The Emulsifying Properties of Hydrogenated Rosin Xylitol Ester as a Biomass Surfactant for Food: Effect of pH and Salts.

The xylitol ester of hydrogenated rosin (XEHR) was obtained for the first time from biomass-based hydrogenated rosin and xylitol using an environmentally friendly, high-pressure CO2 catalytic synthesis. This compound is intended for use as an emulsifier for food. Analyses by ICP-AES showed the absence of heavy metal residues in the product, such that it met food standards. Fourier transform infrared and nuclear magnetic resonance spectroscopies together with gel permeation chromatography confirmed the successful esterification and the formation of a monoester and diester with molar masses of 427 and 772 g/mol. The emulsification of water/soybean oil mixtures by adding the XEHR was assessed at pH values of 4, 6.86, and 10 and in the presence of NaCl, KCl, MgCl2, and CaCl2. The XEHR was found to act as an emulsifier by reducing the interfacial tension of such mixtures to less than 2 mN/m under all conditions. The highest emulsifying activity index (9.52 m2/g) and emulsifying stability index (94.53%) were obtained after adding MgCl2 (100 mM). Particle size and confocal microscopy showed that the presence of salts gave a more uniform droplet size and a finer emulsion structure. The high viscosities of the emulsions containing salts also suggested a more cohesive oil droplet network.

Xylitol, mannitol and maltitol as potential sucrose replacers in burger buns.

Burger buns are a source of added sugar, containing 7-12%, in order to ensure their unique texture and taste. Hence, suitable sugar substitutes for burger buns are urgently needed. This study aimed to elucidate the effect of three different polyols on dough and product quality of burger buns. Xylitol, mannitol and maltitol were incorporated individually in a burger bun system, by replacing added sucrose by 30%, 50% and 100%. Wheat starch was used to compare the impact of polyols with another non-sweet bulking agent. The effects on dough properties as well as on the burger buns themselves were investigated. Compared to sugar-rich doughs, polyols lowered the fermentation quality, resulting in lower dough development (-37 to -81%) and poorer gaseous release (-62 to -87%). Furthermore, a delay in gluten network development (+50 to +161%) and a decrease in extensibility (-14 to -18%) with increasing concentrations were detected. Interestingly, maltitol and xylitol did not affect the pasting properties, whereas mannitol increased pasting temperature (+15 °C). Moreover, polyols did not influence the viscoelastic properties of the dough. The incorporation of sugar alcohols led to a significant decrease in specific volume (-30 to -48%), and to a harder crumb texture (+135 to +678%). Moreover, the L*-value increased with increasing amount of polyols, resulting in a very pale crust colour. In conclusion, a reduction of 50% added sucrose by polyols was applicable, whereas mannitol was the most suitable sugar replacer amongst the polyols tested.

The early nucleation stage of gold nanoparticles formation in solution as powerful tool for the colorimetric determination of reducing agents: The case of xylitol and total polyols in oral fluid.

Herein we report a simple non-enzymatic assay for xylitol and total polyols in water and oral fluid based on the time resolved formation of gold NPs in solution, and their colorimetric detection at fixed wavelength (520 nm). The key novelty of the proposed approach relies on the exploitation of information given by the early nucleation step of NPs formation instead of those related to final products at the end point of AuNPs growth, as generally reported in literature. We demonstrate that the nucleation stage is linearly correlated to the concentration of the reducing agent in solution. On the contrary, the optical reading carried out the end point of the reaction shows non-linear correlation and several undesired features. As case study, we applied the proposed method to xylitol and polyols determination, first tested in water and spiked oral fluid samples. The detection limits obtained on xylitol resulted 180 mg L-1 (CV% = 6.9) and 44 mg L-1 (CV% = 6.5) in water and oral fluid, respectively. Afterward, we successfully performed the monitoring of total polyols in oral fluid over time during xylitol-containing gums consumption. Data here reported show high correspondence with available data in literature. The proposed approach is fast, cheap, highly reproducible, and can be extended to other reducing substances of interest for analytical purposes.

Creating Oxidase-Peroxidase Fusion Enzymes as a Toolbox for Cascade Reactions.

