Ascorbic acid potentiates photodynamic inactivation mediated by octyl gallate and blue light for rapid eradication of planktonic bacteria and biofilms.

This study reported for the first time that Ascorbic acid (AA) could appreciably boost the efficiency of Octyl gallate (OG)-mediated photodynamic inactivation (PDI) on Escherichia coli and Staphylococcus aureus in planktonic and biofilm states. The combination of OG (0.075 mM) and AA (200 mM) with 420 nm blue light (212 mW/cm2) led to a >6 Log killing within only 5 min for E. coli and S. aureus and rapid eradication of biofilms. The mechanism of action appears to be the generation of highly toxic hydroxyl radicals (•OH) via photochemical pathways. OG was exposed to BL irradiation to generate various reactive oxygen radicals (ROS) and the addition of AA could transform singlet oxygen (1O2) into hydrogen peroxide (H2O2), which could further react with AA to generate enormous •OH. These ROS jeopardized bacteria and biofilms by nonspecifically attacking various biomacromolecules. Overall, this PDI strategy provides a powerful microbiological decontamination modality to guarantee safe food products.

A novel core-shell up-conversion nanoparticles immunochromatographic assay for the detection of deoxynivalenol in cereals.

Deoxynivalenol (DON) toxin is a type B group of trichothecene mycotoxins mainly originating from specific Fusarium fungi, seriously harming human and livestock health. Herein, a novel core-shell up-conversion nanoparticles immunochromatographic assay (CS-UCNPs-ICA) was developed for deoxynivalenol based on the competitive reaction principle. By exploiting the fluorescence intensity of the T and C lines of CS-UCNPs-ICA, the concentrations of DON were obtained sensitively and precisely under optimized conditions in 5 min with a detection limit of 0.1 ng/mL. The CS-UCNPs-ICA strips only specifically detect DON and its derivatives (3-Ac-DON and 15-Ac-DON), with no cross-reaction with other mycotoxins. The low CV values illustrated a modest intra- and inter-assay variation, confirming the superior precision of this method. In the spiked experiment, the mean recoveries of corn and wheat ranged from 94.74% to 100.90% and 96.21%-104.81%, respectively. Furthermore, the approach generated results that were in good agreement with data from HPLC and ELISA analyses of naturally contaminated feed and cereals, confirming that the significant advantages of proposed strips were their high practicality, rapidness, and simplicity. Therefore, the CS-UCNPs-ICA strips platform serves as a promising candidate for developing new approaches for rapid testing or high throughput screening from DON in food products.

Galacto-Oligosaccharides Alleviate LPS-Induced Immune Imbalance in Small Intestine through Regulating Gut Microbe Composition and Bile Acid Pool.

Recent evidence suggests that the protective effect of gut microbiota on intestinal inflammation can be achieved through a microbe-bile acids (BAs) mechanism. Galacto-oligosaccharides (GOS) are a kind of prebiotic that alter gut microbiota composition. To verify whether GOS has a protective effect on intestinal inflammation through a microbe-BAs mechanism, this research was performed in a lipopolysaccharide (LPS) porcine model with the presence or absence of GOS. GOS prevented LPS-induced production of pro-inflammatory cytokines, the decrease of bacterial bile salt hydrolase-containing bacteria abundance, and the decrease of chendoxycholic acid (CDCA) level in piglets. Additionally, CDCA decreased LPS-induced production of pro-inflammatory cytokines, induced the expression of the takeda G-protein receptor 5 (TGR5), and its downstream cyclic adenosine monophosphate (cAMP) production in lamina propria-derived CD11b+ cells. The cAMP inhibitor eliminated the protective effect of CDCA on lamina propria-derived CD11b+ cells. These results suggested that GOS reduced the production of pro-inflammatory cytokines and inhibited NF-κB activation via microbe-BA-dependent TGR5-cAMP signaling in LPS-challenged piglets.

