Protective effects of Bifidobacterium bifidum FL-228.1 on dextran sulfate sodium-induced intestinal damage in mice.

PURPOSE: Numerous studies have found that probiotics benefit the intestinal barrier. However, the prophylactic effects of probiotics on the intestinal barrier, i.e., if probiotics exert protective effects in healthy individuals to defend them against harmful elements, have seldomly been reported. The present study aimed to investigate the possible mechanisms of potential strains with the function of preventing intestinal barrier damage. METHODS: This study investigated nine potential probiotic strains using in vitro and in vivo models on their intestinal barrier-protecting properties. Transcriptomic was then employed to decipher the underlying mechanisms of action of the strains. RESULTS: The results showed that the strains, to varying degrees, regulated the ratio of interleukin (IL)-10 and IL-12 in peripheral blood mononuclear cells (PBMCs), increased the transepithelial electrical resistance (TEER) values, and decreased Caco-2 cell monolayers permeability. Correspondingly, the strains showed different prophylactic efficacies in protecting mice from dextran sulfate sodium (DSS)-induced intestinal barrier damage. Remarkably, Bifidobacterium bifidum FL-228.1 (FL-228.1) showed the best prophylactic efficacies in protecting mice from DSS-induced intestinal barrier damage. Further research suggested that FL-228.1 exerted its prophylactic effects by enhancing mucin 2 (Muc2) production and Claudin (Cldn)-4 in the colon. Furthermore, the transcriptomic and protein-protein interactions (PPI) analyses indicated that the inhibition of NLRP3 and the activation of PPARγ and TLR2 could be involved in protecting the intestinal barrier by FL-228.1. CONCLUSION: Bifidobacterium bifidum FL-228.1 may be developed as a promising probiotic for the prevention of intestinal barrier damage via PPARγ/NLRP3/ TLR2 pathways by enhancing Muc2 and Cldn-4.

Effects of different carbon sources on metabolic profiles of carbohydrates in Streptococcus thermophilus during fermentation.

BACKGROUND: Streptococcus thermophilus is a major starter used in the dairy industry and it could improve the flavor of fermented products. It is necessary to improve biomass of S. thermophilus for its application and industrialization. The utilization of carbon sources directly affects the biomass of S. thermophilus. Therefore, the carbohydrate metabolism of S. thermophilus should be investigated. RESULTS: In the present study, metabolic parameters and gene expression of S. thermophilus S-3 with different carbon sources were investigated. The physicochemical results showed that S. thermophilus S-3 had high lactose utilization. Transcriptome analysis found that approximately 104 genes were annotated onto 15 carbohydrate metabolic pathways, of which 15 unigenes were involved in the phosphotransferase system and 75 were involved in the ATP-binding cassette transporter system. In addition, 171 differentially expressed genes related to carbohydrate metabolism were identified. Expression of the galactose metabolism genes lacSZ and galKTEM increased significantly from the lag phase to the mid-exponential growth phase as a result of the global regulator protein, catabolite control protein A (CcpA). The high expression of galK in the mid- to late- phases indicated that the metabolite galactose is re-transported for intracellular utilization. CcpA regulation may also induce high expressions of glycolytic pathway regulated-genes related to lactose utilization, including ldh, fba, eno, pfkA, bglA, pgi, pgm and pyk, producing optimal glycolytic flux and S. thermophilus S-3 growth. CONCLUSION: The present study provides new insights into the carbon metabolism regulation and provide theoretical support for high-density fermentation of S. thermophilus S-3. © 2022 Society of Chemical Industry.

Lactobacillus casei YRL577 combined with plant extracts reduce markers of non-alcoholic fatty liver disease in mice.

