Gut microbiota: a superior operator for dietary phytochemicals to improve atherosclerosis.

Mounting evidence implicates the gut microbiota as a possible key susceptibility factor for atherosclerosis (AS). The employment of dietary phytochemicals that strive to target the gut microbiota has gained scientific support for treating AS. This study conducted a general overview of the links between the gut microbiota and AS, and summarized available evidence that dietary phytochemicals improve AS via manipulating gut microbiota. Then, the microbial metabolism of several dietary phytochemicals was summarized, along with a discussion on the metabolites formed and the biotransformation pathways involving key gut bacteria and enzymes. This study additionally focused on the anti-atherosclerotic potential of representative metabolites from dietary phytochemicals, and investigated their underlying molecular mechanisms. In summary, microbiota-dependent dietary phytochemical therapy is a promising strategy for AS management, and knowledge of "phytochemical-microbiota-biotransformation" may be a breakthrough in the search for novel anti-atherogenic agents.

The recent advances of glucosinolates and their metabolites: Metabolism, physiological functions and potential application strategies.

Glucosinolates and their metabolites from Brassicaceae plants have received widespread attention due to their anti-inflammatory effects. Glucosinolates occurs an "enterohepatic circulation" in the body, and the glucosinolates metabolism mainly happens in the intestine. Glucosinolates can be converted into isothiocyanates by intestinal bacteria, which are active substances with remarkable anti-inflammatory, anti-cancer, anti-obesity and neuroprotective properties. This biotransformation can greatly improve the bioactivities of glucosinolates. However, multiple factors in the environment can affect the biotransformation to isothiocyanates, including acidic pH, ferrous ions and thiocyanate-forming protein. The derivatives of glucosinolates under those conditions are usually nitriles and thiocyanates, which may impair the potential health benefits. In addition, isothiocyanates are extremely unstable because of an active sulfhydryl group, which limits their applications. This review mainly summarizes the classification, synthesis, absorption, metabolism, physiological functions and potential application strategies of glucosinolates and their metabolites.

Ellagic acid and intestinal microflora metabolite urolithin A: A review on its sources, metabolic distribution, health benefits, and biotransformation.

Foods rich in ellagic tannins are first hydrolyzed into ellagic acid in the stomach and small intestine, and then converted into urolithins with high bioavailability by the intestinal flora. Urolithin has beneficially biological effects, it can induce adipocyte browning, improve cholesterol metabolism, inhibit graft tumor growth, relieve inflammation, and downregulate neuronal amyloid protein formation via the ß3-AR/PKA/p38MAPK, ERK/AMPKα/SREBP1, PI3K/AKT/mTOR signaling pathways, and TLR4, AHR receptors. But differences have been reported in urolithin production capacity among different individuals. Thus, it is of great significance to explore the biological functions of urolithin, screen the strains responsible for biotransformation of urolithin, and explore the corresponding functional genes. Tannin acyl hydrolase can hydrolyze tannins into ellagic acid, and the genera Gordonibacter and Ellagibacter can metabolize ellagic acid into urolithins. Therefore, application of "single bacterium", "single bacterium + enzyme", and "microflora" can achieve biotransformation of urolithin A. In this review, the source and metabolic pathway of ellagic tannins, and the mechanisms of the biological function of a metabolite, urolithin A, are discussed. The current strategies of biotransformation to obtain urolithin A are expounded to provide ideas for further studies on the relationship between urolithin and human health.

Absorption, metabolism, bioactivity, and biotransformation of epigallocatechin gallate.

Epigallocatechin gallate (EGCG), a typical flavone-3-ol polyphenol containing eight free hydroxyl groups, is associated with a variety of bioactivities, such as antioxidant, anti-inflammatory, anti-cancer, and antibacterial activities. However, the poor bioavailability of EGCG restricts its use. In this review, we discuss the processes involved in the absorption and metabolism of EGCG, with a focus on its metabolic interactions with the gut microbiota. Next, we summarize the bioactivities of some key metabolites, describe the biotransformation of EGCG by different microorganisms, and discuss its catabolism by specific bacteria. A deeper understanding of the absorption, metabolism, and biotransformation of EGCG may enable its disease-preventive and therapeutic properties to be better utilized. This review provides a theoretical basis for further development and utilization of EGCG and its metabolites for improving the gut microbiota and physiological health.