A set of bifunctional oxidase-peroxidases has been prepared by fusing four distinct oxidases to a peroxidase. Although such fusion enzymes have not been observed in nature, they could be expressed and purified in good yields. Characterization revealed that the artificial enzymes retained the capability to bind the two required cofactors and were catalytically active as oxidase and peroxidase. Peroxidase fusions of alditol oxidase and chitooligosaccharide oxidase could be used for the selective detection of xylitol and cellobiose with a detection limit in the low-micromolar range. The peroxidase fusions of eugenol oxidase and 5-hydroxymethylfurfural oxidase could be used for dioxygen-driven, one-pot, two-step cascade reactions to convert vanillyl alcohol into divanillin and eugenol into lignin oligomers. The designed oxidase-peroxidase fusions represent attractive biocatalysts that allow efficient biocatalytic cascade oxidations that only require molecular oxygen as an oxidant.

Furfural and glucose can enhance conversion of xylose to xylitol by Candida magnoliae TISTR 5663.

Xylitol production from xylose by the yeast Candida magnoliae TISTR 5663 was enhanced by supplementing the fermentation medium with furfural (300mg/L) and glucose (3g/L with an initial mass ratio of glucose to xylose of 1:10) together under oxygen limiting conditions. In the presence of furfural and glucose, the final concentration of xylitol was unaffected relative to control cultures but the xylitol yield on xylose increased by about 5%. Supplementation of the culture medium with glucose alone at an initial concentration of 3g/L, stimulated the volumetric and specific rates of xylose consumption and the rate of xylitol production from xylose. In a culture medium containing 30g/L xylose, 300mg/L furfural and 3g/L glucose, the volumetric production rate of xylitol was 1.04g/L h and the specific production rate was 0.169g/g h. In the absence of furfural and glucose, the volumetric production rate of xylitol was ∼35% lower and the specific production rate was nearly 30% lower. In view of these results, xylose-containing lignocellulosic hydrolysates contaminated with furfural can be effectively used for producing xylitol by fermentation so long as the glucose-to-xylose mass ratio in the hydrolysate does not exceed 1:10 and the furfural concentration is ≤300mg/L.

Engineering of Corynebacterium glutamicum for xylitol production from lignocellulosic pentose sugars.

Xylitol is a non-fermentable sugar alcohol used as sweetener. Corynebacterium glutamicum ATCC13032 was metabolically engineered for xylitol production from the lignocellulosic pentose sugars xylose and arabinose. Direct conversion of xylose to xylitol was achieved through the heterologous expression of NAD(P)H-dependent xylose reductase (xr) gene from Rhodotorula mucilaginosa. Xylitol synthesis from arabinose was attained through polycistronic expression of l-arabinose isomerase (araA), d-psicose 3 epimerase (dpe) and l-xylulose reductase (lxr) genes from Escherichia coli, Agrobacterium tumefaciens and Mycobacterium smegmatis, respectively. Expression of xr and the synthetic araA-dpe-lxr operon under the control of IPTG-inducible Ptac promoter enabled production of xylitol from both xylose and arabinose in the mineral (CGXII) medium with glucose as carbon source. Additional expression of a pentose transporter (araTF) gene enhanced xylitol production by about four-fold compared to the parent strain. The constructed strain Cg-ax3 produced 6.7±0.4g/L of xylitol in batch fermentations and 31±0.5g/L of xylitol in fed-batch fermentations with a specific productivity of 0.28±0.05g/g cdw/h. The strain Cg-ax3 was also validated for xylitol production from pentose rich, acid pre-treated liquor of sorghum stover (SAPL) and the results were comparable in both SAPL (27±0.3g/L) and mineral medium (31±0.5g/L).

Xylitol Chewing Gums on the Market: Do They Prevent Caries?

