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.

Characterization of a symbiotic beverage based on water-soluble soybean extract fermented by Lactiplantibacillus plantarum ATCC 8014

The health benefits of functional foods are associated with consumer interest and have supported the growth of the market for these types of foods, with emphasis on the development of new formulations based on plant extracts. Therefore, the present study aimed to characterize a symbiotic preparation based on water-soluble soy extract, supplemented with inulin and xylitol and fermented by Lactiplantibacillus plantarum ATCC 8014. Regarding nutritional issues, the symbiotic formulation can be considered a source of fiber (2 g/100 mL) and proteins (2.6 g/100 mL), and it also has a low-fat content and low caloric value. This formulation, in terms of microbiological aspects, remained adequate to legal standards after storage for 60 days under refrigeration and also presented an adequate quantity of the aforementioned probiotic strain, corresponding to 9.11 Log CFU.mL-1. These viable L. plantarum cells proved to be resistant to simulated human gastrointestinal tract conditions, reaching the intestine at high cell concentrations of 7.95 Log CFU.mL-1 after 60 days of refrigeration. Regarding sensory evaluation, the formulation showed good acceptance, presenting an average overall impression score of 6.98, 5.98, and 5.16, for control samples stored for 30 and 60 days under refrigeration, respectively. These results demonstrate that water-soluble soy extract is a suitable matrix for fermentation involving L. plantarum ATCC 8014, supporting and providing data on the first steps towards the development of a symbiotic functional food, targeting consumers who have restrictions regarding the consumption of products of animal origin, diabetics, and individuals under calorie restrictions.

Clinical Effects of Sugar Substitutes on Cariogenic Bacteria: A Systematic Review and Meta-Analysis

BACKGROUND

The use of sugar substitutes in food products has recently increased. Limited information regarding the role of various sugar substitutes in caries prevention was found. This systematic review and meta-analysis was conducted to investigate the effects of sugar substitute consumption on reducing cariogenic bacteria in dental plaque and saliva.

METHODS

We systematically searched PubMed, EMBASE, and Web of Science (inception to July 2023) for prospective controlled trials published in English and investigated the effects of sugar substitute consumption on cariogenic bacteria in dental plaque and saliva. The primary outcome was the changes in cariogenic bacteria. Two independent reviewers screened the papers. Quality was assessed using the Cochrane risk-of-bias tools.

RESULTS

From 977 studies identified, 32 trials were included. Almost half (14/32, 44%) of the included studies had a high risk of bias. Almost all (31/32, 96.88%) were investigations of xylitol and other sugar alcohols (low-intensity sweeteners), such as sorbitol, erythritol, and maltitol. Only one trial investigated stevia, a high-intensity sweetener, whereas no studies on other high-intensity sweeteners, such as sucralose, saccharin, or aspartame, were found. Almost all studies (30/32, 93.75%) showed the consumption of low-intensity sweeteners led to a significant reduction of different types of cariogenic bacteria. The results of the meta-analysis showed that consumption of low-intensity sweeteners led to a significant reduction of cariogenic bacteria in both dental plaque and saliva compared to no treatment.

CONCLUSION

The consumption of low-intensity sweeteners helps reduce cariogenic bacteria in dental plaque and saliva. There is limited clinical evidence regarding the role of high-intensity sweeteners in reducing cariogenic bacteria.

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.

Exploring xylitol as a low-salt alternative for effective inhibition of gelation in frozen egg yolks

Xylitol and NaCl were studied as alternative inhibitors of gelation in frozen egg yolks, considering the current dietary preference for low salt and low sucrose intake. The effects of different ratios of xylitol and NaCl on gelation were investigated. Compared to the control group, all treatment groups showed decreased egg yolk particle size and turbidity, increased solubility, surface hydrophobicity, λmax, and fluorescence intensity, reduced loss of free water, and enhanced yolk fluidity. The addition of xylitol and NaCl effectively prevented ice crystal growth, minimized protein denaturation caused by water loss, and formed complexes with proteins and water lost during freezing, thereby inhibiting the aggregation of protein molecules and the formation of gels. This study presents a novel and healthier strategy for inhibiting gelation of frozen egg yolk using xylitol and NaCl.

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.

Xylitol associated or not with fluoride: Is the action the same on de- and remineralization?

OBJECTIVES

This study evaluated the effect of xylitol combined or not with fluoride (F) on reduction of demineralization and increase of remineralization of shallow and deep artificial enamel lesions.

METHODS

Bovine enamel samples were allocated to the following solutions groups: no xylitol (negative control), 5% xylitol, 10% xylitol, 20% xylitol, 500 ppm F (as NaF), 5% xylitol+F, 10% xylitol+F or 20% xylitol+F (n = 12-15). For the demin study, a pH-cycling model (demineralization-6 h, pH 4.7/remineralization 18 h, pH 7.0) was employed for 7 days. Treatments were applied 2 × 1 min. In the remin study, specimens were pre-demineralized for 2, 5 or 10 days. Afterwards, a pH-cycling protocol was conducted (2 h demineralizing and 22 h remineralizing solution/day for 8 days) and the same treatments were done. The response variables were percentage surface hardness loss (%SHL) and transverse microradiography. Data were analyzed by RM ANOVA/Tukey or Kruskal-Wallis/Dunn (p < 0.05) RESULTS: F and Xylitol combined with F reduced the %SHL (23-30%) compared to the negative control (61.5%). The integrated mineral loss and the lesion depth were not reduced by any treatment. Surface hardness recovery was seen only for shallow lesions in case of 20% xylitol+F compared to negative control. No lesion depth recovery, but significant mineral recovery was seen for F (2-days and 10-days lesion).

CONCLUSIONS

All concentrations of xylitol+F reduced enamel surface demineralization, while only 20% xylitol+F improved surface remineralization of shallow lesions in vitro.

CLINICAL SIGNIFICANCE

Our results suggest that while F or any concentration of xylitol + F reduces surface demineralization, only 20% xylitol+F improves surface remineralization of shallow lesions in vitro. Therefore, xylitol may be added into oral products, combined to F, to control dental caries.

Bioprocess optimization for enhanced xylitol synthesis by new isolate Meyerozyma caribbica CP02 using rice straw

The present work models the fermentation process parameters of the newly isolated, Meyerozyma caribbica CP02 for enhanced xylitol production and its fermentability study on rice straw hydrolysate. The study examined the impact of each of the process variables by one variable at a time optimization followed by statistical validation. Temperature of 32 °C, pH of 3.5, agitation of 200 rpm, 1.5% (v/v) inoculum, 80 gL-1 initial xylose was optimized. Subsequently, a sequential two-stage agitation approach was adopted for fermentation. At these optimized conditions, xylitol yield of 0.77 gg-1 and 0.64 gg-1 was achieved using media containing commercial and rice straw derived xylose, respectively. For scale up, in 3L batch bioreactor, the highest xylitol yield (0.63 gg-1) was attained at 72 h with rice straw hydrolysate media containing initial xylose (59.48 ± 0.82 gL-1) along with inhibitors (1.55 ± 0.10 gL-1 aliphatic acids, 0.0.048 ± 0.11 gL-1 furans, 0.64 ± 0.23 gL-1 total phenols). The results imply that even under circumstances characterized by an acidic pH and elevated initial xylose level, M. caribbica CP02, as an isolate, displays robustness and shows favorable fermentability of rice straw hydrolysate. Therefore, isolate CP02 has potential to be used in bio-refineries for high yield xylitol production with minimal hydrolysate processing requirements.

Oxygenation influences xylose fermentation and gene expression in the yeast genera Spathaspora and Scheffersomyces

BACKGROUND

Cost-effective production of biofuels from lignocellulose requires the fermentation of D-xylose. Many yeast species within and closely related to the genera Spathaspora and Scheffersomyces (both of the order Serinales) natively assimilate and ferment xylose. Other species consume xylose inefficiently, leading to extracellular accumulation of xylitol. Xylitol excretion is thought to be due to the different cofactor requirements of the first two steps of xylose metabolism. Xylose reductase (XR) generally uses NADPH to reduce xylose to xylitol, while xylitol dehydrogenase (XDH) generally uses NAD+ to oxidize xylitol to xylulose, creating an imbalanced redox pathway. This imbalance is thought to be particularly consequential in hypoxic or anoxic environments.