Synergistic effect of electrolyzed water generated by sodium chloride combined with dimethyl dicarbonate for inactivation of Listeria monocytogenes on lettuce.

BACKGROUND: Electrolyzed water (EW) is recognized as an effective way to control and reduce pathogens in vegetables. However, the disinfection efficacy of EW alone is limited. In this work, the bactericidal activity and biofilm removal capability of EW, generated by adding NaCl to a portable EW generator, were investigated with special reference to Listeria monocytogenes. Furthermore, the impact of EW in combination with dimethyl dicarbonate (DMDC) in reducing the microbial load and improving the overall quality of lettuce during refrigerated storage was evaluated. RESULTS: EW with 0.3% NaCl (SEW) had the highest bactericidal activity against L. monocytogenes. The pathogen treated with SEW exhibited lower superoxide dismutase activity and more leakage of proteins and nucleic acids than in the case of EW. Furthermore, the use of SEW resulted in changes in the cell permeability and morphology of L. monocytogenes. A decrease in adhesion and collapse of the biofilm architecture were also observed, indicating that SEW was more effective for inactivating L. monocytogenes cells compared to EW. For untreated lettuce, the populations of the total plate count and inoculated L. monocytogenes decreased by 2.47 and 2.35 log CFU g-1 , respectively, after the combined SEW/DMDC treatment for 3 min. The use of SEW alone or combined with DMDC did not negatively impact the lettuce color values, titratable acid, ascorbic acid and soluble solids compared to the control group. CONCLUSION: SEW in combination with DMDC can be used as a novel and potentially effective disinfection strategy for ensuring the safety of vegetable consumption. © 2023 Society of Chemical Industry.

Type II taste cells participate in mucosal immune surveillance.

The oral microbiome is second only to its intestinal counterpart in diversity and abundance, but its effects on taste cells remains largely unexplored. Using single-cell RNASeq, we found that mouse taste cells, in particular, sweet and umami receptor cells that express taste 1 receptor member 3 (Tas1r3), have a gene expression signature reminiscent of Microfold (M) cells, a central player in immune surveillance in the mucosa-associated lymphoid tissue (MALT) such as those in the Peyer's patch and tonsils. Administration of tumor necrosis factor ligand superfamily member 11 (TNFSF11; also known as RANKL), a growth factor required for differentiation of M cells, dramatically increased M cell proliferation and marker gene expression in the taste papillae and in cultured taste organoids from wild-type (WT) mice. Taste papillae and organoids from knockout mice lacking Spib (SpibKO), a RANKL-regulated transcription factor required for M cell development and regeneration on the other hand, failed to respond to RANKL. Taste papillae from SpibKO mice also showed reduced expression of NF-κB signaling pathway components and proinflammatory cytokines and attracted fewer immune cells. However, lipopolysaccharide-induced expression of cytokines was strongly up-regulated in SpibKO mice compared to their WT counterparts. Like M cells, taste cells from WT but not SpibKO mice readily took up fluorescently labeled microbeads, a proxy for microbial transcytosis. The proportion of taste cell subtypes are unaltered in SpibKO mice; however, they displayed increased attraction to sweet and umami taste stimuli. We propose that taste cells are involved in immune surveillance and may tune their taste responses to microbial signaling and infection.

Electronic tongue and electronic nose for food quality and safety.

For the needs of food producers and consumers, electronic tongue and electronic nose play many roles for food quality and safety in food production, food supervision and daily life. The principles and progresses of electronic tongue and electronic nose were elaborated. The core hardware namely electronic tongue sensors and electronic nose sensors, and the core software namely intelligent sensory algorithms were summarized. It was found that the proportion of electronic tongue and electronic nose employed in food quality control and monitoring in production was the highest. Electronic tongue and electronic nose with the prediction accuracy of 80-96 % accounted for a large proportion in the applications of food. The superposition operation of two or more intelligent sensory algorithms has become routine. In addition, the combination of electronic tongue and electronic nose was highlighted. It was resulted that the ability of food category recognition and quality prediction of the combined technology of electronic nose and electronic tongue showed an increase of 8-25 % compared with the single technology. The future challenges and expectations of electronic tongue and electronic nose were discussed.