Probiotics and plant extracts are considered to prevent the development of non-alcoholic fatty liver disease (NAFLD). The present study explores the effects of using both probiotics and plant extracts on NAFLD. The present study evaluated the effects of plant extracts on lipid droplet accumulation and the growth of probiotics in vitro. A C57BL/6 mouse model was used to examine the effects of probiotics and plant extracts on NAFLD. Body weight and food intake were measured. The levels of serum lipids, oxidative stress and the liver injury index were determined using commercial kits. Haematoxylin and eosin staining, GC and real-time PCR were also used for analysis. The results revealed that administration of Lactobacillus casei YRL577 and L. paracasei X11 with resveratrol (RES) or tea polyphenols (TP) significantly reduced the levels of total cholesterol, TAG and LDL-cholesterol and increased the level of the HDL-cholesterol. The groups of L. casei YRL577 with RES and TP also regulated the liver structure, oxidative stress and injury. Furthermore, L. casei YRL577 with TP exhibited a more positive effect towards improving the NAFLD and increased the concentrations of the butyric acid than other three combined groups. L. casei YRL577 with TP up-regulated the mRNA levels of the farnesoid X receptor and fibroblast growth factor 15 and decreased the mRNA levels of the apical Na-dependent bile acid transporter. These findings showed that L. casei YRL577 + TP-modified genes in the intestinal bile acid pathway improved markers of NAFLD.

Lactobacillus casei YRL577 ameliorates markers of non-alcoholic fatty liver and alters expression of genes within the intestinal bile acid pathway.

Non-alcoholic fatty liver disease (NAFLD) has become the main cause of end-stage liver disease. Probiotics have the potential effect of alleviating NAFLD. The aim of this study was to explore functional probiotics and their underlying mechanisms. The bile salt hydrolase (BSH) activity in thirty-four strains was determined in vitro. Then, C57BL/6 mice were used to explore the effects of probiotics on NAFLD. Body weight and food intake were measured, and serum lipid concentrations, oxidative stress and proinflammatory cytokines levels were determined using commercial kits. The expressions of intestinal bile acid pathway genes were evaluated via real-time PCR. The results showed that Lactobacillus casei YRL577 and L. paracasei X11 had higher BSH activity. L. casei YRL577 significantly reduced liver weight and liver index and could regulate the levels of lipid metabolism, oxidative stress and proinflammatory cytokines as compared with L. paracasei X11. Furthermore, the results indicated that L. casei YRL577 up-regulated the mRNA levels of farnesoid X receptor and fibroblast growth factor 15, whereas down-regulated the mRNA level of apical Na-dependent bile acid transporter. These findings suggested that L. casei YRL577 modified genes in the intestinal bile acid pathway which might contribute to the alleviation of NAFLD.

Short communication: An inducible CRISPR/dCas9 gene repression system in Lactococcus lactis.

Lactococcus lactis, one of the most important probiotic lactic acid bacteria (LAB), is widely used in the dairy industry as a cell factory for recombinant protein production. Currently, a nisin-controlled inducible expression system is used for this purpose and represents the only commercial expression system in LAB. However, the available genetic modification methods are rather limited for modulating gene expression in L. lactis. Here, we developed a 2-plasmid system for gene transcription repression in L. lactis NZ9000 that uses inducible clustered regularly interspaced short palindromic repeats (CRISPR)-dCas9. An inducible promoter Pnisin was used to drive the expression of dCas9 from Streptococcus pyogenes, whereas a strong constitutive promoter P44 drove single guide RNA expression for single or multiple target genes. dCas9 enabled CRISPR interference-mediated silencing of single or multiple target genes with significant reduction of gene expression, up to 99%. In addition, LLNZ_07335, a putative penicillin acylase, was identified as bile salt hydrolase for bile salt resistance in NZ9000 using this system. To our knowledge, this report is the first for a functional gene for bile salt tolerance in L. lactis. Overall, our work introduces a new gene repression tool for various applications in L. lactis or other LAB.

Effect of Preheating Treatment before Defatting on the Flavor Quality of Skim Milk.