RESULTS

We screened the growth of xylose-fermenting yeast species in high and moderate aeration and identified both ethanol producers and xylitol producers. Selected species were further characterized for their XR and XDH cofactor preferences by enzyme assays and gene expression patterns by RNA-Seq. Our data revealed that xylose metabolism is more redox balanced in some species, but it is strongly affected by oxygen levels. Under high aeration, most species switched from ethanol production to xylitol accumulation, despite the availability of ample oxygen to accept electrons from NADH. This switch was followed by decreases in enzyme activity and the expression of genes related to xylose metabolism, suggesting that bottlenecks in xylose fermentation are not always due to cofactor preferences. Finally, we expressed XYL genes from multiple Scheffersomyces species in a strain of Saccharomyces cerevisiae. Recombinant S. cerevisiae expressing XYL1 from Scheffersomyces xylosifermentans, which encodes an XR without a cofactor preference, showed improved anaerobic growth on xylose as the primary carbon source compared to S. cerevisiae strain expressing XYL genes from Scheffersomyces stipitis.

CONCLUSION

Collectively, our data do not support the hypothesis that xylitol accumulation occurs primarily due to differences in cofactor preferences between xylose reductase and xylitol dehydrogenase; instead, gene expression plays a major role in response to oxygen levels. We have also identified the yeast Sc. xylosifermentans as a potential source for genes that can be engineered into S. cerevisiae to improve xylose fermentation and biofuel production.

Effect of cryoanesthesia and sweet tasting solution in reducing injection pain in pediatric patients aged 7-10 years: a randomized controlled trial

Background

The delivery of profound local anesthetics helps children receive successful treatment by reducing fear, anxiety, and discomfort during dental procedures. Local anesthetic injections are the most anticipated stimuli in dental surgery. Children's perceptions of pain can be altered by applying cryotherapy to precool the oral mucosa or by diverting their minds through taste distractions before administering local anesthetic injections. This study aimed to evaluate the efficacy of cryoanesthesia and xylitol sweet-tasting solution at the injection site in 7-10-year-old children.

Methods

A total of 42 participants, aged 7-10 years, who underwent dental treatment requiring local anesthesia, were enrolled in the study. The children were randomly divided into three groups. In group I, sterile water was held in the mouth for 2 minutes before anesthetic administration, similar to group II, and in group III, a xylitol sweet-tasting solution was used for 2 minutes before needle insertion. The analysis of pain perception was carried out based on the Visual Analog Scale (VAS) and the Sound, Eyes, and Motor (SEM) scale. For VAS analysis, a one-way analysis of variance (ANOVA) was performed for intergroup comparison, and a post hoc Tukey test was performed for subgroup analysis. For the categorical SEM scale, the Kruskal-Wallis test followed by the post hoc test was performed for intergroup comparison. Where a P value of <0.05 was considered statistically significant at 95% confidence intervals.

Results

Cryoanesthesia significantly reduced pain scores on VAS (4.21 ± 1.42) when compared to those on VAS with xylitol sweet-tasting solution (5.50 ± 1.40) and that with sterile water (6.14 ± 2.47). Intergroup comparison of the VAS scores among the three groups was performed using one-way ANOVA, which demonstrated statistically significant differences (P value <0.026) on the VAS scale. Intergroup comparison of the SEM scale was performed using the Kruskal-Wallis test, followed by post hoc comparison, which exhibited statistically significant differences (P < 0.007) among the three groups for the SEM scale.

Conclusion

Cryoanesthesia demonstrated higher efficacy in reducing injection pain than that exhibited by the xylitol sweet-tasting solution.

Utilization of agricultural wastes for co-production of xylitol, ethanol, and phenylacetylcarbinol: A review

Corn, rice, wheat, and sugar are major sources of food calories consumption thus the massive agricultural waste (AW) is generated through agricultural and agro-industrial processing of these raw materials. Biological conversion is one of the most sustainable AW management technologies. The abundant supply and special structural composition of cellulose, hemicellulose, and lignin could provide great potential for waste biological conversion. Conversion of hemicellulose to xylitol, cellulose to ethanol, and utilization of remnant whole cells biomass to synthesize phenylacetylcarbinol (PAC) are strategies that are both eco-friendly and economically feasible. This co-production strategy includes essential steps: saccharification, detoxification, cultivation, and biotransformation. In this review, the implemented technologies on each unit step are described, the effectiveness, economic feasibility, technical procedures, and environmental impact are summarized, compared, and evaluated from an industrial scale viewpoint.

Detoxification Approaches of Bagasse Pith Hydrolysate Affecting Xylitol Production by Rhodotorula mucilaginosa

In this study, the potential of bagasse pith (the waste of sugar and paper industry) was investigated for bio-xylitol production for the first time. Xylose-rich hydrolysate was prepared using 8% dilute sulfuric acid, at 120 °C for 90 min. Then, the acid-hydrolyzed solution was detoxified by individual overliming (OL), active carbon (AC), and their combination (OL+AC). The amounts of reducing sugars and inhibitors (furfural and hydroxyl methyl furfural) were measured after acid pre-treatment and detoxification process. Thereafter, xylitol was produced from detoxified hydrolysate by Rhodotorula mucilaginosa yeast. Results showed that after acid hydrolysis, the sugar yield was 20%. Detoxification by overliming and active carbon methods increased the reducing sugar content up to 65% and 36% and decreased the concentration of inhibitors to >90% and 16%, respectively. Also, combined detoxification caused an increase in the reducing sugar content (>73%) and a complete removal of inhibitors. The highest productivity of xylitol (0.366 g/g) by yeast was attained after the addition of 100 g/l non-detoxified xylose-rich hydrolysate into fermentation broth after 96 h, while the xylitol productivity enhanced to 0.496 g/g after adding the similar amount of xylose-rich hydrolysate detoxified by combined method (OL+AC2.5%).

Tracking transformation behavior of soluble to insoluble components in liquid egg yolk under heat treatment and the intervention effect of xylitol

The heat sensitivity of egg yolk limits its application, and xylitol can improve its thermal stability. The soluble and insoluble components of egg yolk and egg yolk containing xylitol treated at different temperatures were explored from the aspects of thermal instability behavior characterization and structure property. Magnetic resonance imaging and low field nuclear magnetic resonance showed that increased temperature induced liberation and transfer of hydrogen protons. Meanwhile, the apparent viscosity of soluble components increased, while that of insoluble components decreased. Microstructure showed that heat treatment induced aggregation and lipid transfer. SDS-PAGE showed that heat treatment induced aggregation and transformation of γ-livetin and apo-LDL. The change in crystal structure, Raman spectroscopy, and 3D fluorescence spectra showed that heat treatment resulted in the unfolding of yolk proteins, especially plasma proteins. Xylitol could alleviate transformation of components by stabilizing protein structure, alleviating the damage in protein integrity and elevation in aggregation size.

Effects of electrospun nanofiber fabrications on immobilization of recombinant Escherichia coli for production of xylitol from glucose

A suitable nanofiber sheet was formulated and developed based on its efficacy in the immobilization of recombinant Escherichia coli (E. coli) to enhance xylitol production. The effects of different types of nanofibers and solvents on cell immobilization and xylitol production were studied. The most applicable nanofiber membrane was selected via preliminary screening of four types of nanofiber membrane, followed by the selection of six different solvents. Polyvinylidene fluoride (PVDF) nanofiber sheet synthesized using dimethylformamide (DMF) solvent was found to be the most suitable carrier for immobilization and xylitol production. The thin, beaded PVDF (DMF) nanofibers were more favourable for microbial adhesion, with the number of immobilized cells as high as 96 × 106 ± 3.0 cfu/ml. The attraction force between positively charged PVDF nanofibers and the negatively charged E. coli indicates that the electrostatic interaction plays a significant role in cell adsorption. The use of DMF has also produced PVDF nanofibers biocatalyst capable of synthesizing the highest xylitol concentration (2.168 g/l) and productivity (0.090 g/l/h) and 55-69% reduction in cell lysis compared with DMSO solvent and free cells. This finding suggests that recombinant E. coli immobilized on nanofibers shows great potential as a whole-cell biocatalyst for xylitol production.

Construction of a xylose metabolic pathway in Trichosporonoides oedocephalis ATCC 16958 for the production of erythritol and xylitol

PURPOSE

Erythritol is a valuable compound as sweetener and chemical material however cannot be fermented from the abundant substrate xylose.

