, because of their similar dielectric properties, the two systems behaved similarly in the microwave field. However, further experiments found that the microwave absorption properties of both starches differed significantly from that of water: starch–water systems with different compositions varied nonlinearly in their microwave absorption performance, consistently with the “true single layer of water” theory.

Fructooligosaccharides (FOS) are one of the most studied prebiotics, selectively stimulating the growth of health-promoting bacteria in the host. However, there is increasing evidence that commensal gut bacteria, such as Bacteroides fragilis, Clostridium butyricum, Enterobacter cloacae, and even the pathogenic Escherichia coli BEN2908, are also able to metabolize FOS in vitro, and in some cases, FOS displayed adverse effects. Therefore, it is necessary to identify FOS-metabolizing species that are present in the gut. Unlike previous studies focusing on individual strains, this study used the traditional culture method combined with an alignment search on the gut bacteria database established from the Human Microbiome Project (HMP). The alignment results showed that homologous proteins for FOS transporters and glycosidases were distributed in 237 of the 453 strains of gut bacteria. La506 msmK encoding the ATP-binding protein and Aec45 fosGH1 encoding glycoside hydrolase were most widely distributed, in 155 and 55 strains, respectively. Seven of eight strains with both transporters and glycosidases were proven to be capable of metabolizing FOS, while five strains without either transporters or glycosidases were not. Fifteen species isolated from human feces and 11 species from the alignment search were identified to be FOS-metabolizing, of which Cronobacter sakazakii, Marvinbryantia formatexigens, Ruminococcus gnavus, and Weissella paramesenteroides are reported here for the first time. Thus, alignment search combined with the culture method is an effective method for obtaining a global view of the FOS-metabolizing bacteria in the gut and will be helpful in further investigating the relationship between FOS and human gut bacteria.

Fructo-oligosaccharides (FOS) are usually regarded as a type of prebiotic, favorably stimulating the growth of bifidobacteria and lactobacilli. However, they are not the specific substrates for these target species, and other bacteria, such as Streptococcus, Escherichia, and Clostridium, have been shown to be able to utilize FOS. Previous studies have mainly investigated only a few bacteria groups, and few reports analyzed the global effects of FOS on intestinal microbial communities. In this study the effects of FOS on gut bacteria in mice were investigated through a 16S rRNA metagenomic analysis. In the FOS-low group, the abundance of Actinobacteria significantly increased and that of Bacteroidetes decreased after FOS diet (5%) for 3 weeks. In the FOS-high group, Enterococcus was promoted and levels of Bifidobacterium and Olsenella both notably increased after FOS diet (25%) and the microbiota tended to revert to initial structure 2 weeks after FOS treatment ceased. The most striking observation was that Olsenella became a dominant genus comparable with Bifidobacterium after FOS treatment, and one strain of Olsenella, isolated from mice feces, was confirmed, for the first time, to be capable of using FOS. The results indicated that metagenomic analysis was helpful to reveal the FOS effects on the global composition of gut communities and new target for future studies.

Lactulose has been known as a prebiotic that can selectively stimulate the growth of beneficial bifidobacteria and lactobacilli. Recent studies have indicated that Streptococcus mutans, Clostridium perfringens, and Faecalibacterium prausnitzii are also able to utilize lactulose. However, the previous studies mainly focused on the utilization of lactulose by individual strains, and few studies were designed to identify the species that could utilize lactulose among gut microbiota. This study aimed to identify lactulose-metabolizing bacteria in the human gut, using in silico and traditional culture methods. The prediction results suggested that genes for the transporters and glycosidases of lactulose are well distributed in the genomes of 222 of 453 strains of gastrointestinal-tract bacteria. The screening assays identified 35 species with the ability to utilize lactulose, of which Cronobacter sakazakii, Enterococcus faecium, Klebsiella pneumoniae, and Pseudomonas putida were reported for the first time to be capable of utilizing lactulose. In addition, significant correlations between lactulose and galactooligosaccharide metabolism were found. Thus, more attention should be paid to bacteria besides bifidobacteria and lactobacilli to further investigate the relationship between functional oligosaccharides and gut bacteria.