Skim milk has a poor flavor due to the lack of fat. Finding ways to improve the flavor quality of skim milk has attracted the attention of more and more researchers. The purpose of this study was to create a skim milk product with good flavor by processing. Briefly, raw milk was treated by preheating at pasteurization (85 °C, 15 s) and ultra-high temperature (UHT) instantaneous sterilization (137-141 °C, 4 s). Subsequently, the sample was centrifuged to remove fat and obtain two kinds of skim milk, namely, PSM (skim milk obtained by preheating at 85 °C, 15 s) and USM (skim milk obtained by preheating at 137-141 °C, 4 s). The results showed that the intensity of the main sensory attributes (overall liking, milk aroma, etc.) and the concentrations of the key flavor compounds (2-heptanone, 2-nonanone, decanal, hexanoic acid, etc.) were significantly higher in the USM (p < 0.05) than that of the PSM and RSM (skim milk without preheating). Principal component analysis (PCA) with E-Nose (electronic nose) showed that the RSM had significant differences in the milk aroma compared with the PSM and USM. Furthermore, it was found that there were good relationships between volatile compounds and sensory attributes by partial least squares regression (PLSR) analysis. These findings provided insights into improving the flavor quality of skim milk by preheating treatment instead of any flavor additives.

Technological characterization of Lactobacillus in semihard artisanal goat cheeses from different Mediterranean areas for potential use as nonstarter lactic acid bacteria.

The potential of 25 Lactobacillus isolates from 8 semihard artisanal goat cheeses manufactured in 4 different Mediterranean areas was examined for use as nonstarter lactic acid bacteria. The isolates were identified using 16S rDNA sequence analysis. Sixteen strains belonged to Lactobacillus paracasei and 9 to Lactobacillus rhamnosus. The isolates were first screened for salt tolerance, exopolysaccharide and diacetyl production, proteolytic and lipolytic activity, and acidification and autolyzing capacities. Most of the lactobacilli displayed strong salt tolerance [20 strains, including 13 of Lb. paracasei and 7 of Lb. rhamnosus, could grow at 6% (wt/vol) salt], low acidification activity (16 strains, including 9 of Lb. paracasei and 7 of Lb. rhamnosus, presented change in pH ≤0.4 U after 6 h of growth), and high autolytic activity (14 strains, including 9 of Lb. paracasei and 5 of Lb. rhamnosus, showed autolysis values ranging between 25 and 65%). Eleven Lb. paracasei and 6 Lb. rhamnosus produced exopolysaccharide, whereas 8 Lb. paracasei and 4 Lb. rhamnosus produced diacetyl. Moreover, 9 Lb. paracasei and 6 Lb. rhamnosus showed proteolytic activity; none of the isolates showed lipolytic activity. Based on the above characteristics, 8 strains were further evaluated for peptidase activity, including aminopeptidase, dipeptidyl aminopeptidase, and dipeptidase activities. The results indicated that all strains showed peptidase activity toward selected substrates. The substrate specificity and extent of peptidase activities were strain-dependent. Four strains (A-3, B-4, D-3, and D-8) presented the best characteristics and represented the most promising nonstarter lactic acid bacteria candidates for use in industrial manufacturing of goat cheese.

Development of a novel loop-mediated isothermal amplification assay for the detection of lipolytic Pseudomonas fluorescens in raw cow milk from north China.

Lipases secreted by psychrotrophic bacteria are known to be heat resistant and can remain active even after the thermal processing of milk products. Such enzymes are able to destabilize the quality of milk products by causing a rancid flavor. Rapid detection of a small amount of heat-resistant lipase-producing psychrotrophic bacteria is crucial for reducing their adverse effects on milk quality. In this study, we established and optimized a novel loop-mediated isothermal amplification (LAMP) assay for the detection of Pseudomonas fluorescens in raw cow milk, as the most frequently reported heat-resistant lipase-producing bacterial species. Pseudomonas fluorescens-specific DNA primers for LAMP were designed based on the lipase gene sequence. Reaction conditions of the LAMP assay were tested and optimized. The detection limit of the optimized LAMP assay was found to be lower than that of a conventional PCR-based method. In pure culture, the detection limit of the LAMP assay was found to be 4.8 × 101 cfu/reaction of the template DNA, whereas the detection limit of the PCR method was 4.8 × 102 cfu/reaction. Evaluation of the performance of the method in P. fluorescens-contaminated pasteurized cow milk revealed a detection limit of 7.4 × 101 cfu/reaction, which was 102 lower than that of the PCR-based method. If further developed, the LAMP assay could offer a favorable on-farm alternative to existing technologies for the detection of psychotrophic bacterial contamination of milk, enabling improved quality control of milk and milk products.