PURPOSE: To measure the xylitol content in sugar-free chewing gums available on the market in Gulf Cooperation Council (GCC) countries in the Middle East, in order to identify those products that can provide the recommended daily dose of xylitol for caries prevention (6-7 g). Acid production from chewing gums was also measured in vitro and in vivo. MATERIALS AND METHODS: Twenty-one chewing gums containing xylitol were identified and collected from the GCC market (Kuwait, Bahrain, Qatar, Saudi Arabia, UAE and Oman). Xylitol was extracted and its concentration was analysed using a special enzymatic kit. The pH of extracts was measured during 30-min incubation with Streptococcus mutans. Changes in saliva and plaque pH were noted in four subjects after the consumption of highly concentrated xylitol gums. RESULTS: The xylitol content in grams was clearly mentioned only on one product's label. Twelve products stated the percentage of xylitol (3.5% to 35%). The rest did not specify the amount. The mean measured weight of one piece of gum was 1.67 ± 0.38 g. The mean measured xylitol content/piece was 0.33 ± 0.21 g. Xylitol content was < 0.3 g/ piece in 9 products, 0.3-0.5 g in 7 and > 0.5 g in 5 products. None of the highly concentrated xylitol gums showed a pH drop in vitro or in vivo. One chewing gum, containing xylitol and glucose, resulted in a low pH level (< 5.5) when tested in vitro. CONCLUSION: The majority of xylitol chewing gums sold on the GCC market do not provide the consumers with the recommended daily dose of xylitol for caries prevention. Clear, accurate labeling is recommended.

Supplementation of xylitol-containing chewing gum with probiotics: a double blind, randomised pilot study focusing on saliva flow and saliva properties.

The aim of this study was to investigate the impact of daily chewing, for 12 weeks, of 2 different probiotic gums compared with placebo on saliva flow rate, saliva IgA levels and saliva pH. The intervention study included 54 adult volunteers with hyposalivation in a double-blind, randomised and placebo-controlled design with three parallel groups. Volunteers were randomly assigned to 3 different groups: subjects in group A (n = 19) were given placebo chewing gum, group B (n = 17) received Bifidobacterium animalis ssp. lactis Bb12 (ATCC 27536) and group C (n = 18) received Lactobacillus rhamnosus LGG (ATCC 53103), Bifidobacterium longum 46 (DSM 14583) and Bifidobacterium longum 2C (DSM 14579) gums, during 3 months. Two volunteers from group B left the study for personal reasons leaving 19, 15 and 18 volunteers, respectively, for analyses. Clinical examinations, personal interviews, sialometries and saliva sampling were conducted at baseline and after 1, 2, 3 and 4 months. No statistically significant differences were found between probiotic and placebo groups for any of the parameters analysed. No side effects of probiotic or placebo chewing gums were observed. Chewing gum, with and without probiotics, had a positive impact on salivary flow rate and saliva pH and IgA levels.

Electrochemical oxidation and electroanalytical determination of xylitol at a boron-doped diamond electrode.

Xylitol is a reduced sugar with anticariogenic properties used by insulin-dependent diabetics, and which has attracted great attention of the pharmaceutical, cosmetics, food and dental industries. The detection of xylitol in different matrices is generally based on separation techniques. Alternatively, in this paper, the application of a boron-doped diamond (BDD) electrode allied to differing voltammetric techniques is presented to study the electrochemical behavior of xylitol, and to develop an analytical methodology for its determination in mouthwash. Xylitol undergoes two oxidation steps in an irreversible diffusion-controlled process (D=5.05 × 10(-5)cm(2)s(-1)). Differential pulse voltammetry studies revealed that the oxidation mechanism for peaks P1 (3.4 ≤ pH ≤ 8.0), and P2 (6.0 ≤ pH ≤ 9.0) involves transfer of 1H(+)/1e(-), and 1e(-) alone, respectively. The oxidation process P1 is mediated by the (•)OH generated at the BDD hydrogen-terminated surface. The maximum peak current was obtained at a pH of 7.0, and the electroanalytical method developed, (employing square wave voltammetry) yielded low detection (1.3 × 10(-6) mol L(-1)), and quantification (4.5 × 10(-6) mol L(-1)) limits, associated with good levels of repeatability (4.7%), and reproducibility (5.3%); thus demonstrating the viability of the methodology for detection of xylitol in biological samples containing low concentrations.