Recent updates in anti-glycation strategies: selection of natural products and lactic acid bacteria as potential inhibitors based on the multi-pathway anti-glycation targets.

The prevalence of high-sugar diets and unhealthy habits exacerbates the production of advanced glycation end products (AGEs) in the body. When AGEs excessively accumulate in the body, they accelerate the aging process while directly or indirectly causing other complications that can seriously damage the body. Prevention of glycation damage is gaining increasing attention; however, a systematic strategy to combat glycation and specific glycation inhibitors is still lacking. By analyzing the process of glycation damage, we suggest that glycation damage can be mitigated by the inhibition of AGEs production, binding to proteins, and binding to receptors for advanced glycation end products, as well as the attenuation of downstream linkage reactions. This review summarizes the process of glycation damage. According to each step of the process, the review presents the corresponding anti-glycation strategies. Based on recent anti-glycation studies, we support the fabrication of glycation inhibitors by using natural plant products and fermentation products of lactic acid bacteria that partially exhibit anti-glycation properties. This review summarizes the mechanisms by which these dietary ingredients perform anti-glycation functions, providing relevant research evidence. We hope that this review will support and assist subsequent investigations in the development of anti-glycation inhibitors.

Recent advance in quality preservation of non-thermal preservation technology of fresh mushroom: a review.

Fresh mushrooms have a long history of cultivation and consumption, but high postharvest losses are a concern in the commercial production of mushrooms worldwide. Thermal dehydration is widely used in the preservation of commercial mushrooms, but the flavor and taste of mushrooms are significantly altered after dehydration. Non-thermal preservation technology, which effectively maintains the characteristics of mushrooms, is a viable alternative to thermal dehydration. The objective of this review was to critically assess the factors affecting fresh mushroom quality after preservation is remarkable, with the ultimate goal of developing and promoting non-thermal preservation technology for preserving fresh mushroom quality, effectively extending the shelf life of fresh mushrooms. The factors influencing the quality degradation process of fresh mushrooms discussed herein include the internal factors associated with the mushroom itself and the external factors associated with the storage environment. We present a comprehensive discussion of the effects of different non-thermal preservation technologies on the quality and shelf life of fresh mushrooms. To prevent quality loss and extend the shelf life after postharvest, hybrid methods, such as physical or chemical techniques combined with chemical techniques, and novel nonthermal technologies are highly recommended.

Improvement of inflammatory bowel disease by lactic acid bacteria-derived metabolites: a review.

Lactic acid bacteria (LAB) plays a crucial role in the establishment and maintenance of host health, as well as the improvement of some diseases. One of the major modes is the secretion of metabolites that may be intermediate or end products of the LAB's metabolism. In this review, we summarized some common metabolites (particularly short-chain fatty acids [SCFAs], bacteriocin, and exopolysaccharide [EPS]) from LAB in fermented foods and the gut for the first time. The effects of LAB-derived metabolites (LABM) on inflammation, oxidative stress, the intestinal barrier, and gut microbiota in inflammatory bowel disease (IBD) model are also discussed. The discovery of LABM and identification of IBD biomarkers are mainly attributed to the development of metabolomics technologies, especially nuclear magnetic resonance (NMR), gas chromatography-mass spectrometry (GC-MS), and liquid chromatography tandem mass spectrometry (LC-MS). The application of these metabolomics technologies in identification of LABM and IBD biomarkers are also summarized and analyzed. Although the beneficial effects of some LABM have been explored, undiscovered metabolites and their functions still need further investigations.

Exploring the Dose-Effect Relationship of Bifidobacterium longum in Relieving Loperamide Hydrochloride-Induced Constipation in Rats through Colon-Released Capsules.