A novel enterocin T1 with anti-Pseudomonas activity produced by Enterococcus faecium T1 from Chinese Tibet cheese.

An enterocin-producing Enterococcus faecium T1 was isolated from Chinese Tibet cheese. The enterocin was purified by SP-Sepharose and reversed phase HPLC. It was identified as unique from other reported bacteriocins based on molecular weight (4629 Da) and amino acid compositions; therefore it was subsequently named enterocin T1. Enterocin T1 was stable at 80-100 °C and over a wide pH range, pH 3.0-10.0. Protease sensitivity was observed to trypsin, pepsin, papain, proteinase K, and pronase E. Importantly, enterocin T1 was observed to inhibit the growth of numerous Gram-negative and Gram-positive bacteria including Pseudomonas putida, Pseudomonas aeruginosa, Pseudomonas fluorescens, Escherichia coli, Salmonella typhimurium, Shigella flexneri, Shigella sonnei, Staphylococcus aureus, Listeria monocytogenes. Take together, these results suggest that enterocin T1 is a novel bacteriocin with the potential to be used as a bio-preservative to control Pseudomonas spp. in food.

Characterization of recombinant Zea mays transglutaminase expressed in Pichia pastoris and its impact on full and non-fat yoghurts.

BACKGROUND: Transglutaminases catalyze post-translational modification of proteins by ε-(γ-glutamyl) links and covalent amide bonds. Research on properties and applications of plant transglutaminases is less developed than in animals and micro-organisms. In a previous study, optimized Zea mays transglutaminase was purified from recombinant Pichia pastoris strain. The main objective of the present study was to characterize this enzyme and assess its effect on the properties of yoghurt. RESULTS: The purified recombinant transglutaminase presented a Km of 3.98 µmol L(-1) and a Vmax of 2711 min(-1) by the fluorometric method. The enzyme was stable after incubation for 30 min below 50 °C and over a broad pH range of 5-8 at -20 °C for 12 h. The results showed that the crosslinking reaction catalyzed by this enzyme could effectively improve the properties of full and non-fat yoghurts. Also, the properties of non-fat yoghurt could be improved similar to the full-fat product by recombinant transglutaminase. CONCLUSION: The application of recombinant transglutaminase in yoghurt indicated that this enzyme could be used as a substitute for microbial transglutaminase in the production of yoghurt, thus providing experimental evidence for the future application of plant transglutaminases in the food industry.

Metabolites 13,14-Dihydro-15-keto-PGE2 Participates in Bifidobacterium animalis F1-7 to Alleviate Opioid-Induced Constipation by 5-HT Pathway.

SCOPE: People suffer from constipation caused by many factors, including constipation (Opioid-Induced Constipation, OIC) during analgesic treatment. Microorganisms may be a potent solution to this problem, but the mechanism is still unclear. METHODS AND RESULTS: Based on models in vivo and in vitro, the potential mechanism involving Bifidobacterium animalis F1-7 (B. animalis F1-7), screened in the previous studies, is explored through non-targeted metabonomics, electrophysiological experiment and molecular level docking. The results showed that B. animalis F1-7 effectively alleviates OIC and promotes the expression of chromogranin A (CGA) and 5-hydroxytryptamine (5-HT). The metabolite 13,14-dihydro-15-keto-PGE2 related to B. animalis F1-7 is found, which has a potential improvement effect on OIC at 20 mg kg BW-1 in vivo. At 30 ng mL-1 it effectively stimulates secretion of CGA/5-HT (408.95 ± 1.18 ng mL-1 ) by PC-12 cells and changes the membrane potential potassium ion current without affecting the sodium ion current in vitro. It upregulates the target of free fatty acid receptor-4 protein(FFAR4/ß-actin, 0.81 ± 0.02). CONCLUSION: The results demonstrate that metabolite 13,14-dihydro-15-keto-PGE2 participated in B. animalis F1-7 to alleviate OIC via the 5-HT pathway.