Sensory sweetness and sourness interactive response of sucrose-citric acid mixture based on synergy and antagonism.

The clarity of taste sensation interaction is a key basis for promoting the food sensory science research and its application to the beverage and food additive industries. This study explored the synergy and antagonism effect of sucrose-citric acid mixture and established an optimized method to determine the human sweetness and sourness interactive response. Sucrose-citric acid mixtures were evaluated by the "close type" question. According to the sensory difference strength curves and Weber-Fechner law, citric acid increased the sucrose's absolute threshold (0.424-0.624%) and weber fraction (20.5-33.0%). Meanwhile, sucrose increased citric acid's absolute threshold (0.0057-0.0082%) and decreased its weber fraction (17.96-9.53%). By fitting absolute threshold and weber fraction variation equations, the sweet-sour taste sensory strength variation models (SSTVM) were derived, which could be used to explain the synergy and antagonism effect of sweet-sour taste. According to the SSTVM, the interactive response to sweet-sour taste could be quantitatively calculated. The high coincidence between SSTVM and human evaluation (1.02% of relative error) indicated that it could be applied in the food industry, health management, and intelligent sensory science.

Early-life galacto-oligosaccharides supplementation alleviates the small intestinal oxidative stress and dysfunction of lipopolysaccharide-challenged suckling piglets.

BACKGROUND: Galacto-oligosaccharides (GOS) are non-digestible food ingredients that promote the growth of beneficial bacteria in the gut. This study investigated the protective effect of the early-life GOS supplement on the piglets' gut function against the oxidative stress induced by lipopolysaccharide (LPS)-challenge. METHODS: Eighteen neonatal piglets were assigned to three groups including CON, LPS and LPS + GOS groups. The piglets in CON group and LPS group received physiological saline, while those in LPS + GOS group received GOS solution for 13 d after birth. On d 14, the piglets in LPS group and LPS + GOS group were injected with LPS solutions, while the piglets in CON group were injected with the same volume of physiological saline. RESULTS: The results showed that the early-life GOS supplement blocked the LPS-induced reactive oxygen species (ROS) secretion, malondialdehyde (MDA) production and the increase of pro-apoptotic factor expression. Meanwhile, the early-life GOS supplement improved the activities of antioxidant enzymes, disaccharidase enzymes activities, and digestive enzymes activities, and increased the mRNA abundance of the gene related to nutrient digestion and absorption and the relative protein expression of tight junction. The study also showed that the early-life GOS supplement improved the expression of Hemeoxygenase-1 (HO-1) and NAD(P)H/quinone acceptor oxidoreductase-1 (NQO-1), and activated the AMP-activated protein kinase (AMPK). CONCLUSIONS: These results suggested that GOS enhanced the gut function, reduced the ROS production and pro-apoptotic factors gene expression, and activated the AMPK signaling pathway in LPS-challenged piglets.

Effects of Protein Restriction and Succedent Realimentation on Jejunal Function and Bacterial Composition of Different Colonic Niches in Weaned Piglets.

