Engineering of Aspergillus niger for efficient production of D-xylitol from L-arabinose.

D-Xylitol is a naturally occurring sugar alcohol present in diverse plants that is used as an alternative sweetener based on a sweetness similar to sucrose and several health benefits compared to conventional sugar. However, current industrial methods for D-xylitol production are based on chemical hydrogenation of D-xylose, which is energy-intensive and environmentally harmful. However, efficient conversion of L-arabinose as an additional highly abundant pentose in lignocellulosic materials holds great potential to broaden the range of applicable feedstocks. Both pentoses D-xylose and L-arabinose are converted to D-xylitol as a common metabolic intermediate in the native fungal pentose catabolism.To engineer a strain capable of accumulating D-xylitol from arabinan-rich agricultural residues, pentose catabolism was stopped in the ascomycete filamentous fungus Aspergillus niger at the stage of D-xylitol by knocking out three genes encoding enzymes involved in D-xylitol degradation (ΔxdhA, ΔsdhA, ΔxkiA). Additionally, to facilitate its secretion into the medium, an aquaglyceroporin from Saccharomyces cerevisiae was tested. In S. cerevisiae, Fps1 is known to passively transport glycerol and is regulated to convey osmotic stress tolerance but also exhibits the ability to transport other polyols such as D-xylitol. Thus, a constitutively open version of this transporter was introduced into A. niger, controlled by multiple promoters with varying expression strengths. The strain expressing the transporter under control of the PtvdA promoter in the background of the pentose catabolism-deficient triple knock-out yielded the most favorable outcome, producing up to 45% D-xylitol from L-arabinose in culture supernatants, while displaying minimal side effects during osmotic stress. Due to its additional ability to extract D-xylose and L-arabinose from lignocellulosic material via the production of highly active pectinases and hemicellulases, A. niger emerges as an ideal candidate cell factory for D-xylitol production from lignocellulosic biomasses rich in both pentoses.In summary, we are showing for the first time an efficient biosynthesis of D-xylitol from L-arabinose utilizing a filamentous ascomycete fungus. This broadens the potential resources to include also arabinan-rich agricultural waste streams like sugar beet pulp and could thus help to make alternative sweetener production more environmentally friendly and cost-effective.

Altered sterol composition mediates multiple tolerance of Kluyveromyces marxianus for xylitol production.

BACKGROUND: Currently, the synthesis of compounds based on microbial cell factories is rapidly advancing, yet it encounters several challenges. During the production process, engineered strains frequently encounter disturbances in the cultivation environment or the impact of their metabolites, such as high temperature, acid-base imbalances, hypertonicity, organic solvents, toxic byproducts, and mechanical damage. These stress factors can constrain the efficiency of microbial fermentation, resulting in slow cell growth, decreased production, significantly increased energy consumption, and other issues that severely limit the application of microbial cell factories. RESULTS: This study demonstrated that sterol engineering in Kluyveromyces marxianus, achieved by overexpressing or deleting the coding genes for the last five steps of ergosterol synthase (Erg2-Erg6), altered the composition and ratio of sterols in its cell membrane, and affected its multiple tolerance. The results suggest that the knockout of the Erg5 can enhance the thermotolerance of K. marxianus, while the overexpression of the Erg4 can improve its acid tolerance. Additionally, engineering strain overexpressed Erg6 improved its tolerance to elevated temperature, hypertonic, and acid. YZB453, obtained by overexpressing Erg6 in an engineering strain with high efficiency in synthesizing xylitol, produced 101.22 g/L xylitol at 45oC and 75.11 g/L xylitol at 46oC. Using corncob hydrolysate for simultaneous saccharification and fermentation (SSF) at 46oC that xylose released from corncob hydrolysate by saccharification with hemicellulase, YZB453 can produce 45.98 g/L of xylitol, saving 53.72% of the cost of hemicellulase compared to 42oC. CONCLUSIONS: This study elucidates the mechanism by which K. marxianus acquires resistance to various antifungal drugs, high temperatures, high osmolarity, acidity, and other stressors, through alterations in the composition and ratio of membrane sterols. By employing sterol engineering, the fermentation temperature of this unconventional thermotolerant K. marxianus was further elevated, ultimately providing an efficient platform for synthesizing high-value-added xylitol from biomass via the SSF process at temperatures exceeding 45 °C.