Milk serum peptidomics revealed the age gelation of direct UHT milk.

Age gelation is undesirable for direct UHT (dUHT) milk, which is closely related to protein hydrolysis. However, little information is available for the role of serum peptides during the age gelation. In this study, the composition and protein morphology of serum phase were characterized by RP-HPLC, ICP-MS and TEM. The results showed significant increases in soluble proteins, free amino acids, calcium, and phosphorus from casein micelles, indicating protein hydrolysis and peptide release into the serum phase. 23,466 peptides derived from caseins and other proteins were identified in serum phase by peptidomics. The serum peptide profiles of age gelation milk changed dramatically. Peptide fingerprinting revealed that plasmin and cathepsin contributed to the protein hydrolysis during age gelation, with a significant increase in their activity observed. 23 characteristic peptides were ultimately selected as potential indicators for age gelation. These findings provide new insights into the age gelation of UHT milk.

The Effect of Nanoscale Modification of Nisin by Different Milk-Derived Proteins on Its Physicochemical Properties and Antibacterial Activity.

Nisin is used as a natural food preservative because of its broad-spectrum antimicrobial activity against Gram-positive bacteria. However, free nisin is susceptible to various factors that reduce its antimicrobial activity. Milk protein, a protein derived from milk, has self-assembly properties and is a good carrier of bioactive substances. In this study, lactoferrin-nisin nanoparticles (L-N), bovine serum albumin-nisin nanoparticles (B-N), and casein-nisin nanoparticles (C-N) were successfully prepared by a self-assembly technique, and then their properties were investigated. The studies revealed that lactoferrin (LF) and nisin formed L-N mainly through hydrophobic interactions and hydrogen bonding, and L-N had the best performance. The small particle size (29.83 ± 2.42 nm), dense reticular structure, and good thermal stability, storage stability, and emulsification of L-N laid a certain foundation for its application in food. Further bacteriostatic studies showed that L-N enhanced the bacteriostatic activity of nisin, with prominent inhibitory properties against Listeria monocytogenes, Staphylococcus aureus, and Bacillus cereus, which mainly disrupted the cell membrane of the bacteria. The above results broaden our understanding of milk protein-nisin nanoparticles, while the excellent antibacterial activity of L-N makes it promising for application as a novel food preservative, which will help to improve the bioavailability of nisin in food systems.

Insights into the starch and proteins molecular structure changes of foxtail millet sourdough: Effect of fermentation from grains of cereal to pre-meal.

This study investigated the effects of foxtail millet sourdough fermentation time (0, 8, 16, and 24 h) on the protein structural properties, thermomechanical, fermentation, dynamic rheological, starch granules crystalline regions molecular mobility, and starch microstructural characteristics. The fermentation led to a significant increase in the concentration of free amino acids from protein hydrolysis. Fourier transform infrared spectroscopy (FTIR) revealed changes in protein secondary structure and the presence of functional groups of different bioactive compounds. The result of thermomechanical properties showed a significant increase in the stability (0.70-0.79 min) and anti-retrogradation ability (2.29-3.14 Nm) of lactic acid bacteria (LAB) sourdough compared to the control dough, showing a wider processing applicability with radar profiler index. In contrast, sourdoughs with lower tan δ values had higher elasticity and strength. Scanning electron microscopy showed that the surface of the starch appeared from smooth to uneven with patchy shapes and cavities, which declined the crystallinity from 34.00 % to 21.57 %, 23.64 %, 25.09 %, and 26.34 % respectively. Fermentation changed the To, Tp, Tc, and ΔH of the starch. The results of the study will have great potential for application in the whole grain sourdough industry.