METHODS

The strain Trichosporonoides oedocephalis ATCC 16958 was employed to produce polyols including xylitol and erythritol by metabolic engineering approaches.

RESULTS

The introduction of a substrate-specific ribose-5-phosphate isomerase endowed T. oedocephalis with xylose-assimilation activity to produce xylitol, and eliminated glycerol production simultaneously. A more value-added product, erythritol was produced by further introducing a homologous xylulose kinase. The carbon flux was redirected from xylitol to erythritol by adding high osmotic pressure. The production of erythritol was improved to 46.5 g/L in flasks by fermentation adjustment, and the process was scaled up in a 5-L fermentor, with a 40 g/L erythritol production after 120 h, and a time-space yield of 0.56 g/L/h.

CONCLUSION

This study demonstrated the potential of T. oedocephalis in the synthesis of multiple useful products from xylose.

Xylitol Production by Candida tropicalis from Areca Nut Husk Enzymatic Hydrolysate and Crystallization

Lignocellulosic biomasses are extensively used by researchers to produce a variety of renewable bioproducts. This research described an environment-friendly technique of xylitol production by an adapted strain of Candida tropicalis from areca nut hemicellulosic hydrolysate, produced through enzymatic hydrolysis. To enhance the activity of xylanase enzymes, lime and acid pretreatment was conducted to make biomass more amenable for saccharification. To improve the efficiency of enzymatic hydrolysis, saccharification parameters like xylanase enzyme loading were varied. Results exposed that the highest yield (g/g) of reducing sugar, about 90%, 83%, and 15%, were achieved for acid-treated husk (ATH), lime-treated husk (LTH), and raw husk (RH) at an enzyme loading of 15.0 IU/g. Hydrolysis was conducted at a substrate loading of 2% (w/V) at 30 °C, 100 rpm agitation, for 12 h hydrolysis time at pH 4.5 to 5.0. Subsequently, fermentation of xylose-rich hemicellulose hydrolysate was conducted with pentose utilizing the yeast Candida tropicalis to produce xylitol. The optimum concentration of xylitol was obtained at about 2.47 g/L, 3.83 g/L, and 5.88 g/L, with yields of approximately 71.02%, 76.78%, and 79.68% for raw fermentative hydrolysate (RFH), acid-treated fermentative hydrolysate (ATFH), and lime-treated fermentative gydrolysate (LTFH), respectively. Purification and crystallization were also conducted to separate xylitol crystals, followed by characterization like X-ray diffraction (XRD) and scanning electron microscopy (SEM) analysis. Results obtained from crystallization were auspicious, and about 85% pure xylitol crystal was obtained.

Xylitol binding to the M1 site of glucose isomerase induces a conformational change in the substrate binding channel

Glucose isomerase (GI) is extensively used in the food industry for production of high-fructose corn syrup and for the production of biofuels and other renewable chemicals. Structure-based studies on GI inhibitors are important for improving its efficiency in industrial applications. Here, we report the subatomic crystal structure of Streptomyces rubiginosus GI (SruGI) complexed with its inhibitor, xylitol, at 0.99 Å resolution. Electron density map and temperature factor analysis showed partial binding of xylitol to the M1 metal binding site of SruGI, providing two different conformations of the metal binding site and the substrate binding channel. The xylitol molecule induced a conformational change in the M2 metal ion-interacting Asp255 residue, which subsequently led to a conformational change in the side chain of Asp181 residue. This led to the positional shift of Pro25 by 1.71 Å and side chain rotation of Phe26 by 21°, where located on the neighboring protomer in tetrameric SruGI. The conformation change of these two residues affect the size of the substrate-binding channel of GI. Therefore, xylitol binding to M1 site of SruGI induces not only a conformational changes of the metal-binding site, but also conformational change of substrate-binding channel of the tetrameric SruGI. These results expand our knowledge about the mechanism underlying the inhibitory effect of xylitol on GI.

Isolation of xylose-utilizing yeasts from oil palm waste for xylitol and ethanol production

The energy crisis triggers the use of energy sources that are renewable, such as biomass made from lignocellulosic materials, to produce various chemical compounds for food ingredients and biofuel. The efficient conversion of lignocellulosic biomass into products with added value involves the activity of microorganisms, such as yeasts. For the conversion, microorganisms must be able to use various sugars in lignocellulosic biomass, including pentose sugars, especially xylose. This study aims to isolate xylose-utilizing yeasts and analyze their fermentation activity to produce xylitol and ethanol, as well as their ability to grow in liquid hydrolysate produced from pretreated lignocellulosic biomass. Nineteen yeast isolates could grow on solid and liquid media using solely xylose as a carbon source. All isolates can grow in a xylose medium with incubation at 30 °C, 37 °C, 42 °C, and 45 °C. Six isolates, namely SLI (1), SL3, SL6, SL7, R5, and OPT4B, were chosen based on their considerable growth and high xylose consumption rate in a medium with 50 g/L xylose with incubation at 30 °C for 48 h. Four isolates tested, namely SLI (1), SL6, SL7, and R5, can produce xylitol in media containing xylose carbon sources. The concentration of xylitol produced was determined using high-pressure liquid chromatography (HPLC), and the results ranged from 5.0 to 6.0 g/L. Five isolates tested, namely SLI (1), SL6, SL3, R5, and OPT4B, can produce ethanol. The ethanol content produced was determined using gas chromatography (GC), with concentrations ranging from 0.85 to 1.34 g/L. Three isolates, namely SL1(1), R5, and SL6, were able to produce xylitol and ethanol from xylose as carbon sources and were also able to grow on liquid hydrolyzate from pretreated oil palm trunk waste with the subcritical water method. The three isolates were further analyzed using the 18S rDNA sequence to identify the species and confirm their phylogenetic position. Identification based on DNA sequence analysis revealed that isolates SL1(1) and R5 were Pichia kudriavzevii, while isolate SL6 was Candida xylopsoci. The yeast strains isolated from this study could potentially be used for the bioconversion process of lignocellulosic biomass waste to produce value-added derivative products.

Development of engineered Candida tropicalis strain for efficient corncob-based xylitol-ethanol biorefinery

BACKGROUND

Xylitol has a wide range of applications in the pharmaceuticals, cosmetic, food and beverage industry. Microbial xylitol production reduces the risk of contamination and is considered as environment friendly and sustainable compared to the chemical method. In this study, random mutagenesis and genetic engineering approaches were employed to develop Candida tropicalis strains with reduced xylitol dehydrogenase (XDH) activity to eliminate co-substrate requirement for corn cob-based xylitol-ethanol biorefinery.

RESULTS

The results suggest that when pure xylose (10% w/v) was fermented in bioreactor, the Ethyl methane sulfonate (EMS) mutated strain (C. tropicalis K2M) showed 9.2% and XYL2 heterozygous (XYL2/xyl2Δ::FRT) strain (C. tropicalis K21D) showed 16% improvement in xylitol production compared to parental strain (C. tropicalis K2). Furthermore, 1.5-fold improvement (88.62 g/L to 132 g/L) in xylitol production was achieved by C. tropicalis K21D after Response Surface Methodology (RSM) and one factor at a time (OFAT) applied for media component optimization. Finally, corncob hydrolysate was tested for xylitol production in biorefinery mode, which leads to the production of 32.6 g/L xylitol from hemicellulosic fraction, 32.0 g/L ethanol from cellulosic fraction and 13.0 g/L animal feed.

CONCLUSIONS

This work, for the first time, illustrates the potential of C. tropicalis K21D as a microbial cell factory for efficient production of xylitol and ethanol via an integrated biorefinery framework by utilising lignocellulosic biomass with minimum waste generation.

Acceptance and awareness of southeastern and western private practice pediatric dentists of fluoride-free toothpastes: a survey study

The American Academy of Pediatric Dentistry (AAPD) affirms that the use of fluoride, as an adjunct in the prevention of caries, is safe and effective. The AAPD encourages dentists, other healthcare providers, and parents to optimize fluoride exposures to reduce the risk of caries and to enhance the remineralization of affected teeth. However, there is resistance amongst patients towards fluoride overexposure and despite there being research on other effective remineralizing agents, most pediatric dentists primarily cater their practice to fluoride-based products. The objective of the study is to survey pediatric dentists' acceptance and awareness of fluoride-free remineralizing agents. A listserv of the southeastern and western private practice pediatric dentists was obtained from the AAPD consisting of 6490 email addresses. A questionnaire consisting of 15 questions was sent to each address using Qualtrics. Different trends in fluoride-free acceptance and awareness were seen based on region of practice, region of training and age of practitioner. Region of practice, residency training and age can be contributing factors toward fluoride-free remineralizing agent opinion. The data gathered trends towards western-trained pediatric dentists are more likely to recommend a fluoride-free toothpaste than a southeastern-trained dentist.