Co-substrate model development and validation on pure sugars and corncob hemicellulosic hydrolysate for xylitol production.

A co-substrate model of Candida tropicalis TISTR 5306 cultivated in 10 - 100 g/L xylose and 1 - 10 g/L glucose at the ratio of 10:1 was developed based in part on modified Monod equation. The kinetic parameters include substrate limitation as well as substrate and product inhibitions with inclusion of threshold values. A general good fitting with average RSStotal, R2, and MStotal values of 162, 0.979, and 10.8, respectively, was achieved between ten simulated profiles and experimental kinetics data. The implementation of developed model on xylitol production from non-detoxified corncob hemicellulosic hydrolysate resulted in relatively good agreement with RSStotal, R2, and MStotal values of 368, 0.988, and 24.5, respectively. The developed model can be applied to predict microbial behavior in batch xylitol production system using hemicellulosic hydrolysate over a xylose range of 10 - 100 g/L and provide useful information for subsequent design of fed-batch and continuous systems to achieve the efficient sustainable resource management of this agricultural and agro-industrial waste.

CRISPRi-mediated metabolic switch enables concurrent aerobic and synthetic anaerobic fermentations in engineered consortium.

Replacing petrochemicals with compounds from bio-based manufacturing processes remains an important part of the global effort to move towards a sustainable future. However, achieving economic viability requires both optimized cell factories and innovative processes. Here, we address this challenge by developing a fermentation platform, which enables two concurrent fermentations in one bioreactor. We first construct a xylitol producing Escherichia coli strain in which CRISPRi-mediated gene silencing is used to switch the metabolism from aerobic to anaerobic, even when the bacteria are under oxic conditions. The switch also decouples growth from production, which further increases the yield. The strain produces acetate as a byproduct, which is subsequently metabolized under oxic conditions by a secondary E. coli strain. Through constraint-based metabolic modelling this strain is designed to co-valorize glucose and the excreted acetate to a secondary product. This unique syntrophic consortium concept facilitates the implementation of "two fermentations in one go", where the concurrent fermentation displays similar titers and productivities as compared to two separate single strain fermentations.

Two-stage seeding strategy and its multi-response optimization for enhanced xylitol production by Debaryomyces nepalensis NCYC 3413.

The aim was to develop a two-stage seeding strategy and its optimization to enhance the conversion of xylose to xylitol by Debaryomyces nepalensis NCYC 3413. To develop efficient seed, multi-response optimization was employed to obtain optimal inoculum age and volume where xylitol concentration, yield and productivity were maximized. The optimal conditions of inoculation age and volume were 5.86 h and 11.66 % (v/v), respectively. Maximized results were observed at 48 h as compared to 72 h pre-optimization. Xylitol concentration slightly improved from 56 g/L to 59.71 g/L (p-value = 0.043). Yield improved from 0.56 g/g to 0.66 g/g (p-value = 0.044), whereas, productivity showed a significant increase from 0.76 g/L.h to 1.24 g/L.h (p-value = 0.008). Xylose Reductase activity improved by 1.67-folds and Xylitol Dehydrogenase activity decreased by 1.3 folds. This work suggests a simple inoculum strategy that could expedite the enzyme system required for xylitol production, enabling a 1.7-fold increase in productivity.

Effect of Xylitol on Inhibition and Eradication of Pseudomonas aeruginosa PAO1 and Methicillin-Resistant Staphylococcus aureus Biofilms in an Alginate Bead Model.

Biofilms formed by Pseudomonas aeruginosa and Staphylococcus aureus, along with their antibiotic tolerance have posed challenges to treatment strategies for lung, wound, and other infections, particularly when co-infecting. In the present study, the inhibitory effect of xylitol on biofilm formation, as well as its eradication potential on pre-established biofilms formed by P. aeruginosa strain PAO1, methicillin-resistant S. aureus, and a mix of both species in an alginate bead model were tested. Xylitol concentrations of 2, 1, and 0.5 M reduced biofilm formation by P. aeruginosa strain PAO1, methicillin-resistant S. aureus, and the mixed-species biofilm in a concentration-dependent manner. Additionally, biofilms formed by these species were subjected to treatment with xylitol. Xylitol was also capable of eradicating biofilms established by P. aeruginosa strain PAO1, methicillin-resistant S. aureus, and the mixed-species biofilm by at least 20%, with the most effective eradication observed for P. aeruginosa strain PAO1. The present study indicates the effectiveness of xylitol as both an inhibitory and eradicating agent against biofilms formed by P. aeruginosa strain PAO1, methicillin-resistant S. aureus, and a mix of both species in an alginate bead model, which mimics the in vivo characteristics of P. aeruginosa aggregates.