Whole-genome analysis, evaluation and regulation of in vitro and in vivo GABA production from Levilactobacillus brevis YSJ3.

Gamma-aminobutyric acid (GABA) produced by lactic acid bacteria (LAB) is safe and has several health benefits. Levilactobacillus brevis YSJ3 was selected from 110 LAB. It exhibited the highest in vitro GABA production level of 970.10 µg/mL. Whole-genome analysis revealed that L. brevis YSJ3 contained gadR, gadC, gadB and gadA. Furthermore, the Luedeking-Piret model was fitted, which indicated that GABA production was divided into three stages. The gadR 0079, gadC 0080, and gadB 0081 were confirmed to promote GABA synthesis. Moreover, 55 metabolites, particularly those involved in arginine metabolism, were significantly different at 6 and 20 h of cultivation. Notably, L. brevis YSJ3 significantly improved sleep in mice and increased GABA levels in the mice's gut compared with the control group. This suggests that the oral administration of L. brevis YSJ3 improves sleep quality, probably by increasing intestinal GABA levels. Overall, L. brevis YSJ3 was confirmed as a GABA-producing strain in vitro and in vivo, making it a promising probiotic candidate for its application in food and medicine.

Effect of Fermented Milk Supplemented with Nisin or Plantaricin Q7 on Inflammatory Factors and Gut Microbiota in Mice.

Lactic-acid-bacteria-derived bacteriocins are used as food biological preservatives widely. Little information is available on the impact of bacteriocin intake with food on gut microbiota in vivo. In this study, the effects of fermented milk supplemented with nisin (FM-nisin) or plantaricin Q7 (FM-Q7) from Lactiplantibacillus plantarum Q7 on inflammatory factors and the gut microbiota of mice were investigated. The results showed that FM-nisin or FM-Q7 up-regulated IFN-γ and down-regulated IL-17 and IL-12 in serum significantly. FM-nisin down-regulated TNF-α and IL-10 while FM-Q7 up-regulated them. The results of 16S rRNA gene sequence analysis suggested that the gut microbiome in mice was changed by FM-nisin or FM-Q7. The Firmicutes/Bacteroides ratio was reduced significantly in both groups. It was observed that the volume of Akkermansia_Muciniphila was significantly reduced whereas those of Lachnospiraceae and Ruminococcaceae were increased. The total number of short-chain fatty acids (SCFAs) in the mouse feces of the FM-nisin group and FM-Q7 group was increased. The content of acetic acid was increased while the butyric acid content was decreased significantly. These findings indicated that FM-nisin or FM-Q7 could stimulate the inflammation response and alter gut microbiota and metabolic components in mice. Further in-depth study is needed to determine the impact of FM-nisin or FM-Q7 on the host's health.

Bifidobacterium improves oestrogen-deficiency-induced osteoporosis in mice by modulating intestinal immunity.

Osteoporosis has become one of the major diseases that threaten the health of middle-aged and elderly people, and with the growth of an ageing population, more and more people are affected by osteoporosis these days. In recent years, intestinal flora has been found to affect the host immune system, and an overactive immune system is closely related to bone resorption. Probiotics can effectively improve bone density and strength, reduce bone loss, and improve osteoporosis, but their mechanism of action and relationship with intestinal microbiota are still unclear. In this study, two strains of Bifidobacterium (Bifidobacterium bifidum FL228.1 and Bifidobacterium animalis subsp. Lactis F1-7) that can alleviate intestinal inflammation were screened based on previous experiments. Through the construction of an ovariectomized mouse model, the improvement of osteoporosis by Bifidobacterium was detected, and the influence of Bifidobacterium on intestinal immunity was explored. The results show that Bifidobacterium treatment significantly improved bone mineral density (BMD), bone volume/total volume ratio (BV/TV), and trabecular number (Tb·N), and effectively suppressed bone loss. Furthermore, Bifidobacterium treatment could inhibit the expression of inflammatory cytokines in the gut, alleviate gut inflammation, and thus suppress excessive osteoclast generation. Its mechanism of action includes factors that protect the mucosal barrier, including occludin, ZO-1, claudin-2, and MUC2, and the reduction of pro-inflammatory M1 macrophages. B. bifidum FL228.1 increased the abundance of beneficial bacteria in the colon, including Lactobacillus and Colidextribacter. B. animalis F1-7 increased the abundance of Bifidobacterium and decreased the abundance of Desulfovibrio and Ruminococcus in the colon. These research findings expand our understanding of the gut-bone axis and provide new guidance for the development of probiotic-based therapies for osteoporosis in the future.