Non-canonical D-xylose and L-arabinose metabolism via D-arabitol in the oleaginous yeast Rhodosporidium toruloides

R. toruloides is an oleaginous yeast, with diverse metabolic capacities and high tolerance for inhibitory compounds abundant in plant biomass hydrolysates. While R. toruloides grows on several pentose sugars and alcohols, further engineering of the native pathway is required for efficient conversion of biomass-derived sugars to higher value bioproducts. A previous high-throughput study inferred that R. toruloides possesses a non-canonical L-arabinose and D-xylose metabolism proceeding through D-arabitol and D-ribulose. In this study, we present a combination of genetic and metabolite data that refine and extend that model. Chiral separations definitively illustrate that D-arabitol is the enantiomer that accumulates under pentose metabolism. Deletion of putative D-arabitol-2-dehydrogenase (RTO4_9990) results in > 75% conversion of D-xylose to D-arabitol, and is growth-complemented on pentoses by heterologous xylulose kinase expression. Deletion of putative D-ribulose kinase (RTO4_14368) arrests all growth on any pentose tested. Analysis of several pentose dehydrogenase mutants elucidates a complex pathway with multiple enzymes mediating multiple different reactions in differing combinations, from which we also inferred a putative L-ribulose utilization pathway. Our results suggest that we have identified enzymes responsible for the majority of pathway flux, with additional unknown enzymes providing accessory activity at multiple steps. Further biochemical characterization of the enzymes described here will enable a more complete and quantitative understanding of R. toruloides pentose metabolism. These findings add to a growing understanding of the diversity and complexity of microbial pentose metabolism.

Natural deep eutectic solvents as thermostabilizer for Humicola insolens cutinase

As a new generation of green solvents, deep eutectic solvents (DESs) are considered a promising alternative to current harsh organic solvents and find application in many chemical processing methods such as extraction and synthesis. DESs, normally formed by two or more components via various hydrogen bond interactions, offer high potential as medium for biocatalysis reactions where they can improve efficiency by enhancing substrate solubility and the activity and stability of the enzymes. In the current study, the stabilization of Humicola insolens cutinase (HiC) in natural deep eutectic solvents (NADESs) was assessed. The best hydrogen bond donor among sorbitol, xylitol, erythritol, glycerol and ethylene glycol, and the best acceptor among betaine, choline chloride, choline acetate, choline dihydrogen citrate and tetramethylammonium chloride, were selected, evaluating binding energies and molecular orientations through molecular docking simulations, and finally used to prepare NADES aqueous solutions. The effects of component ratio and NADES concentration on HiC thermostability at 90 °C were also investigated. The choline dihydrogen citrate:xylitol, in a 1:1 ratio with a 20wt% concentration, was selected as the best combination in stabilizing HiC, increasing its half-life three-fold.

Rapidly evaluating the caking tendency of sugar alcohols by developing a crystal bridge growth model: A case study of xylitol

Caking of crystalline sugar alcohols is a deleterious and undesired agglomeration process during storage in the food industry. Compared with the time-consuming and labor-intensive conventional caking assessment methods, this work develops a rapid methodology for evaluation of the critical caking cycle of xylitol with over 85% time-saving and 90% labor-saving while guaranteeing the precision accuracy. By developing a Caking-Hygroscopicity-Particle size crystal bridge growth model, the correlation and quantitative relationships among hygroscopic properties, particle size and the critical caking cycle are firstly established and confirmed, which can greatly simplify the most time-consuming and laborious experiments of water sorption measurements and caking tests. Besides, the knowledge obtained can help guide the rapid selection of storage humidity conditions and appropriate particle size distributions for maintaining the desired properties and competitive marketability of crystalline sugar alcohols.

Hard Gelatin Capsules Containing Hot Melt Extruded Solid Crystal Suspension of Carbamazepine for improving dissolution: Preparation and In vitro Evaluation

Aqueous solubility is one of the key parameters for achieving the desired drug concentration in systemic circulation for better therapeutic outcomes. Carbamazepine (CBZ) is practically insoluble in water, is a BCS class II drug, and exhibits dissolution-dependent oral bioavailability. This study explored a novel application of hot-melt extrusion in the manufacture and development of a thermodynamically stable solid crystal suspension (SCS) to improve the solubility and dissolution rate of CBZ. The SCSs were prepared using sugar alcohols, such as mannitol or xylitol, as crystalline carriers. The drug-sugar blend was processed by hot melt extrusion up to 40 % (w/w) drug loading. The extruded SCS was evaluated for drug content, saturation solubility, differential scanning calorimetry (DSC), Fourier-transform infrared (FTIR) spectroscopy, powder X-ray diffraction (PXRD), scanning electron microscopy (SEM), in vitro release, and stability studies. The physicochemical characterization revealed the highly crystalline existence of pure drug, pure carriers, and extruded SCS. FTIR analysis did not reveal any physical or chemical incompatibilities between the drug and sugar alcohols and showed a homogeneous CBZ distribution within respective crystalline carriers. The SEM micrographs of the solidified SCS revealed the presence of approximately 100 μm crystalline agglomerates. In vitro dissolution and solubility studies showed that the CBZ dissolution rate and solubility were improved significantly from both crystalline carriers for all tested drug loads. The SCSs showed no significant changes in drug content, in vitro release profiles, and thermal characteristics over 3 months of storage at accelerated stability conditions (40±2°C/75±5% RH). As a result, it can be inferred that the SCS strategy can be employed as a contemporary alternative technique to improve the dissolution rate of BCS class II drugs via HME technology.

Synchronous Dual Electrolyte Additive Sustains Zn Metal Anode with 5600 h Lifespan

Despite conspicuous merits of Zn metal anodes, the commercialization is still handicapped by rampant dendrite formation and notorious side reaction. Manipulating the nucleation mode and deposition orientation of Zn is a key to rendering stabilized Zn anodes. Here, a dual electrolyte additive strategy is put forward via the direct cooperation of xylitol (XY) and graphene oxide (GO) species into typical zinc sulfate electrolyte. As verified by molecular dynamics simulations, the incorporated XY molecules could regulate the solvation structure of Zn²⁺ , thus inhibiting hydrogen evolution and side reactions. The self-assembled GO layer is in favor of facilitating the desolvation process to accelerate reaction kinetics. Progressive nucleation and orientational deposition can be realized under the synergistic modulation, enabling a dense and uniform Zn deposition. Consequently, symmetric cell based on dual additives harvests a highly reversible cycling of 5600 h at 1.0 mA cm^-2 /1.0 mAh cm^-2 .

Xylose Metabolization by a Saccharomyces cerevisiae Strain Isolated in Colombia

Saccharomyces cerevisiae (S. cerevisiae) is the most widely used yeast in biotechnology in the world because its well-known metabolism and physiology as well as its recognized ability to ferment sugars such as hexoses. However, it does not metabolize pentoses such as arabinose and xylose, which are present in lignocellulosic biomass. Lignocellulose is a widely available raw material, with xylose content of approximately 35% of total sugars. This xylose fraction could be used to obtain high added-value chemical products such as xylitol. One of these yeasts isolated from a Colombian locality, designated as 202-3, showed interesting properties. 202-3 was identified through different approaches as a strain of S. cerevisiae, with an interesting consumption of xylose metabolizing into xylitol, in addition with excellent ability as a hexose fermenter with high ethanol yields and shows resistance to inhibitors present in lignocellulosic hydrolysates. The xylose metabolization by the 202-3 strain and their kinetics parameters had not been previously reported for any other natural strain of S. cerevisiae. These results suggest the great potential of natural strains for obtaining high value-added chemical products using sugars available in lignocellulosic biomass.

Supplementary Information

The online version contains supplementary material available at 10.1007/s12088-023-01054-z.