Constipation is a common disease affecting humans. Bifidobacterium longum is reportedly effective in relieving constipation. Current studies generally focus on the dose-response relationship of oral doses; however, the dose-effect relationship of B. longum in the colon, which is the primary site where B. longum exerts constipation-relieving effects, to treat constipation has not been studied. Herein, three strains of B. longum (FGSZY6M4, FJSWXJ10M2, and FSDJN6M3) were packaged in colon-released capsules to explore the dose-effect relationship in the colon. For each strain, three groups of capsules (104, 106, and 108 CFU/capsule, respectively) and one group of free probiotics (108 CFU/mL) were used to explore the colonic dose effect of B. longum. The results showed that the three strains of B. longum improved fecal water content and promoted intestinal motility by regulating gastrointestinal peptide (MTL, GAS, and VIP), aquaporin-3, and 5-hydroxytryptamine levels while promoting gastrointestinal motility and relieving constipation by regulating the intestinal flora composition of constipated rats and changing their metabolite content (short-chain fatty acids). Among the three free bacterial solution groups (108 CFU/mL), FGSZY6M4 was the most effective in relieving constipation caused by loperamide hydrochloride in rats. The optimal effective dose of each strain was 6M4 (104 CFU/day), 10M2 (106 CFU/day), and S3 (108 CFU/day) of the colon-released capsules. Therefore, for some effective strains, the dose of oral probiotics can be reduced by colon-released capsules, and constipation can be relieved without administering a great number of bacterial solutions. Therefore, investigating the most effective dose of B. longum at the colon site can help to improve the efficiency of relieving constipation.

Mitigation of Dextran-Sodium-Sulfate-Induced Colitis in Mice through Oral Administration of Microbiome-Derived Inosine and Its Underlying Mechanisms.

BACKGROUND: Colonic and serum inosine are significantly reduced in patients with inflammatory bowel disease (IBD). METHODS: This study aimed to explore whether microbiome-derived inosine alleviates colitis and its underlying mechanisms. RESULTS: An inosine intervention effectively improved the clinical signs in colitis mice, suppressed inflammatory cytokines (tumor necrosis factor-alpha (TNF-α), interleukin-6 (IL-6), and IL-1ß) by regulating the nuclear factor-kappa B (NF-κB) pathway, and elevated the activities of anti-oxidative enzymes (including superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px)) by regulating the nuclear factor erythroid-2 related factor 2 (Nrf2) pathway. Additionally, the inosine intervention significantly elevated the expression of tight junction proteins (ZO-1, occudin, and claudin-1) in mice with colitis. High-throughput sequencing revealed that the inosine intervention also prevented gut microbiota disorder by increasing the abundance of beneficial bacteria (Lachnospiraceae NK4A136 group, Romboutsia, Marvinbryantia, Clostridium sensu stricto 1, and Bifidobacterium) and reducing the abundance of harmful bacteria (Pseudomonas, Acinetobacter, and Tyzzerella) in mice with colitis. CONCLUSIONS: Inosine played a significant role in mitigating colitis-related intestinal barrier injury and could potentially be used for therapy in clinical practice.

Broccoli seed extract rich in polysaccharides and glucoraphanin ameliorates DSS-induced colitis via intestinal barrier protection and gut microbiota modulation in mice.

BACKGROUND: Broccoli has received widespread attention because of its anti-inflammatory and antioxidant effects. The present study aimed to explore the composition of broccoli seed extract (BSE) and its effect on colitis induced by dextran sulfate sodium (DSS). RESULTS: BSE mainly comprises glucoraphanin and polysaccharides composed of arabinose, galactose, glucose and mannose. Animal experiments suggested that BSE intervention effectively reversed body weight loss, suppressed the levels of proinflammatory interleukin-6, tumor necrosis factor-α and interleukin-1ß, and elevated the levels of anti-inflammatory interleukin-10 and the activities of superoxide dismutase and glutathione in DSS-induced colitis mice. According to histopathologic and immunohistochemical analysis of colon tissue, BSE intervention may repair the intestinal barrier by upregulating mRNA levels and the expression of tight junction proteins (claudin-1, occludin and zonula occludens-1). Gas chromatography-mass spectrometry (MS) analysis demonstrated that cecal short-chain fatty acids in mice with BSE administration were significantly increased compared with the model group. Sulforaphane and sulforaphane-N-acetylcysteine were only detected in BSE group mice by ultra-performance liquid chromatography-MS analysis. In addition, BSE intervention evidently increased the abundance of Alistipeds, Coriobacteriaceae UCG-002 and Bifidobacterium and decreased the abundance of Escheichia-Shinella, Lachnospiraceae others, Parabacteroides, Ruminococcaceae others and Turicibacter, which possibly promoted carbohydrate metabolism and short-chain fatty acid production. CONCLUSION: The present study aimed to elucidate the effect of BSE on colitis and found that BSE, as a novel food ingredient, has great potential for the improvement of colitis. © 2022 Society of Chemical Industry.