Recent studies have proved that protein succedent realimentation could rescue the loss of growth performance in weaning piglets caused by a prior protein restriction. However, how the protein restriction and succedent realimentation influence the jejunal function and bacterial composition of different colonic niches microbiota in weaning piglets needs a further investigation. After protein succedent realimentation, we found that the treatment group (TRE) piglets had a higher IGF-1 content and IGF-1R gene expression level in jejunal mucosa than the control group (CON) piglets. The ZO-1 gene expression level was up-regulated in the jejunal mucosa of TRE piglets during protein restriction and succedent realimentation, while the jejunal permeability of TRE piglets was only decreased after protein succedent realimentation. In addition, we found that protein restriction and succedent realimentation increased the gene expression of Pept-1 and the fecal apparent digestibility of crude protein in TRE piglets, but decreased the fecal nitrogen content. After 16S rRNA MiSeq sequencing of bacteria in different colonic niches (mucosa and digesta), TRE piglets had a higher relative abundance of beneficial bacteria and a lower relative abundance of potential pathogens than CON piglets in different colonic niches after protein restriction and succedent realimentation. Our data showed that protein restriction and succedent realimentation decreased the concentrations of branch chain fatty acids and ammonia-N in the colon of TRE piglets. In addition, protein succedent realimentation increased the concentration of total short chain fatty acids in the colon of TRE piglets. All these findings demonstrated that the strategy of protein restriction and succedent realimentation is an effective way to improve intestinal health of weaning piglets, and provided new insights into the nutrition management of piglets during the weaning period.

Preparation of zein-lecithin-EGCG complex nanoparticles stabilized peppermint oil emulsions: Physicochemical properties, stability and intelligent sensory analysis.

Peppermint oil emulsions were prepared by using zein-lecithin-EGCG (Z-L/E) complex nanoparticles as emulsifiers. The preparation conditions of emulsions were optimized via measuring the particle size, surface tension and stability of emulsions, and peppermint oil of 3% (particle size = 375 nm, polydispersity index (PDI) = 0.45), the zein:lecithin ratio of 4:1 (w/w) (particle size = 396 nm), and the zein:EGCG ratio of 10:1 (w/w) (surface tension = 47.32 N/m) was the optimal condition. The rapid stability analysis showed that the instability mechanism of emulsions was ascribed to creaming and stratification, and the stability mechanism of emulsions was explored, indicating that the complex nanoparticles adsorbed on the surface of oil droplets to give Pickering emulsions. Electronic tongue experiments showed that the Z-E/L4:1 stabilized emulsion was distinguished from the other three samples due to its good stability. The electronic nose experiment could distinguish the emulsions with different droplet sizes.

Enhanced antibacterial efficacy and mechanism of octyl gallate/beta-cyclodextrins against Pseudomonas fluorescens and Vibrio parahaemolyticus and incorporated electrospun nanofibers for Chinese giant salamander fillets preservation.

A series of alkyl gallates were evaluated for the antibacterial activity against two common Gram-negative foodborne bacteria (Pseudomonas fluorescens and Vibrio parahaemolyticus) associated with seafood. The length of the alkyl chain plays a pivotal role in eliciting their antibacterial activities and octyl gallate (OG) exerted an excellent inhibitory efficacy. To extend the aqueous solubility, stability, and bactericidal properties of octyl gallate (OG), an inclusion complex between OG and ß-cyclodextrin (ßCD), OG/ßCD, was prepared and identified with various methods including X-ray diffraction (XRD), differential scanning calorimeter (DSC) and Fourier transform infrared spectroscopy (FTIR). Furthermore, the enhanced inhibitory effect and potential antibacterial mechanism of OG/ßCD against two Gram-negative and Gram-positive foodborne bacteria were comprehensively investigated. The results show that OG/ßCD could function against bacteria through effectively damaging the membrane, permeating into cells, and then disturbing the activity of the respiratory electron transport chain to cause the production of high-level intracellular hydroxyl radicals. Moreover, the reinforced OG/ßCD-incorporated polylactic acid (PLA) nanofibers were fabricated using the electrospinning technique as food packaging to extend the Chinese giant salamander fillet's shelf life at 4 °C. This research highlights the antibacterial effectiveness of OG/ßCD in aqueous media, which can be used as a safe multi-functionalized food additive combined with the benefits of electrospun nanofibers to extend the Chinese giant salamander fillets shelf life by 15 d at 4 °C.

Differential Effects of Early-Life and Postweaning Galacto-oligosaccharide Intervention on Colonic Bacterial Composition and Function in Weaning Piglets.