Xylitol is prothrombotic and associated with cardiovascular risk.

BACKGROUND AND AIMS: The pathways and metabolites that contribute to residual cardiovascular disease risks are unclear. Low-calorie sweeteners are widely used sugar substitutes in processed foods with presumed health benefits. Many low-calorie sweeteners are sugar alcohols that also are produced endogenously, albeit at levels over 1000-fold lower than observed following consumption as a sugar substitute. METHODS: Untargeted metabolomics studies were performed on overnight fasting plasma samples in a discovery cohort (n = 1157) of sequential stable subjects undergoing elective diagnostic cardiac evaluations; subsequent stable isotope dilution liquid chromatography tandem mass spectrometry (LC-MS/MS) analyses were performed on an independent, non-overlapping validation cohort (n = 2149). Complementary isolated human platelet, platelet-rich plasma, whole blood, and animal model studies examined the effect of xylitol on platelet responsiveness and thrombus formation in vivo. Finally, an intervention study was performed to assess the effects of xylitol consumption on platelet function in healthy volunteers (n = 10). RESULTS: In initial untargeted metabolomics studies (discovery cohort), circulating levels of a polyol tentatively assigned as xylitol were associated with incident (3-year) major adverse cardiovascular event (MACE) risk. Subsequent stable isotope dilution LC-MS/MS analyses (validation cohort) specific for xylitol (and not its structural isomers) confirmed its association with incident MACE risk [third vs. first tertile adjusted hazard ratio (95% confidence interval), 1.57 (1.12-2.21), P < .01]. Complementary mechanistic studies showed xylitol-enhanced multiple indices of platelet reactivity and in vivo thrombosis formation at levels observed in fasting plasma. In interventional studies, consumption of a xylitol-sweetened drink markedly raised plasma levels and enhanced multiple functional measures of platelet responsiveness in all subjects. CONCLUSIONS: Xylitol is associated with incident MACE risk. Moreover, xylitol both enhanced platelet reactivity and thrombosis potential in vivo. Further studies examining the cardiovascular safety of xylitol are warranted.

Non-antibiotic antimicrobial agents for chronic rhinosinusitis: a narrative review.

OBJECTIVE: This narrative review explores alternative non-antibiotic antimicrobial agents for CRS management in adults. METHODS: Alternative antimicrobial agents using EPOS 2020 guidelines as reference were selected, and articles dated from 2003 to 2022 in English, Portuguese, or Spanish using PubMed and EMBASE databases. The parameters analyzed included study design, evidence level, population characteristics, CRS characteristics, interventions, outcomes, sample size, randomization, blinding, and side effects. Reviews, unrelated contexts,in vitro experiments, and duplicates were excluded. RESULTS: 148 articles were screened; 19 articles were selected for analysis. Randomized controlled trials and cohort studies assessing non-antibiotic antimicrobial treatments for CRS were included. Xylitol demonstrated effectiveness in reducing CRS symptoms, particularly SNOT-22 scores, surpassing saline irrigation benefits. Manuka honey showed potential microbiological benefits in recalcitrant CRS, but symptomatic and endoscopic improvements remained inconclusive. Baby shampoo irrigation improved nasal mucociliary clearance and postoperative outcomes. Colloidal silver nasal irrigation showed limited efficacy in reducing CRS symptoms or endoscopic scores. Povidone-Iodine (PI) nasal irrigation yielded mixed results, with varying effects on culture negativity and SNOT-20 scores. Bacteriophage treatment exhibited promise in decreasing specific bacterial strains and cytokine levels. CONCLUSION: Non-antibiotic antimicrobial therapies, including xylitol, manuka honey, baby shampoo, colloidal silver, PI, bacteriophages, lactoferrin, and carrageenan offer potential alternatives for CRS in adult patients. Xylitol, baby shampoo, and PI presented benefits in improving symptoms and nasal endoscopic scores, however, the number of studies is limited for conclusive recommendations and safety assessments. CRS management should adopt a comprehensive approach, particularly for non-infectious or immune-related cases, moving beyond antibiotics. Antibiotics should be reserved for confirmed bacterial infections. Overall, this review shows the importance of exploring non-antibiotic therapies to enhance the management of CRS.