A geographical discrimination of Shanxi extra aged vinegars using polyalcohols as the discriminators.

A discrimination method based on polyalcohol determination was developed for authenticity of protected geographical indication (PGI) vinegars-Shanxi extra aged vinegar (SVs) in China. Six polyalcohols in vinegars including erythritol, arabitol, xylitol, inositol, mannitol, and sorbitol were selected as the PGI discriminators. GC/MS was used to analyze the polyalcohols in the SVs, Zhenjiang vinegars (ZVs), Kazuo aged vinegars (KVs), and other non-geographical indication protected vinegars (NVs). SVs can be distinguished from KVs by the chemical markers mannitol and sorbitol, although the production processes for both types of vinegars are similar. Principal component analysis (PCA) was used to distinguish SVs from ZVs and NVs. The differences among the three kinds of vinegars shown by PCA results may be due to the higher erythritol content in SVs, and the inositol and mannitol in ZVs. This study also found that the amount of polyalcohols in Chinese vinegars increases with the acidity value only, regardless of the aging time. The overall results indicated that the polyalcohols can be practicable discriminators for SV discrimination.

Production of xylitol by recombinant microalgae.

Microalgae have received significant attention recently as a potential low-cost host for the production of next-generation biofuels and natural products. Here we show that the chloroplast genome of the eukaryotic green microalga Chlamydomonas reinhardtii can be genetically engineered to produce xylitol through the introduction of a gene encoding a xylose reductase (XR) from the fungi Neurospora crassa. Increased levels of heterologous protein accumulation and xylitol production were achieved by synthesizing the XR gene in the chloroplast codon bias and by driving expression of the codon-optimized XR gene using a 16S/atpA promoter/5'-UTR fusion. These results demonstrate the feasibility of engineering microalgae to produce xylitol, and show the importance of codon optimizing the XR gene and using the 16S/atpA promoter/5'-UTR fusion to express XR in the chloroplast of C. reinhardtii.

NAD⁺-dependent xylitol dehydrogenase (xdhA) and L-arabitol-4-dehydrogenase (ladA) deletion mutants of Aspergillus oryzae for improved xylitol production.

Xylitol dehydrogenase (XDHA) and L-arabitol dehydrogenase (LADA) are two key enzymes in xylan metabolism catalyzing the oxidation of xylitol to D-xylulose and arabitol to L-xylulose, respectively. In Aspergillus oryzae, XDHA and LADA are encoded by xdhA and ladA. We deleted xdhA and ladA and xdhA-ladA to generate mutants with decreased dehydrogenase activities and increased xylitol production. The mutants were constructed by homologous transformation into A. oryzae P4 (∆pyrG) using pyrG as a selectable marker. The xylitol productivity of the mutants was measured using D-xylose as the sole carbohydrate source. xdhA, ladA, and the double-deletion mutant produced, respectively, 12.4 g xylitol/l with a yield of 0.24 g/g D-xylose, 12.4 g/l with a yield of 0.33 g/g D-xylose, and 8.6 g/l at a yield of 0.26 g/g D-xylose.

Construction of an efficient xylose-fermenting diploid Saccharomyces cerevisiae strain through mating of two engineered haploid strains capable of xylose assimilation.

Saccharomyces cerevisiae can be engineered for xylose fermentation through introduction of wild type or mutant genes (XYL1/XYL1 (R276H), XYL2, and XYL3) coding for xylose metabolic enzymes from Scheffersomyces stipitis. The resulting engineered strains, however, often yielded undesirable phenotypes such as slow xylose assimilation and xylitol accumulation. In this study, we performed the mating of two engineered strains that exhibit suboptimal xylose-fermenting phenotypes in order to develop an improved xylose-fermenting diploid strain. Specifically, we obtained two engineered haploid strains (YSX3 and SX3). The YSX3 strain consumed xylose rapidly and produced a lot of xylitol. On the contrary, the SX3 strain consumed xylose slowly with little xylitol production. After converting the mating type of SX3 from alpha to a, the resulting strain (SX3-2) was mated with YSX3 to construct a heterozygous diploid strain (KSM). The KSM strain assimilated xylose (0.25gxyloseh(-1)gcells(-1)) as fast as YSX3 and accumulated a small amount of xylitol (0.03ggxylose(-1)) as low as SX3, resulting in an improved ethanol yield (0.27ggxylose(-1)). We found that the improvement in xylose fermentation by the KSM strain was not because of heterozygosity or genome duplication but because of the complementation of the two xylose-metabolic pathways. This result suggested that mating of suboptimal haploid strains is a promising strategy to develop engineered yeast strains with improved xylose fermenting capability.