Recently, we proved that the early-life galacto-oligosaccharides (GOS) intervention could improve the colonic function by altering the bacterial composition in suckling piglets. However, whether the early-life GOS (ELG) intervention could have a long influence on the colonic microbiota and whether the combined ELG and postweaning GOS (PWG) intervention would have an interacting effect on maintaining colonic health in weaning piglets remain to be explored. In this study, we illustrated the differential effects of the ELG and PWG interventions on colonic microbiota and colonic function of weaning piglets. Our results showed that the ELG and PWG interventions decreased the frequency of diarrhea in weaning piglets while the PWG intervention increased colonic indexes. After 16S rRNA gene MiSeq sequencing of the gut bacteria belonging to different colonic niches (mucosa and digesta), the increase in the α-diversity of the colonic mucosal bacteria during PWG intervention was revealed. In addition, we found that both the ELG and PWG interventions enriched the relative abundances of short-chain fatty acid (SCFA) producers in different colonic niches and increased the total SCFA concentration in colonic digesta. These changes selectively modulated the mRNA expression levels of pattern recognition receptors and barrier proteins in the colonic mucosa. Of note, the combined effect of ELG and PWG effectively enhanced colonic SCFA producer enrichment and upregulated the butyrate concentration. Meanwhile, the expression levels of MyD88-NF-κB signaling and the proinflammatory cytokines were markedly reduced under the combined effect of ELG and PWG. IMPORTANCE Reducing the disorders of the gut ecosystem is an effective way to relieve weaning stresses of piglets and minimize economic losses in the modern swine industry. To this end, prebiotics have been often added to their diet during the weaning transition. In the present study, we demonstrated that the ELG and PWG interventions showed different effects on the bacterial composition of different colonic niches and on colonic function in the weaning piglets. Especially under the combined effect of ELG and PWG intervention, the expression levels of MyD88-NF-κB and the proinflammatory cytokines decreased with increasing concentrations of butyrate, which is an important microbial metabolite involved in the colon of weaning piglets. These findings further provided new insights into nutritional interventions that alleviate intestinal ecosystem dysbiosis and gut dysfunction in the piglets during the weaning transition.

Geographical origin determination of Red Huajiao in China using the electronic nose combined with ensemble recognition algorithm.

Red Huajiao was the most important Zanthoxylum species in China, and its quality was highly determined the geographical region. This study was aimed to establish a determination method for the geographical origin recognition of Red Huajiao by using the electronic nose and ensemble recognition algorithm. Six origins of samples were detected by the electronic nose, and two categories of electronic nose sensors characteristic values, named as "optimized characteristic value" and "filtered characteristic value," were obtained by the principal component analysis and discrimination index method and Filter-Wrapper method. Based on the two categories of characteristic values, 22 kinds of model analysis methods, which belonged to five categories of ensemble recognition algorithms were used to recognize the geographical origin. The total recognition accuracy rate of the two categories of characteristic values were 83.9% and 85.7%, respectively. Furthermore, during 22 kinds of model analysis method, the ensemble Subspace KNN and Bagged Trees methods in Ensemble Learning algorithm exhibited the best distinguishing ability with the accuracy rate more than 90%. Therefore, the electronic nose combined with Ensemble Learning would be promising for the geographical origin determination application. PRACTICAL APPLICATION: This work demonstrates that the Red Huajiao can be simply and rapidly determined by using electronic nose combined with ensemble recognition algorithm, allowing to effectively distinguish geographical origin of Red Huajiao, which can provide an important reference for the quality assessment of Huajiao.

Effect of Freeze-Thaw Cycles on Juice Properties, Volatile Compounds and Hot-Air Drying Kinetics of Blueberry.