Food-grade xylitol production from corncob biomass with acute oral toxicity studies

Xylitol, a sugar substitute, is widely used in various food formulations and finds a steady global market. In this study, xylitol crystals were produced from corncob by fermentation (as an alternative to the chemical catalytic process) by a GRAS yeast Pichia caribbica MTCC 5703 and characterized in detail for their purity and presence of any possible contaminant that may adversely affect mammalian cell growth and proliferation. The acute and chronic oral toxicity trials demonstrated no gross pathological changes with average weekly weight gain in female Wistar rats at high xylitol loading (LD₅₀ > 10,000 mg/kg body weight). The clinical chemistry analysis supported the evidence of no dose-dependent effect by analyzing blood biochemical parameters. The finding suggests the possible application of the crystals (> 98% purity) as a food-grade ingredient for commercial manufacture pending human trials.

Strategy to reduce acetic acid in sugarcane bagasse hemicellulose hydrolysate concomitantly with xylitol production by the promising yeast Cyberlindnera xylosilytica in a bioreactor

The yeast Cyberlindnera xylosilytica UFMG-CM-Y309 has been identified as a promising new xylitol producer from sugarcane bagasse hemicellulosic hydrolysate (SCHH). However, SCHH pretreatment process generates byproducts, which are toxic to cell metabolism, including furans, phenolic compounds, and carboxylic acids, such as acetic acid, typically released at high concentrations. This research aims to reduce acetic acid in sugarcane hemicellulose hydrolysate concomitantly with xylitol production by yeast strain Cy. xylosilytica UFMG-CM-Y309 in a bioreactor by strategically evaluating the influence of volumetric oxygen transfer coefficient (k_La) (21 and 35 h^-1). Experiments were conducted on a bench bioreactor (2 L volumetric capacity) at different initial k_La values (21 and 35 h^-1). SCHH medium was supplemented with rice bran extract (10 g L^-1) and yeast extract (1 g L^-1). Cy. xylosilytica showed high xylitol production performance (19.56 g L^-1), xylitol yield (0.56 g g^-1) and, maximum xylitol-specific production rate (μp_máx 0.20 g_xylitol·g^-1 h^-1) at k_La value of 21 h^-1, concomitantly slowing the rate of acetic acid consumption. A faster acetic acid consumption (100%) by Cy. xylosilytica was observed at k_La of 35 h^-1, concomitantly with an increase in maximum cellular growth (14.60 g L^-1) and reduction in maximum xylitol production (14.56 g L^-1 and Y_p/s 0.34 g g^-1). This study contributes to pioneering research regarding this yeast performance in bioreactors, emphasizing culture medium detoxification and xylitol production.

Multi-feedstock biorefinery concept: Valorization of winery wastes by engineered yeast

The wine industry produces significant amounts of by-products and residues that are not properly managed, posing an environmental problem. Grape must surplus, vine shoots, and wine lees have the potential to be used as renewable resources for the production of energy and chemicals. Metabolic engineering efforts have established Saccharomyces cerevisiae as an efficient microbial cell factory for biorefineries. Current biorefineries designed for producing multiple products often rely on just one feedstock, but the bioeconomy would clearly benefit if these biorefineries could efficiently convert multiple feedstocks. Moreover, to reduce the environmental impact of fossil fuel consumption and maximize production economics, a biorefinery should be capable to supplement the manufacture of biofuel with the production of high-value products. This study proposes an integrated approach for the valorization of diverse wastes resulting from winemaking processes through the biosynthesis of xylitol and ethanol. Using genetically modified S. cerevisiae strains, the xylose-rich hemicellulosic fraction of hydrothermally pretreated vine shoots was converted into xylitol, and the cellulosic fraction was used to produce bioethanol. In addition, grape must, enriched in sugars, was efficiently used as a low-cost source for yeast propagation. The production of xylitol was optimized, in a Simultaneous Saccharification and Fermentation process configuration, by adjusting the inoculum size and enzyme loading. Furthermore, a yeast strain displaying cellulases in the cell surface was applied for the production of bioethanol from the glucan-rich cellulosic. With the addition of grape must and/or wine lees, high ethanol concentrations were reached, which are crucial for the economic feasibility of distillation. This integrated multi-feedstock valorization provides a synergistic alternative for converting a range of winery wastes and by-products into biofuel and an added-value chemical while decreasing waste released to the environment.

Dietary Xylitol Supplement Ameliorated AD-related Neuronal Injury by Regulating Glucose Metabolism Relevant Amino Acids in Mice

BACKGROUND

Alzheimer's disease (AD) is one of the most common irreversible degenerative diseases of the central nervous system. Recent studies have found that patients with AD generally experience abnormal glucose metabolism. Xylitol is a functional sugar alcohol, which has been reported to regulate glucose metabolism.

OBJECTIVE

The present study was designed to determine whether xylitol can alleviate cognitive impairment in AD mice.

METHODS

In the current research, 5% xylitol was supplemented in the diet to treat APP/PS1 transgenic AD mice for 2 months. Cognitive ability was measured by the Morris water maze, and anxiety-like behaviors were examined by open-field experiment. Hippocampal cellular apoptosis and mitochondria pathway related apoptotic proteins were tested by TUNEL staining and immunoblotting, respectively. By LC-MS, plasma levels of glucose metabolism intermediates and related amino acids were evaluated.

RESULTS

Results showed that xylitol could significantly ameliorate anxiety-like activity in AD mice by partially regulating expression levels of mitochondrial pathway-related apoptotic proteins. Xylitolregulated glucose metabolism may play an important role in the process.

CONCLUSION

The current study suggests that xylitol may be a potential candidate for improving neuropsychiatric behavior in AD by regulating the levels of TCA cycle intermediates and related amino acids in glucose metabolism.

Techno-economic analysis of an integrated biorefinery to convert poplar into jet fuel, xylitol, and formic acid

BACKGROUND

The overall goal of the present study is to investigate the economics of an integrated biorefinery converting hybrid poplar into jet fuel, xylitol, and formic acid. The process employs a combination of integrated biological, thermochemical, and electrochemical conversion pathways to convert the carbohydrates in poplar into jet fuel, xylitol, and formic acid production. The C5-sugars are converted into xylitol via hydrogenation. The C6-sugars are converted into jet fuel via fermentation into ethanol, followed by dehydration, oligomerization, and hydrogenation into jet fuel. CO₂ produced during fermentation is converted into formic acid via electrolysis, thus, avoiding emissions and improving the process's overall carbon conversion.

RESULTS

Three different biorefinery scales are considered: small, intermediate, and large, assuming feedstock supplies of 150, 250, and 760 dry ktonne of poplar/year, respectively. For the intermediate-scale biorefinery, a minimum jet fuel selling price of $3.13/gallon was obtained at a discount rate of 15%. In a favorable scenario where the xylitol price is 25% higher than its current market value, a jet fuel selling price of $0.64/gallon was obtained. Co-locating the biorefinery with a power plant reduces the jet fuel selling price from $3.13 to $1.03 per gallon.

CONCLUSION

A unique integrated biorefinery to produce jet fuel was successfully modeled. Analysis of the biorefinery scales shows that the minimum jet fuel selling price for profitability decreases with increasing biorefinery scale, and for all scales, the biorefinery presents favorable economics, leading to a minimum jet fuel selling price lower than the current price for sustainable aviation fuel (SAF). The amount of xylitol and formic produced in a large-scale facility corresponds to 43% and 25%, respectively, of the global market volume of these products. These volumes will saturate the markets, making them infeasible scenarios. In contrast, the small and intermediate-scale biorefineries have product volumes that would not saturate current markets, does not present a feedstock availability problem, and produce jet fuel at a favorable price given the current SAF policy support. It is shown that the price of co-products greatly influences the minimum selling price of jet fuel, and co-location can further reduce the price of jet fuel.

Improving glycerol utilization during high-temperature xylitol production with Kluyveromyces marxianus using a transient clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated protein 9 system

Glycerol is an ideal co-substrate for xylitol production with Kluyveromyces marxianus. This study demonstrated that K. marxianus catabolizes glycerol through the Gut1-Gut2 pathway instead of the previously speculated NADPH-dependent Gcy1-Dak1 pathway using the transient clustered regularly interspaced short palindromic repeats/ CRISPR-associated protein 9 (CRISPR/Cas9) system. Additionally, Utr1p was demonstrated to mediate NADPH generation through NADH phosphorylation. YZB392, which was constructed by integrating Utr1 into the Ypr1 site in the strain overexpressing NcXyl1 and CiGxf1 and harboring disrupted Xyl2, exhibited enhanced glycerol utilization for xylitol production (from 2.50- to 3.30- g/L after consuming 1 g/L glycerol). Fed-batch fermentation at 42 °C with YZB392 yielded 322.07 g/L xylitol, which is the highest known xylitol titer obtained via biological method. Feeding crude glycerol, xylose mother liquor, and corn steep liquor powder into a bioreactor resulted in the production of 235.69 g/L xylitol. This study developed a platform for xylitol production from industrial by-products.