Intestinal microbiomics and hepatic metabolomics insights into the potential mechanisms of probiotic Bifidobacterium pseudolongum CCFM1253 preventing acute liver injury in mice.

BACKGROUND: Bifidobacterium pseudolongum is widely exists in mammal gut and its abundance is associated with human and animal health. The present study aimed to investigate the potential mechanisms of B. pseudolongum CCFM1253 on protecting against lipopolysaccharide (LPS)-induced acute liver injury (ALI) by metagenomic analysis and liver metabolomic profiles. RESULTS: Bifidobacterium pseudolongum CCFM1253 preintervention remarkably attenuated the influence of LPS on serum alanine transaminase and aspartate amino transferase activities. B. pseudolongum CCFM1253 preintervention remarkably attenuated the inflammation responses (tumor necrosis factor-α, interleukin-1ß, and interleukin-6) and elevated antioxidative enzymes activities [total antioxidant capacity, superoxide dismutase, catalase, and glutathione peroxidase] in ALI mice by intervening in the Nf-kß and Nrf2 pathways, respectively. Bifidobacterium pseudolongum CCFM1253 treatment elevated the proportion of Alistipes and Bifidobacterium, and decreased the proportion of uncultured Bacteroidales bacterium, Muribaculum, Parasutterella and Ruminococcaceae UCG-010 in ALI mice, which were strongly correlated with the inhibition of inflammation responses and oxidative stress. Untargeted liver metabolomics exhibited that the hepatoprotective efficacy of B. pseudolongum CCFM1253 might be achieved by altering liver metabolites-related riboflavin metabolism, phenylalanine metabolism, alanine, citrate cycle (tricarboxylic acid cycle), and so on. Furthermore, riboflavin exposure could control the contents of malondialdehyde, superoxide dismutase, and catalase in hydrogen peroxide-treated HepG2 cells. CONCLUSION: Bifidobacterium pseudolongum CCFM1253 can effectively alleviate inflammatory response and oxidative stress, and regulate the intestinal microbiota composition and liver metabolism, and elevate the liver riboflavin content in LPS-treated mice. Therefore, B. pseudolongum CCFM1253 could serves as a potential probiotic to ameliorate the host health. © 2023 Society of Chemical Industry.

Population genomics of Lacticaseibacillus paracasei: pan-genome, integrated prophage, antibiotic resistance, and carbohydrate utilization.

Lacticaseibacillus paracasei has beneficial effects on human health and holds promising potential as a probiotic for use in the development of functional foods, especially dairy products. This species can adapt to a variety of ecological niches and presents fundamental carbohydrate metabolism and tolerance to environmental stresses. However, the population structure, ecology, and antibiotic resistance of Lc. paracasei in diverse ecological niches are poorly understood. Reclassification of Lc. paracasei as a separate species of Lacticaseibacillus has stimulated renewed interest in its research, and a deeper interpretation of it will be important for screening strains beneficial to human health. Here, we collected 121 self-isolated and 268 publicly available Lc. paracasei genomes discussed how genomic approaches have advanced our understanding of its taxonomy, ecology, evolution, diversity, integrated prophage-related element distribution, antibiotic resistance, and carbohydrate utilization. Moreover, for the Lc. paracasei strains isolated in this study, we assessed the inducibility of integrated prophages in their genomes and determined the phenotypes that presented tolerance to multiple antibiotics to provide evidence for safety evaluations of Lc. paracasei during the fermentation processes.