This paper studied the effects of freeze-thaw (FT) cycles on the juice properties and aroma profiles, and the hot-air drying kinetics of frozen blueberry. After FT treatment, the juice yield increased while pH and total soluble solids of the juice keep unchanged. The total anthocyanins contents and DPPH antioxidant activities of the juice decreased by FT treatments. The electronic nose shows that FT treatments significantly change the aroma profiles of the juice. The four main volatile substances in the fresh juice are (E)-2-hexenal, α-terpineol, hexanal and linalyl formate, which account for 48.5 ± 0.1%, 17.6 ± 0.2%, 14.0 ± 1.5% and 7.8 ± 2.7% of relative proportions based on total ion chromatogram (TIC) peak areas. In the FT-treated samples, the amount of (E)-2-hexenal and hexanal decreased significantly while α-terpineol and linalyl formate remained almost unchanged. Repeated FT cycles increased the ethanol content and destroyed the original green leafy flavor. Finally, the drying kinetics of FT-treated blueberries was tested. One FT treatment can shorten the drying time by about 30% to achieve the same water content. The Deff values of the FT-treated sample are similar, which are about twice as large as the value of the fresh sample. The results will be beneficial for the processing of frozen blueberry into juice or dried fruits.

Fabrication and characterization of oil-in-water pickering emulsions stabilized by ZEIN-HTCC nanoparticles as a composite layer.

In this work, the ZEIN-HTCC nanoparticles formed by zein and N-(2-hydroxy)propyl-3-trimethylammonium chitosan chloride (HTCC) were used as stabilizers to prepare oil-in-water (O/W) Pickering emulsions. The preparation conditions including shearing time, volume fraction of corn oil, mass ratio of ZEIN:HTCC and total concentration of ZEIN-HTCC of emulsions were optimized by measuring the droplet size, zeta potential, PDI and surface tension of emulsions. The ZEIN-HTCC emulsions are stable at the pH range of 4-9 and in the low salt ion concentrations up to 0.2 mol L-1, and can keep stable up to 21 d during low temperature storage. Fourier transform infrared spectroscopy (FTIR), the confocal laser scanning microscope (CLSM) and scanning electron microscopy (SEM) were used to analyze the interaction between emulsion components, revealing that zein and HTCC form a composite layer by flocculation to adsorb on the surface of oil droplets, thus preventing emulsion droplets from aggregation. This novel, long-term stable, surfactant-free, and edible zein-based Pickering emulsion could be used as potential carriers for lipophilic nutrients delivery.

Galacto-oligosaccharides improve barrier function and relieve colonic inflammation via modulating mucosa-associated microbiota composition in lipopolysaccharides-challenged piglets.

BACKGROUND: Galacto-oligosaccharides (GOS) have been shown to modulate the intestinal microbiota of suckling piglets to exert beneficial effects on intestinal function. However, the modulation of intestinal microbiota and intestinal function by GOS in intestinal inflammation injury models has rarely been reported. In this study, we investigated the effects of GOS on the colonic mucosal microbiota composition, barrier function and inflammatory response of lipopolysaccharides (LPS)-challenged suckling piglets. METHODS: A total of 18 newborn suckling piglets were divided into three groups, the CON group, the LPS-CON group and the LPS-GOS group. Piglets in the LPS-GOS group were orally fed with 1 g/kg body weight of GOS solution every day. On the d 14, piglets in the LPS-CON and LPS-GOS group were challenged intraperitoneally with LPS solution. All piglets were slaughtered 2 h after intraperitoneal injection and sampled. RESULTS: We found that the colonic mucosa of LPS-challenged piglets was significantly injured and shedding, while the colonic mucosa of the LPS-GOS group piglets maintained its structure. Moreover, GOS significantly reduced the concentration of malondialdehyde (MDA) and the activity of reactive oxygen species (ROS) in the LPS-challenged suckling piglets, and significantly increased the activity of total antioxidant capacity (T-AOC). GOS significantly increased the relative abundance of norank_f__Muribaculaceae and Romboutsia, and significantly decreased the relative abundance of Alloprevotella, Campylobacter and Helicobacter in the colonic mucosa of LPS-challenged suckling piglets. In addition, GOS increased the concentrations of acetate, butyrate and total short chain fatty acids (SCFAs) in the colonic digesta of LPS-challenged suckling piglets. GOS significantly reduced the concentrations of interleukin 1ß (IL-1ß), interleukin 6 (IL-6), tumor necrosis factor-α (TNF-α) and cluster of differentiation 14 (CD14), and the relative mRNA expression of Toll-like receptor 4 (TLR4) and myeloid differentiation primary response 88 (MyD88) in the LPS-challenged suckling piglets. In addition, GOS significantly reduced the relative mRNA expression of mucin2 (MUC2), and significantly increased the protein expression of Claudin-1 and zonula occluden-1 (ZO-1) in LPS-challenged suckling piglets. CONCLUSIONS: These results suggested that GOS can modulate the colonic mucosa-associated microbiota composition and improve the intestinal function of LPS-challenged suckling piglets.