Effects of sugar-free polyol chewing gums on gingival inflammation: a systematic review

OBJECTIVES

A systematic review of published data was conducted with the aim of assessing the effects of sugar-free polyol chewing gums on gingival inflammation.

MATERIALS AND METHODS

Electronic and hand searches were performed to find clinical studies concerning the effects of sugar-free chewing gums on gingival scores. Prospective randomized controlled clinical trials published between 1971 and 2021 were included in the review.

RESULTS

The initial search identified 46 erythritol, 102 xylitol, 23 sorbitol, and nine maltitol chewing gum articles. After applying inclusion and exclusion criteria, seven xylitol chewing gum studies, one sorbitol, and one maltitol chewing gum study with either high or fair quality were reviewed. In five out of the seven xylitol studies, xylitol gum decreased gingival scores. In two studies, xylitol decreased gingival scores compared to a polyol gum, and in three studies compared to no gum/gum base. As for sorbitol and maltitol, only sorbitol gum chewing showed a small decrease in gingival scores compared to the controls.

CONCLUSIONS

Habitual xylitol gum chewing may reduce gingival inflammation. The low number of studies and their heterogeneity provide clear indications that the effects of sugar-free polyol chewing gums on gingival inflammation need further, well-controlled studies.

CLINICAL RELEVANCE

Sugar-free chewing gums, especially xylitol gum, may function as adjuncts to toothbrushing for reducing gingival inflammation, but the evidence so far is inconclusive.

Antimicrobial efficacy of Xylitol, Probiotic and Chlorhexidine mouth rinses among children and elderly population at high risk for dental caries - A Randomized Controlled Trial

Introduction

Chlorhexidine is considered the most potent chemotherapeutic agent against Streptococcus mutans. However, its side effects due to prolonged use, indicates need for alternatives. The study intended to assess and compare antimicrobial efficacies of probiotic, xylitol and chlorhexidine mouth rinses in children and elderly.

Methods

The study was a Double blind Randomized Controlled Trial conducted among residential school children aged 5-12 years and elderly greater than 60 years residing in old age homes. (ClinicalTrials.gov ID: NCT04399161). 30 participants each among children and elderly were chosen based on eligibility criterion (high risk for caries). They were further randomly divided into 3 groups with 10 participants in each group. Participants were asked to rinse with 15 ml of freshly prepared mouth rinses once daily for 2 minutes for 14 days. Antimicrobial efficacy was determined by assessing change in Streptococcus mutans levels in dental plaque.

Results

Significant reduction in Streptococcus mutans counts were observed in both children and elderly (Chlorhexidine: mean difference = 3.11 log10CFU/g, p = 0.022, Xylitol: mean difference = 0.93 log10CFU/g, p = 0.046, Probiotic: mean difference = 1.91 log10CFU/g, p = 0.023 in children); (Chlorhexidine: mean difference = 2.23 log10CFU/g, p = 0.004, Xylitol: mean difference = 1.39 log10CFU/g, p = 0.009, Probiotic: mean difference = 1.61 log10CFU/g, p = 0.018 in elderly). Intergroup comparison showed no significant difference.

Conclusions

Antimicrobial efficacy of xylitol and probiotic mouth rinses were comparable to that of chlorhexidine in both children and elderly. Probiotics could potentially be more efficacious than xylitol among children.

Fermentation performance of a Mexican native Clavispora lusitaniae strain for xylitol and ethanol production from xylose, glucose and cellobiose

Lignocellulose hydrolysates are rich in fermentable sugars such as xylose, cellobiose and glucose, with high potential in the biotechnology industry to obtain bioproducts of higher economic value. Thus, it is important to search for and study new yeast strains that co-consume these sugars to achieve better yields and productivity in the processes. The yeast Clavispora lusitaniae CDBB-L-2031, a native strain isolated from mezcal must, was studied under various culture conditions to potentially produce ethanol and xylitol due to its ability to assimilate xylose, cellobiose and glucose. This yeast produced ethanol under microaerobic conditions with yields of 0.451 g_ethanol/g_glucose and 0.344 g_ethanol/g_cellobiose, when grown on 1% glucose or cellobiose, respectively. In mixtures (0.5% each) of glucose:xylose and glucose:xylose:cellobiose the yields were 0.367 g_ethanol/g_GX and 0. 380 g_ethanol/g_GXC, respectively. Likewise, in identical conditions, C. lusitaniae produced xylitol from xylose with a yield of 0.421 g_xylitol/g_xylose. In 5% glucose or xylose, this yeast had better ethanol and xylitol titers and yields, respectively. However, glucose negatively affected xylitol production in the mixture of both sugars (3% each), producing only ethanol. Xylose reductase (XR) and xylitol dehydrogenase (XDH) activities were evaluated in cultures growing on xylose or glucose, obtaining the highest values in cultures on xylose at 8 h (25.9 and 6.22 mU/mg, respectively). While in glucose cultures, XR and XDH activities were detected once this substrate was consumed (4.06 and 3.32 mU/mg, respectively). Finally, the XYL1 and XYL2 genes encoding xylose reductase and xylitol dehydrogenase, respectively, were up-regulated by xylose, whereas glucose down-regulated their expression.

Effectiveness of pediatric nasal irrigation solution with or without xylitol

OBJECTIVES

/Hypothesis: The aim of this study was to compare the efficacy and outcome of daily hypertonic saline irrigation versus saline/xylitol for treating pediatric chronic rhinosinusitis (CRS).

STUDY DESIGN

This was a prospective, randomized, single-blinded study.

METHODS

One hundred and twenty-five children diagnosed with CRS were enrolled in this study. The patients were randomized to twice-daily hypertonic irrigations with saline or saline/xylitol for 6 weeks. The treatment outcomes were measured using: Sinonasal Quality of Life Survey (SN-5) completed at baseline and after 6 weeks of irrigation.

RESULTS

There were statistically significant improvements in the hypertonic nasal saline group's (reduction in SN-5 domain scores) four domains and an increase in the overall QoL score within each group after 6 weeks of treatment compared to baseline; however, there were no differences in the activity limitation (p = 0.1803). The xylitol solution groups had no differences between the two groups in the SN-5 scores in any of the domains or the overall score at baseline, and post irrigation treatment.

CONCLUSIONS

Due to low tolerance, compliance, and the side effects, xylitol irrigation is not recommended as a first-line treatment for pediatric CRS. The use of a large volume of low pressure, twice-daily intranasal hypertonic irrigation for 6 weeks is safe and effective in the treatment of pediatric CRS; therefore, it can be used as a baseline treatment for pediatric CRS before considering surgical interventions.

Using maltitol and xylitol as alternative bulking agents in milk chocolate: modelling approach

The aim of the present study was to evaluate optimal concentration of polyols (maltitol and xylitol) by applying mixture design for the formulation of milk chocolate. The influences of polyols as sucrose substitutes on the main physicochemical parameters and sensory perception were determined. The optimization of the variables demonstrated that utilizing 85.58% maltitol and 14.42% xylitol yielded the optimum milk chocolate with the highest desirability without unpleasant alterations in the quality characteristics. Chocolates possessing high concentrations of maltitol pleased the consumer demand. The outcomes indicated that sucrose replacement by polyols have potential in the formulation of reduced calorie milk chocolates.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s13197-021-05268-1.

cerevisiae: towards xylitol production from sugarcane straw

Background

Sugarcane hemicellulosic material is a compelling source of usually neglected xylose that could figure as feedstock to produce chemical building blocks of high economic value, such as xylitol. In this context, Saccharomyces cerevisiae strains typically used in the Brazilian bioethanol industry are a robust chassis for genetic engineering, given their robustness towards harsh operational conditions and outstanding fermentation performance. Nevertheless, there are no reports on the use of these strains for xylitol production using sugarcane hydrolysate.