Inhibitory effect of Lactobacillus gasseri CCFM1201 on Gardnerella vaginalis in mice with bacterial vaginosis.

Gardnerella vaginalis is the core pathogen of bacterial vaginosis (BV), the most common vaginal infection in women. G. vaginalis exerts pathogenicity through various factors, such as biofilm formation and the local host immune response stimulation. Therefore, this study aimed to evaluate the inhibitory effect of Lactobacillus gasseri CCFM1201 on G. vaginalis using experimental BV models. We evaluated L. gasseri in vitro to inhibit pathogen biofilm formation and adhesion capacity in HeLa cells using crystal violet staining. Further in vivo studies were conducted to assess the inhibitory effects of L. gasseri CCFM1201 on BV induced by G. vaginalis. L. gasseri exhibited strain-specific adhesion and inhibition of pathogen biofilm formation in vitro. L. gasseri CCFM1201 significantly reduced G. vaginalis in mice (p < 0.05), inhibited sialidase activity, modulated tumor necrosis factor-α and interleukin-1ß expression, and reduced myeloperoxidase activity (p < 0.05). Histopathological examination indicated that L. gasseri CCFM1201 improved inflammatory cell infiltration of vaginal tissue and restored its structure. Vaginal epithelial cell exfoliation, the main clinical feature of BV, was significantly improved by L. gasseri CCFM1201 intervention (p < 0.05). Thus, L. gasseri CCFM1201 is a potential candidate for treating G. vaginalis-induced vaginal diseases.

Anti-aging effects and mechanisms of anthocyanins and their intestinal microflora metabolites.

Aging, a natural and inevitable physiological process, is the primary risk factor for all age-related diseases; it severely threatens the health of individuals and places a heavy burden on the public health-care system. Thus, strategies to extend the lifespan and prevent and treat age-related diseases have been gaining increasing scientific interest. Anthocyanins (ACNs) are a subclass of flavonoids widely distributed in fruits and vegetables. Growing evidence suggests that ACNs delay aging and relieve age-related diseases. However, owing to the low bioavailability of ACNs, their gut metabolites have been proposed to play a critical role in mediating health benefits. In this review, we introduce the biological fate of ACNs after consumption and highlight ACNs metabolites (phenolic acids) from intestinal microorganisms. Additionally, ACNs and gut metabolites exhibit outstanding anti-aging ability in Caenorhabditis elegans, Drosophila melanogaster, and mouse models, probably associated with increasing antioxidation, anti-inflammation, protein homeostasis, antiglycation, mitochondrial function, and inhibition of insulin/IGF-1 signaling (IIS). ACNs and gut metabolites have great application prospects as functional foods and drugs to delay aging and manage age-related diseases. Further investigation should focus on the interaction between ACNs and gut microbiota, including clarifying the complex metabolic pathway and maximizing the health effects of ACNs.

Lactobacillus, Bifidobacterium and Lactococcus response to environmental stress: Mechanisms and application of cross-protection to improve resistance against freeze-drying.

The review deals with lactic acid bacteria in characterizing the stress adaptation with cross-protection effects, mainly associated with Lactobacillus, Bifidobacterium and Lactococcus. It focuses on adaptation and cross-protection in Lactobacillus, Bifidobacterium and Lactococcus, including heat shocking, cold stress, acid stress, osmotic stress, starvation effect, etc. Web of Science, Google Scholar, Science Direct, and PubMed databases were used for the systematic search of literature up to the year 2020. The literature suggests that a lower survival rate during freeze-drying is linked to environmental stress. Protective pretreatment under various mild stresses can be applied to lactic acid bacteria which may enhance resistance in a strain-dependent manner. We investigate the mechanism of damage and adaptation under various stresses including heat, cold, acidic, osmotic, starvation, oxidative and bile stress. Adaptive mechanisms include synthesis of stress-induced proteins, adjusting the composition of cell membrane fatty acids, accumulating compatible substances, etc. Next, we reveal the cross-protective effect of specific stress on the other environmental stresses. Freeze-drying is discussed from three perspectives including the regulation of membrane, accumulation of compatible solutes and the production of chaperones and stress-responsive proteases. The resistance of lactic acid bacteria against technological stress can be enhanced via cross-protection, which improves industrial efficiency concerning the survival of probiotics. However, the adaptive responses and cross-protection are strain-dependent and should be optimized case by case.