Preparation and synbiotic interaction mechanism of microcapsules of Bifidobacterium animalis F1-7 and human milk oligosaccharides (HMO).

Probiotics such as Bifidobacterium spp. generally possess important physiological functions. However, maintaining probiotic viability is a challenge during processing, storage, and digestive transit period. Microencapsulation is widely considered to be an attractive approach. In this study, B. animalis F1-7 microcapsules and B. animalis F1-7-HMO microcapsules were successfully prepared by emulsification/internal gelation with high encapsulation efficiency (90.67 % and 92.16 %, respectively). The current study revealed that HMO-supplemented microcapsules exhibited more stable lyophilized forms and thermal stability. Additionally, a significant improvement in probiotic cell viability was observed in such microcapsules during simulated gastrointestinal (GI) fluids or storage. We also showed that the individual HMO mixtures 6'-SL remarkably promoted the growth and acetate yield of B. animalis F1-7 for 48 h (p < 0.05). The synbiotic combination of 6'-SL with B. animalis F1-7 enhanced SCFAs production in vitro fecal fermentation, decreasing several harmful intestinal bacteria such as Dorea, Escherichia-Shigella, and Streptococcus while enriching the probiotic A. muciniphila. This study provides strong support for HMO or 6'-SL combined with B. animalis F1-7 as an innovative dietary ingredient to bring health benefits. The potential of the synbiotic microcapsules with this combination merits further exploration for future use in the food industry.

Correction: Lactobacillus fermentum F40-4 ameliorates hyperuricemia by modulating the gut microbiota and alleviating inflammation in mice.

Correction for 'Lactobacillus fermentum F40-4 ameliorates hyperuricemia by modulating the gut microbiota and alleviating inflammation in mice' by Jiayuan Cao et al., Food Funct., 2023, 14, 3259-3268, https://doi.org/10.1039/D2FO03701G.

Up-regulation of sortase-dependent pili in Bifidobacterium longum BBMN68 in response to bile stress enhances its adhesion to HT-29 cells.

Adhesion to gastrointestinal tract is crucial for bifidobacteria to exert their probiotic effects. Our previous work found that bile salts significantly enhance the adhesion ability of Bifidobacterium longum BBMN68 to HT-29 cells. In this study, trypsin-shaving and LC-MS/MS-based surface proteomics were employed to identify surface proteins involved in bile stress response. Among the 829 differentially expressed proteins, 56 up-regulated proteins with a fold change >1.5 were subjected to further analysis. Notably, the minor pilin subunit FimB was 4.98-fold up-regulated in response to bile stress. In silico analysis and RT-PCR confirmed that gene fimB, fimA and srtC were co-transcribed and contributed to the biosynthesis of sortase-dependent pili Pil1. Moreover, scanning electron microscopy and immunogold electron microscopy assays showed increased abundance and length of Pil1 on BBMN68 under bile stress. As the major pilin subunit FimA serves as adhesion component of Pil1, an inhibition assay using anti-FimA antibodies further confirmed the critical role of Pil1 in mediating the adhesion of BBMN68 to HT-29 cells under bile stress. Our findings suggest that the up-regulation of Pil1 in response to bile stress enhances the adhesion of BBMN68 to intestinal epithelial cells, highlighting a novel mechanism of gut persistence in B. longum strains.