Results

Potential single-guided RNA off-targets were analyzed in two preeminent industrial strains (PE-2 and SA-1), providing a database of 5′-NGG 20 nucleotide sequences and guidelines for the fast and cost-effective CRISPR editing of such strains. After genomic integration of a NADPH-preferring xylose reductase (XR), FMYX (SA-1 hoΔ::xyl1) and CENPKX (CEN.PK-122 hoΔ::xyl1) were tested in varying cultivation conditions for xylitol productivity to infer influence of the genetic background. Near-theoretical yields were achieved for all strains; however, the industrial consistently outperformed the laboratory strain. Batch fermentation of raw sugarcane straw hydrolysate with remaining solid particles represented a challenge for xylose metabolization, and 3.65 ± 0.16 g/L xylitol titer was achieved by FMYX. Finally, quantification of NADPH — cofactor implied in XR activity — revealed that FMYX has 33% more available cofactors than CENPKX.

Conclusions

Although widely used in several S. cerevisiae strains, this is the first report of CRISPR-Cas9 editing major yeast of the Brazilian bioethanol industry. Fermentative assays of xylose consumption revealed that NADPH availability is closely related to mutant strains’ performance. We also pioneer the use of sugarcane straw as a substrate for xylitol production. Finally, we demonstrate how industrial background SA-1 is a compelling chassis for the second-generation industry, given its inhibitor tolerance and better redox environment that may favor production of reduced sugars.

Supplementary Information

The online version contains supplementary material available at 10.1186/s43141-022-00359-8.

Integrated production of ethanol and xylitol from Brassica juncea using Candida sojae JCM 1644

The present study demonstrates a novel strategy involving two-step fermentation of lignocellulosic hydrolysate for the integrated production of ethanol and xylitol using a newly isolated yeast strain, Candida sojae JCM 1644. The isolated strain was characterised by its carbohydrate assimilation efficiency and tolerance towards inhibitors generated during pretreatment and fermentation of lignocellulosic biomass. In brief, the study comprised alkali treatment of Brassica juncea followed by its saccharification with cellulase consortia. An isolated strain was used for the co-production of xylitol and ethanol from sugar hydrolysate, and several parameters were systematically optimised for maximum co-production of ethanol and xylitol. Out of total glucose (149.72 g/L) and xylose (84.21 g/L) present in biomass hydrolysate, a product yield of 0.45 g/g (ethanol) and 0.62 g/g (xylitol) was achieved for a two-step fermentation process, which was 15.57% and 11.78% higher than the yield achieved for ethanol and xylitol, respectively, in a one-step fermentation process.

Xylose and yeasts: A story beyond xylitol production

Six different yeasts were used to study their metabolism of glucose and xylose, and mainly their capacity to produce ethanol and xylitol. The strains used were Candida guilliermondii, Debaryomyces hansenii, Saccharomyces cerevisiae, Kluyveromyces marxianus, Meyerozyma guilliermondii and Clavispora lusitaniae, four isolated from a rural mezcal fermentation facility. All of them produced ethanol when the substrate was glucose. When incubated in a medium containing xylose instead of glucose, only K. marxianus and M. guilliermondii were able to produce ethanol from xylose. On the other hand, all of them could produce some xylitol from xylose, but the most active in this regard were K. marxianus, M. guilliermondii, Candida lusitaniae, and C. guilliermondii with the highest amount of xylitol produced. The capacity of all strains to take up glucose and xylose was also studied. Xylose, in different degrees, produced a redox imbalance in all yeasts. Respiration capacity was also studied with glucose or xylose, where C. guilliermondii, D. hansenii, K. marxianus and M. guilliermondii showed higher cyanide resistant respiration when grown in xylose. Neither xylose transport nor xylitol production were enhanced by an acidic environment (pH 4), which can be interpreted as the absence of a proton/sugar symporter mechanism for xylose transport, except for C. lusitaniae. The effects produced by xylose and their magnitude depend on the background of the studied yeast and the conditions in which these are studied.

Xylitol production by Pseudomonas gessardii VXlt-16 from sugarcane bagasse hydrolysate and cost analysis

Xylitol is a well-known sugar alcohol with exponentially rising market demand due to its diverse industrial applications. Organic agro-industrial residues (OAIR) are economic alternative for the cost-effective production of commodity products along with addressing environmental pollution. The present study aimed to design a process for xylitol production from OAIR via microbial fermentation with Pseudomonas gessardii VXlt-16. Parametric analysis with Taguchi orthogonal array approach resulted in a conversion factor of 0.64 g xylitol/g xylose available in untreated sugarcane bagasse hydrolysate (SBH). At bench scale, the product yield increased to 71.98/100 g (0.66 g/L h). 48.49 g of xylitol crystals of high purity (94.56%) were recovered after detoxification with 2% activated carbon. Cost analysis identified downstream operations as one of the cost-intensive parts that can be countered by adsorbent recycling. Spent carbon, regenerated with acetic acid washing can be reused for six cycles effectively and reduced downstream cost by about ≈32%. The strategy would become useful in the cost-effective production of several biomass-dependent products like proteins, enzymes, organic acids, as well.

An overview of the metabolically engineered strains and innovative processes used for the value addition of biomass derived xylose to xylitol and xylonic acid

Xylose, the most abundant pentose sugar of the hemicellulosic fraction of lignocellulosic biomass, has to be utilized rationally for the commercial viability of biorefineries. An effective pre-treatment strategy for the release of xylose from the biomass and an appropriate microbe of the status of an Industrial strain for the utilization of this pentose sugar are key challenges which need special attention for the economic success of the biomass value addition to chemicals. Xylitol and xylonic acid, the alcohol and acid derivatives of xylose are highly demanded commodity chemicals globally with plenty of applications in the food and pharma industries. This review emphasis on the natural and metabolically engineered strains utilizing xylose and the progressive and innovative fermentation strategies for the production and subsequent recovery of the above said chemicals from pre-treated biomass medium.

Microbial xylitol production

Xylitol is pentahydroxy sugar alcohol, existing in very trace amount in fruits and vegetables, and finds varied application in industries like food, pharmaceuticals, confectionaries, etc. and is of prime importance to health. Owing to its trace occurrence in nature and considerable increase in market demand that exceeds availability, alternate production through biotechnological and chemical approach is in process. Biochemical production involves substrates like lignocellulosic biomasses and industrial effluents and is an eco-friendly process with high dependency on physico-chemical parameters. Although the chemical processes are faster, high yielding and economical, they have a great limitation as usage of toxic chemicals and thus need to be regulated and replaced by an environment friendly approach. Microbes play a major role in xylitol production through a biotechnological process towards the development of a sustainable system. Major microbes working on assimilation of xylose for production of xylitol include Candida tropicalis, Candida maltose, Bacillus subtilis, Debaromyces hansenii, etc. The present review reports all probable microbial xylitol production biochemical pathways encompassing diverse bioprocesses involved in uptake and conversion of xylose sugars from agricultural residues and industrial effluents. A comprehensive report on xylitol occurrence and biotechnological production processes with varied substrates has been encompassed. KEY POINTS: • Xylitol from agro-industrial waste • Microbial xylose assimilation.

Comparison of Antibacterial Effect of Probiotic Yogurt and Xylitol-Containing Chewing Gum in Geriatric Patients: A Randomized Controlled Clinical Trial

Objectives

To evaluate the effect of probiotic bacteria in yogurt on Streptococcus mutans (MS) count, plaque adherence and salivary pH compared to xylitol-containing chewing gum in geriatric patients.

Materials and methods

Total number of 96 high caries risk geriatric patients were randomized into two equal groups (n=48). Group 1 (intervention group) received probiotic yogurt (Activia, Danone) once per day, and group 2 (control group) received xylitol chewing gum (Trident original) three times per day. The primary outcome was salivary Streptococcus mutans count and secondary outcomes were interdental plaque Streptococcus mutans count, salivary pH and bacterial adherence.

Results

For Streptococcus mutans count in saliva and plaque, a statistically significant reduction in the level of MS over all the examined follow up periods of the study in probiotic yogurt group as well as xylitol gum group was found. An intergroup comparison for salivary MS count showed statistically significant difference between the two materials in a two week and a three month period of time and there was no statistically significant difference between both materials at one month time period. Salivary pH results showed statistically significant increase in pH in both groups along the follow-up periods. Bacterial adherence results showed statistically significant reduction in both groups.