The Effect of Proline on the Freeze-Drying Survival Rate of Bifidobacterium longum CCFM 1029 and Its Inherent Mechanism.

Amino acids, which are important compatible solutes, play a significant role in probiotic lyophilization. However, studies on the functions of Bifidobacterium during freeze-drying are limited. Therefore, in this study, we compared the freeze-drying survival rate of Bifidobacterium longum CCFM 1029 cultivated in different media containing different kinds of compatible solutes. We found that the addition of 21 g/L proline to the culture media substantially improved the freeze-drying survival rate of B. longum CCFM 1029 from 18.61 ± 0.42% to 38.74 ± 1.58%. Interestingly, this change has only been observed when the osmotic pressure of the external culture environment is increased. Under these conditions, we found that proline accumulation in this strain increased significantly. This change also helped the strain to maintain its membrane integrity and the activity of some key enzymes during freeze-drying. Overall, these results show that the addition of proline can help the strain resist a tough environment during lyophilization. The findings of this study provide preliminary data for producers of probiotics who wish to achieve higher freeze-drying survival rates during industrial production.

Postbiotics Prepared Using Lactobacillus paracasei CCFM1224 Prevent Nonalcoholic Fatty Liver Disease by Modulating the Gut Microbiota and Liver Metabolism.

Postbiotics are rich in a variety of bioactive components, which may have beneficial effects in inhibiting hepatic lipid accumulation. In this study, we investigated the preventive effects of postbiotics (POST) prepared from Lactobacillus paracasei on non-alcoholic fatty liver disease (NAFLD). Our results showed that when mice ingested a high-fat diet (HFD) and POST simultaneously, weight gain was slowed, epididymal white fat hypertrophy and insulin resistance were suppressed, serum biochemical indicators related to blood lipid metabolism were improved, and hepatic steatosis and liver inflammation decreased. Bacterial sequencing showed that POST modulated the gut microbiota in HFD mice, increasing the relative abundance of Akkermansia and reducing the relative abundance of Lachnospiraceae NK4A136 group, Ruminiclostridium and Bilophila. Spearman's correlation analysis revealed significant correlations between lipid metabolism parameters and gut microbes. Functional prediction results showed that the regulation of gut microbiota was associated with the improvement of metabolic status. The metabolomic analysis of the liver revealed that POST-regulated liver metabolic pathways, such as glycerophospholipid and ether lipid metabolism, pantothenate and CoA biosynthesis, some parts of amino acid metabolism, and other metabolic pathways. In addition, POST regulated the gene expression in hepatocytes at the mRNA level, thereby regulating lipid metabolism. These findings suggest that POST plays a protective role against NAFLD and may exert its efficacy by modulating the gut microbiota and liver metabolism, and these findings may be applied to related functional foods.

Bifidobacteria exhibited stronger ability to utilize fructooligosaccharides, compared with other bacteria in the mouse intestine.

BACKGROUND: Fructooligosaccharides (FOS) have been identified as important prebiotics. Previous studies have found that they can significantly promote the proliferation of Bifidobacterium pseudolongum in the mouse intestine. However, it is still unclear which other bacteria in the mouse intestine can utilize FOS, and the differences in the ability to utilize FOS. In this study, the bacteria capable of utilizing FOS were isolated from mice feces and their ability to utilize FOS was compared. Draft genome sequencing was also applied to explain the differences in FOS utilization at the gene levels. RESULTS: A total of 15 species were isolated from mouse feces and 13 species were able to utilize fructofuranosylnystose (GF2). Eleven species could utilize nistose (GF3), but not Enterococcus hirae and Lactobacillus reuteri. In contrast, 1-kestose (GF4) was hardly utilized. The enzyme activity determination and draft genome sequencing-based analyses revealed that all isolated species used the phosphotransferase system or permease system to transport FOS into the cells before hydrolysis by ß-fructofuranosidase. Although ß-fructofuranosidase exists in all strains, there are big differences in the corresponding coding genes between bifidobacteria and non-bifidobacteria. CONCLUSION: Compared with the other isolates, Bifidobacterium species exhibited higher enzyme activity and shorter generation time, leading to a stronger ability to utilize FOS. © 2021 Society of Chemical Industry.