An optimized organic acid human sensory sourness analysis method.

BACKGROUND: Sour taste perception builds on both chemical and physiological foundations, and plays an important role in food flavor, including that of fruit, beer, wine, and other beverages. A uniform sourness standard and sourness conversion method for researchers and food enterprises is necessary to obtain uniform conclusions. RESULTS: This study established an optimized organic acid sensory sourness analysis and sourness conversion method. It is based on sour sensory difference strength curves, which consist of an absolute threshold value and sensory difference threshold values. Defining the absolute threshold value of citric acid sourness as 1, sourness could be calculated according to the curve. With a logarithmic curve form, the acid sourness indexes (AI) were calculated as 1, 0.74, 0.77, 1.31, and 1.21 for citric, malic, fumaric, lactic, and tartaric acid samples, respectively. Consequently, each acid's sourness and concentration could be obtained and converted. Single acid and mixed acid sourness comparison evaluation's result implied that the novel method was more accurate (91.7-100%) than the hydrogen ion concentration method. CONCLUSION: The novel sourness determination and conversion equation would provide more accurate sourness standard and calculation method in food sensory areas. © 2021 Society of Chemical Industry.

Xylitol enhances synthesis of propionate in the colon via cross-feeding of gut microbiota.

BACKGROUND: Xylitol, a white or transparent polyol or sugar alcohol, is digestible by colonic microorganisms and promotes the proliferation of beneficial bacteria and the production of short-chain fatty acids (SCFAs), but the mechanism underlying these effects remains unknown. We studied mice fed with 0%, 2% (2.17 g/kg/day), or 5% (5.42 g/kg/day) (weight/weight) xylitol in their chow for 3 months. In addition to the in vivo digestion experiments in mice, 3% (weight/volume) (0.27 g/kg/day for a human being) xylitol was added to a colon simulation system (CDMN) for 7 days. We performed 16S rRNA sequencing, beneficial metabolism biomarker quantification, metabolome, and metatranscriptome analyses to investigate the prebiotic mechanism of xylitol. The representative bacteria related to xylitol digestion were selected for single cultivation and co-culture of two and three bacteria to explore the microbial digestion and utilization of xylitol in media with glucose, xylitol, mixed carbon sources, or no-carbon sources. Besides, the mechanisms underlying the shift in the microbial composition and SCFAs were explored in molecular contexts. RESULTS: In both in vivo and in vitro experiments, we found that xylitol did not significantly influence the structure of the gut microbiome. However, it increased all SCFAs, especially propionate in the lumen and butyrate in the mucosa, with a shift in its corresponding bacteria in vitro. Cross-feeding, a relationship in which one organism consumes metabolites excreted by the other, was observed among Lactobacillus reuteri, Bacteroides fragilis, and Escherichia coli in the utilization of xylitol. At the molecular level, we revealed that xylitol dehydrogenase (EC 1.1.1.14), xylulokinase (EC 2.7.1.17), and xylulose phosphate isomerase (EC 5.1.3.1) were key enzymes in xylitol metabolism and were present in Bacteroides and Lachnospiraceae. Therefore, they are considered keystone bacteria in xylitol digestion. Also, xylitol affected the metabolic pathway of propionate, significantly promoting the transcription of phosphate acetyltransferase (EC 2.3.1.8) in Bifidobacterium and increasing the production of propionate. CONCLUSIONS: Our results revealed that those key enzymes for xylitol digestion from different bacteria can together support the growth of micro-ecology, but they also enhanced the concentration of propionate, which lowered pH to restrict relative amounts of Escherichia and Staphylococcus. Based on the cross-feeding and competition among those bacteria, xylitol can dynamically balance proportions of the gut microbiome to promote enzymes related to xylitol metabolism and SCFAs. Video Abstract.