Conclusions

Probiotic yogurt is an effective antibacterial agent against salivary and plaque bacteria in geriatric patients.

Analysis of glucose and xylose metabolism in new indigenous Meyerozyma caribbica strains isolated from corn residues

Aiming to broaden the base of knowledge about wild yeasts, four new indigenous strains were isolated from corn residues, and phylogenetic-tree assemblings on ITS and LSU regions indicated they belong to Meyerozyma caribbica. Yeasts were cultivated under full- and micro-aerobiosis, starting with low or high cell-density inoculum, in synthetic medium or corn hydrolysate containing glucose and/or xylose. Cells were able to assimilate both monosaccharides, albeit by different metabolic routes (fermentative or respiratory). They grew faster in glucose, with lag phases ~ 10 h shorter than in xylose. The hexose exhaustion occurred between 24 and 34 h, while xylose was entirely consumed in the last few hours of cultivation (44-48 h). In batch fermentation in synthetic medium with high cell density, under full-aerobiosis, 18-20 g glucose l^-1 were exhausted in 4-6 h, with a production of 6.5-7.0 g ethanol l^-1. In the xylose medium, cells needed > 12 h to consume the carbohydrate, and instead of ethanol, cells released 4.4-6.4 g l^-1 xylitol. Under micro-aerobiosis, yeasts were unable to assimilate xylose, and glucose was more slowly consumed, although the ethanol yield was the theoretical maximum. When inoculated into the hydrolysate, cells needed 4-6 h to deplete glucose, and xylose had a maximum consumption of 57%. Considering that the hydrolysate contained ~ 3 g l^-1 acetic acid, it probably has impaired sugar metabolism. Thus, this study increases the fund of knowledge regarding indigenous yeasts and reveals the biotechnological potential of these strains.

High level xylitol production by Pichia fermentans using non-detoxified xylose-rich sugarcane bagasse and olive pits hydrolysates

Hemicellulosic sugars, the overlooked fraction of lignocellulosic residues can serve as potential and cost-effective raw material that can be exploited for xylitol production. Xylitol is a top platform chemical with applications in food and pharmaceutical industries. Sugarcane bagasse (SCB) and olive pits (OP) are the major waste streams from sugar and olive oil industries, respectively. The current study evaluated the potential of Pichia fermentans for manufacturing of xylitol from SCB and OP hydrolysates through co-fermentation strategy. The highest xylitol accumulation was noticed with a glucose and xylose ratio of 1:10 followed by feeding with xylose alone. The fed-batch cultivation using pure xylose, SCB, and OP hydrolysates, resulted in xylitol accumulation of 102.5, 86.6 and 71.9 g/L with conversion yield of 0.78, 0.75 and 0.74 g/g, respectively. The non-pathogenic behaviour and ability to accumulate high xylitol levels from agro-industrial residues demonstrates the potential of P. fermentans as microbial cell factory.

High humidity aggravates the severity of arthritis in collagen-induced arthritis mice by upregulating xylitol and L-pyroglutamic acid

Background

Humidity was an unfavorable factor for patients with rheumatoid arthritis (RA). RA disease activity was severe in high humidity conditions. However, there is no evidence to demonstrate the effects of humidity on arthritis in the animal experiments and explore its relevant mechanism.

Methods

Using the DBA/1 mice, this study addressed the effects of a high humidity (80 ± 5%) on arthritis in collagen-induced arthritis (CIA) mice. Then, this study used the gas chromatography-mass spectrometer (GC-MS) to explore alterations in serum metabolome caused by the high humidity. Furthermore, xylitol and L-pyroglutamic acid, which were both significantly upregulated by the high humidity, were selected to further study their effects on arthritis in the CIA mice.

Results

The high humidity (80 ± 5%) could aggravate arthritis variables including increasing arthritis score and swelling, serum autoantibodies (anti-COII and anti-CCP), and proinflammatory cytokines (IL-6, IL-17A, and G-CSF). In addition, the high humidity could cause significant alterations in serum metabolome in the CIA mice. Xylitol and L-pyroglutamic acid were the representative serum metabolites that were significantly upregulated by the high humidity. Further experiments demonstrated that the supplementation of 0.4 mg/mL xylitol in drinking water after inducing the CIA model and 2.0 mg/mL in drinking water before inducing the CIA model could both aggravate arthritis in the CIA mice.

Conclusions

These data demonstrated that high humidity was not beneficial for arthritis development and its mechanism might be associated with xylitol and L-pyroglutamic acid.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13075-021-02681-x.

Effects of Xylitol and CPP-ACP Chewing Gum on Salivary Properties of Children with Molar Incisor Hypomineralization

Aim

To compare the efficacy of chewing gum containing casein phosphopeptide-amorphous calcium phosphate (CPP-ACP) and xylitol on salivary characteristics in 8–10 years old children with molar incisor hypomineralization.

Materials and methods

A randomized controlled trial using CPP-ACP chewing gums (group I) and xylitol chewing gums (group II) was conducted among 32 children affected with mild molarincisor hypomineralization (MIH). Salivary flow rate, pH and buffering capacity were measured using saliva check kit (GC America). Data obtained were tabulated and subjected to statistical analysis using SPSS software version 20. Descriptive statistics–mean, standard deviation, 95% confidence interval. Inferential statistics–independent t tests were used.

Results

A significant increase in mean salivary pH, flow rate and buffering action was observed from baseline to immediately after spitting the chewing gum in both the study groups (p 0.05).

Conclusion

Casein phosphopeptide-amorphous calcium phosphate containing chewing gums improve salivary characteristics in MIH-affected children.

Clinical significance

Xylitol and CPP-ACP chewing gums are recommended in MIH children with early demarcated opacities as it improves the salivary properties in those children and prevents further complications.

How to cite this article

Prathima GS, Narmatha M, Selvabalaji A, et al. Effects of Xylitol and CPP-ACP Chewing Gum on Salivary Properties of Children with Molar Incisor Hypomineralization. Int J Clin Pediatr Dent 2021;14(3):412–415.

Particle size influence on the composition of sugars in corncob hemicellulose hydrolysate for xylose fermentation by Meyerozyma caribbica

The xylitol production was performed with acidophilic Meyerozyma caribbica. The particle size of 0.02 ± 0.01 to 0.1 ± 0.05 mm was rich in glucose (12.0 ± 0.5 g/L), whereas 0.5 ± 0.25 to 2.0 ± 0.5 mm had a high content of xylose (8.0 ± 0.5 g/L). The xylitol production in the synthetic, non-detoxified and detoxified hydrolysate media was studied (50 ± 0.5 g/L) using 10% v/v non - induced cells of M. caribbica for 120 h. At the end of fermentation with the specific growth rate of 0.056 ± 0.01 (μ), xylitol yields of 45.00 ± 1.00%, 10.00 ± 1.00% and 54.00 ± 1.00% were obtained. The detoxification of the hydrolysate prepared using an identified corncob particle size of 0.5 ± 0.25 to 2.0 ± 0.5 mm could be used as the prospective pretreatment process for ecofriendly and industrial scale production of xylitol with M. caribbica.

Effects of xylitol chewing gum and candies on the accumulation of dental plaque: a systematic review

Objectives

A systematic review of published data was conducted with the aim of assessing the effects of xylitol consumption on the amount of dental plaque.

Materials and methods

Electronic and hand searches were performed to find clinical studies concerning the effects of xylitol chewing gum or candies on dental plaque. Prospective randomized controlled clinical trials published between 1971 and 2020 conducted in healthy subjects were included in the review.

Results

The initial search identified 424 xylitol articles. After applying inclusion and exclusion criteria, altogether 14 articles (16 studies) were reviewed. The review identified 12 of the total of 14 xylitol chewing gum studies as having fair or high quality. In 13 of the 14 chewing gum studies, xylitol gum decreased plaque accumulation. In six studies, xylitol gum chewing decreased plaque compared to sorbitol gum, and in three studies compared to gum base/no gum. In three fair-quality studies conducted with xylitol candies, plaque accumulation did not change.

Conclusions

Habitual xylitol gum chewing appears to show plaque-reducing effects that differ from those of sorbitol gum. This suggests specific effects for xylitol on plaque accumulation. Xylitol candies appear not to decrease plaque. The heterogeneity of the studies warrants further research.

Clinical relevance

Habitual xylitol gum chewing is likely to decrease plaque.