How xylitol, gluten, and lactose change human gut microbiota Escherichia coli and Lactobacillus rhamnosus GG biofilm.

OBJECTIVE: The human gut microbiota is composed of many viruses, bacteria, and fungi. Escherichia coli representatives are facultative anaerobic bacteria in the colon that play a crucial role in the metabolism of lactose, vitamin synthesis, and immune system modulation. E. coli forms a biofilm on the epithelial cell surface of the intestine that can be modified by diet compounds, i.e., gluten, xylitol, lactose, and probiotics. METHODS: In the present study, the impact of probiotic-derived Lactobacillus rhamnosus GG strain on non-pathogenic E. coli biofilm was examined. The mono- and multispecies biofilm was also treated with gluten, xylitol, and lactose. We used 96-well plates to obtain biofilm growth. Biofilm was stained using crystal violet. To evaluate the type of interaction in mono- and multispecies biofilm, a new formula was introduced: biofilm interaction ratio index (BIRI). To describe the impact of nutrients on biofilm formation, the biofilm formation impact ratio (BFIR) was calculated. RESULTS: The biofilms formed by both examined species are stronger than in monocultures. All the BIRI values were above 3.0. It was found that the monospecies biofilm of L. rhamnosus is strongly inhibited by gluten (84.5%) and the monospecies biofilm of E. coli by xylitol (85.5%). The mixed biofilm is inhibited by lactose (78.8%) and gluten (90.6%). CONCLUSION: The relations between bacteria in the mixed biofilm led to changes in biofilm formation by E. coli and L. rhamnosus GG. Probiotics might be helpful in rebuilding the gut microbiota after broad spectrum antibiotic therapy, but only if gluten and lactose are excluded from diet.

Sugar substitutes on caries prevention in permanent teeth among children and adolescents: a systematic review and meta-analysis.

OBJECTIVES: This study aimed to systematically review the effect of sugar substitute consumption on caries prevention in permanent teeth among children and adolescents. DATA: Randomized controlled trials (RCTs) and controlled clinical trials (CCTs) comparing the clinical effect of sugar substitutes (both high- and low-intensity sweeteners) in preventing caries in permanent teeth among children and adolescents aged 6-19 were included. SOURCES: A systematic search was conducted in three databases (PubMed, Web of Science and Embase) without any restrictions on publication year. STUDY SELECTION: The initial search found 1,859 items, and finally, 15 studies (11 RCTs and 4 CCTs) with a total of 6325 participants (age: 6-18 years) were included. The Cochrane risk-of-bias assessment tools were used for quality assessment. Most (80%, 12/15) were graded as having a 'moderate' or 'high' risk of bias. All trials investigated sugar alcohol, which is a low-intensity sweetener. Xylitol was the most commonly investigated (73.3%, 11/15), followed by sorbitol (46.7%, 7/15), and erythritol (13.3%, 2/15). Results of the meta-analysis showed that both xylitol (standardized mean difference [SMD]: -0.50, 95% confidence interval [CI] -0.85 to -0.16, P = 0.005) and sorbitol (SMD: -0.10, 95% CI: -0.19 to -0.01, P = 0.03) had a significant effect in preventing dental caries compared to no treatment/placebo. No clinical trials on high-intensity sweeteners such as aspartame and saccharin were found. CONCLUSION: The consumption of xylitol or sorbitol is potentially effective in preventing caries in permanent teeth among children and adolescents. No clinical evidence is available regarding the role of high-intensity sweeteners in caries prevention. CLINICAL SIGNIFICANCE: The use of xylitol or sorbitol as sugar substitutes has a beneficial effect in preventing dental caries among children and adolescents.