Xylitol concentrations in artificial saliva after application of different xylitol dental varnishes.

OBJECTIVE: The present study analyzed xylitol concentrations in artificial saliva over time after application of varnishes containing 10% and 20% xylitol. MATERIAL AND METHODS: Fifteen bovine enamel specimens (8x4 mm) were randomly allocated to 3 groups (n=5/group), according to the type of varnish used: 10% xylitol, 20% xylitol and no xylitol (control). After varnish application (4 mg), specimens were immersed in vials containing 500 µL of artificial saliva. Saliva samples were collected in different times (1, 8, 12, 16, 24, 48 and 72 h) and xylitol concentrations were analyzed. Data were assessed by two-way repeated-measures ANOVA (p<0.05). RESULTS: Colorimetric analysis was not able to detect xylitol in saliva samples of the control group. Salivary xylitol concentrations were significantly higher up to 8 h after application of the 20% xylitol varnish. Thereafter, the 10% xylitol varnish released larger amounts of that polyol in artificial saliva. CONCLUSIONS: Despite the results in short-term, sustained xylitol releases could be obtained when the 10% xylitol varnish was used. These varnishes seem to be viable alternatives to increase salivary xylitol levels, and therefore, should be clinically tested to confirm their effectiveness.

Xylitol concentrations in artificial saliva after application of different xylitol dental varnishes

OBJECTIVE: The present study analyzed xylitol concentrations in artificial saliva over time after application of varnishes containing 10% and 20% xylitol. MATERIAL AND METHODS: Fifteen bovine enamel specimens (8x4 mm) were randomly allocated to 3 groups (n=5/group), according to the type of varnish used: 10% xylitol, 20% xylitol and no xylitol (control). After varnish application (4 mg), specimens were immersed in vials containing 500 µL of artificial saliva. Saliva samples were collected in different times (1, 8, 12, 16, 24, 48 and 72 h) and xylitol concentrations were analyzed. Data were assessed by two-way repeated-measures ANOVA (p<0.05). RESULTS: Colorimetric analysis was not able to detect xylitol in saliva samples of the control group. Salivary xylitol concentrations were significantly higher up to 8 h after application of the 20% xylitol varnish. Thereafter, the 10% xylitol varnish released larger amounts of that polyol in artificial saliva. CONCLUSIONS: Despite the results in short-term, sustained xylitol releases could be obtained when the 10% xylitol varnish was used. These varnishes seem to be viable alternatives to increase salivary xylitol levels, and therefore, should be clinically tested to confirm their effectiveness.

Evaluation of the efficacy of two mouthrinses formulated for the relief of xerostomia of diverse origin in adult subjects.

OBJECTIVE: To evaluate the efficacy of two new mouthrinses in the reduction of xerostomía-associated symptomatology. BACKGROUND: Xerostomia is a common chronic health condition that affects a great number of adults and significantly deteriorates quality of life, such that treatment is necessary. MATERIALS AND METHODS: Sixty-seven adult subjects of both sexes presenting xerostomia of diverse origin were selected. Mouthrinses were tested using a double-blind, randomized, cross-over clinical trial with an intervining wash out period. RESULTS: The 100% of subjects presented sensation of dry mouth, and 86% stated sensation of thick saliva. Burning tongue sensation, need to drink liquids to swallow and the sensation of swallowing difficulty were recorded in more than 50% of the patients. The most frequent pathologies in the sample were depression, arthritis, and arterial hypertension. Results of the clinical tests showed that mouthrinse 1 relieves sensation of dry mouth, need to drink liquids, and swallowing difficulty. In contrast, mouthrinse 2 relieves only latter two symptoms. Both rinses were more effective in relieving xerostomía-associated symptomatology in patients taking 3 or more medicines simultaneously. CONCLUSION: Both mouthrinses were effective in relieving various xerostomia symptoms, could be distributed at a low cost, thereby improving the quality of life of population affected.