The Clustered Regularly Interspaced Short Palindromic Repeats-Associated System and Its Relationship With Mobile Genetic Elements in Klebsiella.

Microorganisms have developed many strategies in the process of long-term defense against external attacks, one of which is the clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated proteins (Cas) bacterial immunological system. In this study, the whole genome of 300 strains of Klebsiella was collected, the CRISPR-Cas system in the strains was statistically analyzed, and the types and structures of CRISPR system in Klebsiella were explored, as well as the correlation between CRISPR and mobile genetic elements (MGEs). Through principal component analysis (PCA), we found that Cas gene, plasmids, integron, IS1, IS609, and enzymes of DNA metabolism were closely related to CRISPR-Cas. Compared the structural characteristics of plasmids, the DinG family helicases, Cas6, Csf2, and IS5 were observed near the CRISPR loci in plasmid, which is also confirmed by the results of PCA that they may be important factors affecting the plasmid with CRISPR.

Chitosan-chelated zinc modulates cecal microbiota and attenuates inflammatory response in weaned rats challenged with Escherichia coli.

Escherichia coli (E. coli) infection is very common among young growing animals, and zinc supplementation is often used to alleviate inflammation induced by this disease. Therefore, the objective of this study was to evaluate whether chitosan-chelated zinc (CS-Zn) supplementation could attenuate gut injury induced by E. coli challenge and to explore how CS-Zn modulates cecal microbiota and alleviates intestinal inflammation in weaned rats challenged with E. coli. 36 weaned rats (55.65 ± 2.18 g of BW, n = 12) were divided into three treatment groups consisting of unchallenged rats fed a basal diet (Control) and two groups of rats challenged with E. coli and fed a basal diet or a diet containing 640 mg/kg CS-Zn (E. coli + CS-Zn, containing 50 mg/kg Zn) for a 14-day experiment. On days 10 to 12, each rat was given 4 ml of E. coli solution with a total bacteria count of 1010 CFU by oral gavage daily or normal saline of equal dosage. CS-Zn supplementation mitigated intestinal morphology impairment (e.g. higher crypt depth and lower macroscopic damage index) induced by E. coli challenge (P < 0.05), and alleviated the increase of Myeloperoxidase (MPO) activity after E. coli challenge (P < 0.05). 16S rRNA sequencing analyses revealed that E. coli challenge significantly increased the abundance of Verrucomicrobia and E. coli (P < 0.05). However, CS-Zn supplementation increased the abundance of Lactobacillus and decreased the relative abundance of Proteobacteria, Desulfovibrio and E. coli (P < 0.05). The concentrations of butyrate in the cecal digesta, which decreased due to the challenge, were higher in the E. coli + CS-Zn group (P < 0.05). In addition, CS-Zn supplementation significantly prevented the elevation of pro-inflammatory cytokines IL-6 concentration and up-regulated the level of anti-inflammatory cytokines IL-10 in cecal mucosa induced by E. coli infection (P < 0.05). In conclusion, these results indicate that CS-Zn produces beneficial effects in alleviating gut mucosal injury of E. coli challenged rats by enhancing the intestinal morphology and modulating cecal bacterial composition, as well as attenuating inflammatory response.