Do chewing gums and sweets containing xylitol prevent caries in children?

DATA SOURCES: Three electronic databases (Pubmed, Embase and the Cochrane Library) were searched in December 2022, and again for additional literature on 3-5th January 2023. Reference lists of relevant systematic reviews were hand searched for other eligible studies for inclusion. STUDY SELECTION: Randomised controlled clinical trials and controlled clinical trials conducted on children (aged ≤ 18 years), conducted between 1974-2022 and available in English, were eligible for inclusion. Studies were excluded if caries was not an outcome, the control group was not sufficient, they were lab-based studies or studies where xylitol delivery was not a sweet or chewing gum and where the xylitol product contained a component such as fluoride which may influence the outcomes. DATA EXTRACTION AND SYNTHESIS: Four calibrated reviewers independently screened titles and abstracts, and disagreements were resolved via group discussion. Preventative effect was determined by comparing the mean caries increment in the control and intervention groups, producing a preventative fraction. A total of 617 titles were initially screened for relevance. After duplicate removal, 268 abstracts were screened and 16 full text articles reviewed, with one more study then excluded. 10 studies investigated xylitol-containing chewing gum, and six looked at xylitol candy (one did both). Eight included studies were randomised controlled trials. Data extraction was undertaken by two reviewers. RESULTS: 3466 participants were included in the 10 studies that investigated xylitol chewing gum, and all 10 studies reported a statistically significant preventive effect compared to a no chewing gum or placebo control. In 9 studies, the preventive fraction was clinically significant. The six studies investigating xylitol candies contained a total of 1023 participants, and only one study demonstrated a significant preventative effect. CONCLUSIONS: There is some evidence that incorporating xylitol chewing gum daily has a caries-reducing effect in those with a moderate-to-high baseline caries level. This effect was not present for xylitol sweets.

Preparation of orodispersible tablets of bosentan using xylitol and menthol as dissolution enhancers.

Bosentan is a drug used to treat pulmonary hypertension via dual endothelial receptor antagonism. Bosentan has a restricted oral bioavailability, a problem that's mostly due to poor solubility and hepatic metabolism. It is extensively used for the elderly and children who require a friendly dosage form like orodispersible tablets. So, the goal of this research work was to hasten the dissolution rate of bosentan to produce an orodispersible tablet with immediate drug release. Bosentan was exposed to ethanol-assisted kneading with a rise of xylitol or menthol concentrations (1:1 and 1:2 molar ratio of bosentan with excipient). In addition to observing the dissolution behavior, the resulting dry products were investigated using Fourier transform infrared spectroscopy (FTIR), differential thermal analysis (DTA), and X-ray diffraction (XRD). The FTIR reflected possible hydrogen bonding with xylitol and menthol. DSC studies reflected a reduction in the enthalpy and Tm. These results with XRD data reflected partial co-amorphization in the case of xylitol and eutaxia in the case of menthol. These modifications were related to an accelerated dissolving rate. The developed systems were fabricated as orodispersible tablets which exhibited immediate release of bosentan. Thus, the current study offered simple co-processing for the preparation of orodispersible bosentan tablets.

Xylitol fermentation characteristics with a newly isolated yeast Wickerhamomyces anomalus WA.

Xylitol is an increasingly popular functional food additive, and the newly isolated yeast Wickerhamomyces anomalus WA has shown extensive substrate utilization capability, with the ability to grow on hexose (d-galactose, d-glucose, d-mannose, l-fructose, and d-sorbose) and pentose (d-xylose and l-arabinose) substrates, as well as high tolerance to xylose at concentrations of up to 300 g/L. Optimal xylitol fermentation conditions were achieved at 32 °C, 140 rpm, pH 5.0, and initial cell concentration OD600 of 2.0, with YP (yeast extract 10 g/L, peptone 20 g/L) as the optimal nitrogen source. Xylitol yield increased from 0.61 g/g to 0.91 g/g with an increase in initial substrate concentration from 20 g/L to 180 g/L. Additionally, 20 g/L glycerol was found to be the optimal co-substrate for xylitol fermentation, resulting in an increase in xylitol yield from 0.82 g/g to 0.94 g/g at 140 rpm, enabling complete conversion of xylose to xylitol.