Peanut allergy (PNA) has becoming a non-negligible health concern worldwide. Thus far, allergen-specific immunotherapy aimed at inducing mucosal tolerance has widely been regarded as a major management strategy for PNA. The safety profiles and the intrinsic probiotic properties of lactic acid bacteria (LAB) render them attractive delivery vehicles for mucosal vaccines. In the present study, we exploited genetically modified Lactococcus lactis to produce peanut allergen Ara h 2 via different protein-targeting systems and their immunomodulatory potency for allergic immune responses in mice were investigated. By comparison with the strain expressing the cytoplasmic form of Ara h 2 (LL1), the strains expressing the secreted and anchored forms of Ara h 2 (LL2 and LL3) were more potent in redirecting a Th2-polarized to a non-allergic Th1 immune responses. Induction of SIgA and regulatory T cells were also observed at the local levels by orally administration of recombinant L. lactis. Our results indicate that allergen-producing L. lactis strains modulated allergic immune responses and may be developed as promising mucosal vaccines for managing allergic diseases.

Most bacterial proteins that are destined to leave the cytoplasm are exported across the cell membrane to their sites of function. These proteins are generally exported via the classical secretion pathway, in which the signal peptide plays a central role. However, some bacterial proteins have been found in the extracellular milieu without any apparent signal peptide. As none of the classical secretion systems is involved in their secretion, this occurrence is termed non-classical protein secretion. The mechanism or mechanisms responsible for non-classical secretion are contentious. This review compiles evidence from the debate over whether the release of the non-classically secreted proteins is the result of cell lysis and discusses how these proteins are exported to the exterior of the cell.

A new food-grade expression system was constructed for Bacillus subtilis based on replicative food-grade expression plasmids and auxotrophic complementation. The food-grade B. subtilis host FG01 was created by knockout of the dal locus from the chromosome of B. subtilis 168. Two food-grade expression plasmids pXFGT03 and pXFGT05 were constructed by combining a novel theta-type Bacillus replicon with the B. subtilis endogenous gene dal and P43 promoter; while pXFGT05 was derived from pXFGT03 by deletion of two open reading frames (ORFs) from the original replicon. Upon transformation of FG01 with pXFGT03 or pXFGT05, the host phenotype was complemented on Luria–Bertani agar plates by the plasmid-coded dal gene, which served as a food-grade selection marker for recombinants. Results showed that deletion of the two ORFs had no impact on plasmid replication. A reporter gene bgaB was cloned into pXFGT03 and pXFGT05, respectively, under control of the P43 promoter, and it was successfully expressed in this food-grade expression system. Segregational stabilities of two recombinant plasmids were investigated, and they were fully stable.

Fed-batch and pH-controlled cultures have been widely used for industrial production of probiotics. The aim of this study was to systematically investigate the relationship between the maximum biomass of different homofermentative Lactobacillus and lactate accumulation, and to develop a prediction equation for the maximum biomass concentration in such cultures. The accumulation of the end products and the depletion of nutrients by various strains were evaluated. In addition, the minimum inhibitory concentrations (MICs) of acid anions for various strains at pH 7.0 were examined. The lactate concentration at the point of complete inhibition was not significantly different from the MIC of lactate for all of the strains, although the inhibition mechanism of lactate and acetate on Lactobacillus rhamnosus was different from the other strains which were inhibited by the osmotic pressure caused by acid anions at pH 7.0. When the lactate concentration accumulated to the MIC, the strains stopped growing. The maximum biomass was closely related to the biomass yield per unit of lactate produced (YX/P) and the MIC (C) of lactate for different homofermentative Lactobacillus. Based on the experimental data obtained using different homofermentative Lactobacillus, a prediction equation was established as follows: Xmax − X0 = (0.59 ± 0.02)·YX/P·C.

•We model the relationship between the specific growth rate and osmotic pressure.•A lactic acid removal system to realize high density cultivation is designed.•The anion-exchange resins used must be converted to OH− form.•The culture system is effective in increasing the biomass of lactic acid bacteria.A fed-batch culture of Lactobacillus plantarum was coupled with a lactic acid removal system to achieve high-density cultivation. Different types of anion-exchange resins were evaluated to establish the lactic acid removal system. This system comprised a cell bioreactor fitted with two anion-exchange columns: one for adding anion-exchange resins, converted to the OH− form, to the bioreactor and the other for filtering the resins after adsorption of acid anions. The pH of the culture broth was controlled at between 6.5 and 7.0 by adding anion-exchange resins to remove lactate. In addition, the growth kinetics in the fed-batch and pH-controlled culture were investigated. The well-known Monod equation was modified to describe the relationship between the specific growth rate and the osmotic pressure. In this cultivation system, a cell concentration of 34.5 g L−1 was obtained after 12 h, being about 13.3 and 2.3 times higher respectively than that of a batch culture and a fed-batch and pH-controlled culture without the addition of resins. The proposed culture system was effective in increasing the biomass of lactic acid bacteria.Download high-res image (75KB)Download full-size image