Evaluation of sorghum straw hemicellulosic hydrolysate for biotechnological production of xylitol by Candida guilliermondii

A preliminary study on xylitol production by Candida guilliermondii in sorghum straw hemicellulosic hydrolysate was performed. Hydrolysate had high xylose content and inhibitors concentrations did not exceed the commonly found values in other hemicellulosic hydrolysates. The highest xylitol yield (0.44 g/g) and productivity (0.19 g/Lh) were verified after 72 hours.

Near infrared spectroscopy as high-throughput technology for screening of xylose-fermenting recombinant Saccharomyces cerevisiae strains.

Recently, genetic engineering efforts have been made to develop recombinant Saccharomyces cerevisiae strains able to utilize xylose, an inexpensive and abundant carbon source. However, their construction and selection processes are limited by the speed and expenses of the existing testing methods, thus a rapid and equally precise method will significantly increase the number of tested strains. Here, near infrared (NIR) spectroscopy is proposed as a successful alternative method for screening recombinant xylose-fermenting S. cerevisiae. Supernatant samples of fermentation solutions from one diploid and three haploid recombinant strains were collected along the fermentation process. NIR spectra of the diluted supernatant provided effective differentiation of strains consistent with their phenotypic and genotypic features. This result could be used as a feedback for multicomponent analysis, in order to develop regression model for quantification of consumed glucose and xylose, produced ethanol, glycerol, and xylitol. Robust partial least-squares regression models with high prediction accuracy that are effective with any strain were achieved for all components when the modeling was performed with combined data of all strains, achieving 0.21-1.49 g/L of standard error of prediction with calibration, prediction, limit of detection and limit of quantification in the range of 1.0-4.5 and 3.0-13.4 g/L, respectively.

[Terahertz spectroscopic inspection and analysis of xylitol and D-xylose].

In the present paper, THz spectra of xylitol and D-xylose are measured at room temperature in the frequency region of 0.3-2.6 THz. The results show that characteristic absorption peak of D-xylose was found at 1.67, 1.96 and 2.46 THz, and those of xylitol at 1.62, 1.87 and 2.51 THz. At the same time, density functional theory was applied to obtain the structure and vibration frequencies of the single molecules of two samples in THz region. The simulation results reveal that some of the absorption peaks result from the intra-molecular modes, while the others have to be attributed to intermolecular interaction or phonon modes.

Improving downstream processes to recover tartaric acid, tartrate and nutrients from vinasses and formulation of inexpensive fermentative broths for xylitol production.

BACKGROUND: Vinasses, the main liquid wastes from the distillation process of grape marc and wine lees, are acidic effluents with high organic content, including acids, carbohydrates, phenols, and unsaturated compounds with high chemical oxygen demand, biological oxygen demand and solid concentrations. These wastes can be revalued to provide additional benefits when they are employed as feedstock of some compounds including tartaric acid, calcium tartrate and economic nutrients for the elaboration of fermentable broths. RESULT: This study attempts to recover tartaric acid and calcium tartrate from vinasses. All the tartaric acid initially solubilised was recovered in both processes. The residual streams can be successfully employed as economic nutrients for the xylose to xylitol bioconversion, achieving higher global volumetric productivities (Q(P, xylitol) = 0.232 g L(-1) h(-1)) and products yields (Y(xylitol/S) = 0.57 g g(-1)) than fermentations carried out using commercial nutrients (Q(P, xylitol) = 0.193 g L(-1) h(-1) and Y(xylitol/S) = 0.55 g g(-1) respectively). CONCLUSION: Tartaric acid can be recovered from vinasses in the form of tartaric acid crystals and calcium tartrate. The residual streams generated in the process can be used as economic nutrients for the production of xylitol by D. hansenii.