Metabolic Effects of Selected Conventional and Alternative Sweeteners: A Narrative Review.

Sugar consumption is known to be associated with a whole range of adverse health effects, including overweight status and type II diabetes mellitus. In 2015, the World Health Organization issued a guideline recommending the reduction of sugar intake. In this context, alternative sweeteners have gained interest as sugar substitutes to achieve this goal without loss of the sweet taste. This review aims to provide an overview of the scientific literature and establish a reference tool for selected conventional sweeteners (sucrose, glucose, and fructose) and alternative sweeteners (sucralose, xylitol, erythritol, and D-allulose), specifically focusing on their important metabolic effects. The results show that alternative sweeteners constitute a diverse group, and each substance exhibits one or more metabolic effects. Therefore, no sweetener can be considered to be inert. Additionally, xylitol, erythritol, and D-allulose seem promising as alternative sweeteners due to favorable metabolic outcomes. These alternative sweeteners replicate the benefits of sugars (e.g., sweetness and gastrointestinal hormone release) while circumventing the detrimental effects of these substances on human health.

Comprehensive in vitro and in ovo assessment of cytotoxicity: Unraveling the impact of sodium fluoride, xylitol, and their synergistic associations in dental products.

Over the past several decades, dental health products containing fluoride have been widely employed to mitigate tooth decay and promote oral hygiene. However, concerns regarding the potential toxicological repercussions of fluoride exposure have incited continuous scientific inquiry. The current study investigated the cytotoxicity of sodium fluoride (NaF) and xylitol (Xyl), both individually and in combination, utilizing human keratinocyte (HaCaT) and osteosarcoma (SAOS-2) cell lines. In HaCaT cells, NaF decreased proliferation in a concentration-dependent manner and induced apoptosis-related morphological changes at low concentrations, whereas Xyl exhibited dose-dependent cytotoxic effects. The combination of NaF and Xyl reduced cell viability, particularly at higher concentrations, accompanied by apoptosis-like morphological alterations. Sub-cytotoxic NaF concentrations (0.2%) significantly affected caspase activity and the expression of pro-apoptotic genes. Conversely, Xyl demonstrated no discernible effect on these biological parameters. In SAOS-2 cells, NaF increased proliferation at high concentrations, contrasting with Xyl's concentration-dependent cytotoxic effects. The combination of NaF and Xyl had a minimal impact on cell viability. Sub-cytotoxic NaF concentrations did not influence caspase activity or gene expression, while Xyl induced dose-dependent morphological alterations, increased caspase activity, and upregulated pro-apoptotic gene expression. In ovo experiments on the chorioallantoic membrane (CAM) revealed that only NaF induced irritant effects, suggesting potential vascular adverse outcomes. This study advocates for the combined use of NaF and Xyl, highlighting their cytotoxicity benefits in healthy cells while maintaining safety considerations for tumor cells.

The effect of xylitol chewing gums and candies on caries occurrence in children: a systematic review with special reference to caries level at study baseline.

PURPOSE: A systematic review of published data was carried out to assess the caries-preventive effects of xylitol chewing gums and candies in children. METHODS: Electronic and hand searches were performed to find clinical studies on the effects of xylitol chewing gums and candies on dental caries in children (≤ 18 years). Prospective randomised or controlled clinical trials published before 2023 were included in the review. RESULTS: The initial search identified 365 titles to be evaluated. After applying inclusion and exclusion criteria, 15 articles with either fair or low quality were reviewed. Nine articles studied chewing gums, five candies, and one both of them. In the ten evaluated xylitol chewing gum studies xylitol consumption significantly reduced caries occurrence when compared with no treatment or a placebo polyol gum. The effect was clinically significant in studies with high or moderate caries level at study baseline. The results also suggested that the caries-reducing effect of xylitol gums may differ from sorbitol/polyol gums. In five of the six heterogenous xylitol candy studies, no caries-reducing effect was found independent of caries level. In addition to caries level, also the daily xylitol dose was a confounding factor. CONCLUSION: The present findings suggest that the caries-reducing effect of adding xylitol chewing gum to the daily diet has been well demonstrated in children and adolescents with high or moderate caries level at study baseline. Xylitol gum use could benefit subjects with active incipient caries lesions on smooth tooth surfaces.