Effects of fructooligosaccharides (FOS) on the composition of cecal and fecal microbiota and the quantitative detection of FOS-metabolizing bacteria using species-specific primers.

BACKGROUND: Fructooligosaccharides (FOS) are a kind of prebiotic. Previous studies concerning the effect of FOS on intestinal microbiota have focused on Bifidobacterium and Lactobacillus. However, the presence of other FOS-utilizing bacteria makes it necessary to investigate the quantitative changes in these bacterial species in the intestine after FOS intake. In this study, the composition of cecal and fecal microbiota was analyzed using MiSeq sequencing, and the abundance of FOS-utilizing bacteria was detected using quantitative polymerase chain reaction after the oral administration of FOS. RESULTS: Species-specific primers for FOS-utilizing bacteria were designed with superior amplification efficiency for quantification. After FOS intervention, the relative abundance of Bifidobacterium pseudolongum in feces increased to 17.37% and the abundance reached 2.28 × 1010 CFU g-1 . The abundance of Bifidobacterium longum and Bifidobacterium breve did not change significantly. Whereas the abundance of Ligilactobacillus murinus decreased, that of Lactiplantibacillus plantarum, Lacticaseibacillus paracasei, and Lacticaseibacillus rhamnosus remained at approximately 104 CFU g-1 . CONCLUSION: Species-specific primers for FOS-utilizing bacteria were successfully developed, and we confirmed that FOS significantly increased the relative abundance and the abundance of B. pseudolongum in mice, while decreasing the proportion of Lactobacillus. The detection of these species using 16S ribosomal DNA sequencing and quantitative polymerase chain reaction showed the same results. Further investigations are needed to reveal the response of the intestinal microbiota to different FOS compositions. These techniques will contribute to future studies about the composition and dynamics of the intestinal microflora. © 2022 Society of Chemical Industry.

Gas chromatography-mass spectrometry-based metabolomics analysis of metabolites in commercial and inoculated pickles.

BACKGROUND: Starter cultures are nowadays more and more used to make inoculated pickles (IPs), but it remains unclear whether there are differences in flavors between IPs and naturally fermented pickles. In this study 16 commercial pickles (CPs) produced by spontaneous fermentation method were purchased from markets in Sichuan province and Chongqing. Ten strains of three lactic acid bacteria species - Lactobacillus plantarum, Leuconostoc mesenteroides and Pediococcus ethanolidurans - were selected as single starter cultures to produce IPs. RESULTS: Differences in flavor components between the CPs and IPs were monitored using a combination of gas chromatography-mass spectrometry and multivariate statistical methods. Higher levels of nonvolatile substances such as glucose, fructose, tagatose, sucrose, lactic acid and mannitol were detected in most IPs than in the CPs. The values of flavor characteristics such as sweetness, umami and astringency, which were correlated positively with consumers' overall preferences for pickles, were higher in the IPs than in the CPs. Volatile compounds such as geranyl acetate, dimethyl trisulfide, eucalyptol and linalool were distinguished as the main compounds that contributed to the flavor characteristics of the CPs. In addition to dimethyl trisulfide, dimethyl disulfide was also an odor contributor to the IPs. CONCLUSIONS: The CPs and IPs had different flavor characteristics, especially in the composition and content of volatile components, and the inoculation method reflected some fermentation advantages, which could reduce the bitterness and increase umami and lead to a higher score of sensory preference. This will be helpful for industrial production. © 2020 Society of Chemical Industry.