The food additive xylitol enhances the butyrate formation by the child gut microbiota developed in a dynamic colonic simulator.

The gut microbiota should be included in the scientific processes of risk assessment of food additives. Xylitol is a sweetener that shows low digestibility and intestinal absorption, implying that a high proportion of consumed xylitol could reach the colonic microbiota. The present study has evaluated the dose-dependent effects of xylitol intake on the composition and the metabolic activity of the child gut-microbiota. The study was conducted in a dynamic simulator of the colonic microbiota (BFBL Gut Simulator) inoculated with a child pooled faecal sample and supplemented three times per day, for 7 days, with increasing xylitol concentrations (1 g/L, 3 g/L and 5 g/L). Sequencing of 16S rRNA gene amplicons and group-specific quantitative PCR indicated a xylitol dose-response effect on the abundance of Lachnospiraceae, particularly the genera Blautia, Anaerostipes and Roseburia. The microbial changes observed with xylitol corresponded with a dose-dependant effect on the butyrate concentration that, in parallel, favoured an increase in epithelial integrity of Caco-2 cells. The study represents a detailed observation of the bacterial taxa that are the main contributors to the metabolism of xylitol by the child gut microbiota and the results could be relevant in the risk assessment re-evaluation of xylitol as a sweetener.

Organic tracers in fine and coarse aerosols at an urban Mediterranean site: contribution of biomass burning and biogenic emissions.

The concentrations of anhydrosugars (levoglucosan, mannosan, and galactosan), polyols (inositol, xylitol, sorbitol, and mannitol), and glucose were measured in PM1 and PM10 samples collected during 1 year at a traffic site in the city of Elche (southeastern Spain). Levoglucosan, mannosan, and galactosan were mainly found in the PM1 fraction since they are mainly emitted from biomass burning (BB). Likewise, inositol, xylitol, and sorbitol were primarily distributed in the fine mode, suggesting a non-negligible contribution from anthropogenic sources (specifically BB) to the levels of these compounds. This was supported by their seasonal variations, with higher concentrations during winter, and their correlations with levoglucosan concentrations. The average contributions of biomass burning and biogenic sources to OC and PM levels were calculated using levoglucosan and mannitol, respectively, as tracers. On average, BB accounted for 12% and 16% of the OC in PM1 and PM10, while the estimated contribution of fungal spores to OC and PM10 levels was 1.2 and 0.8%, respectively. The results of the present study suggest that, at least in the study area, most sugar alcohols are not appropriate tracers of biogenic emissions.

Natural intestinal metabolite xylitol reduces BRD4 levels to mitigate renal fibrosis.

Renal fibrosis is a typical pathological change from chronic kidney disease (CKD) to end-stage renal failure, which presents significant challenges in prevention and treatment. The progression of renal fibrosis is closely associated with the "gut-kidney axis," therefore, although clinical intervention to modulate the "gut-kidney axis" imbalance associated with renal fibrosis brings hope for its treatment. In this study, we first identified the close relationship between renal fibrosis development and the intestinal microenvironment through fecal microtransplantation and non-absorbable antibiotics experiments. Then, we analyzed the specific connection between the intestinal microenvironment and renal fibrosis using microbiomics and metabolomics, screening for the differential intestinal metabolite. Potential metabolite action targets were initially identified through network simulation of molecular docking and further verified by molecular biology experiment. We used flow cytometry, TUNEL apoptosis staining, immunohistochemistry, and Western blotting to assess renal injury and fibrosis extent, exploring the potential role of gut microbial metabolite in renal fibrosis development. We discovered that CKD-triggered alterations in the intestinal microenvironment exacerbate renal injury and fibrosis. When metabolomic analysis was combined with experiments in vivo, we found that the differential metabolite xylitol delays renal injury and fibrosis development. We further validated this hypothesis at the cellular level. Mechanically, bromodomain-containing protein 4 (BRD4) protein exhibits strong binding with xylitol, and xylitol alleviates renal fibrosis by inhibiting BRD4 and its downstream transforming growth factor-ß (TGF-ß) pathway. In summary, our findings suggest that the natural intestinal metabolite xylitol mitigates renal fibrosis by inhibiting the BRD4-regulated TGF-ß pathway.