Sweet Properties Research Articles

Improving organoleptic and antioxidant properties by inhibition of novel miRstv_7 to target key genes of steviol glycosides biosynthetic pathway in Stevia rebaudiana Bertoni.

Stevioside (5-10%) and rebaudioside-A (2-4%) are well-characterized diterpene glycosides found in leaves of Stevia rebaudiana known to have natural sweetening properties with zero glycaemic index. Stevioside has after-taste bitterness, whereas rebaudioside-A is sweet in taste. The ratio of rebaudioside-A to stevioside needs to be changed in order to increase the effectiveness and palatability of this natural sweetener. Plant-specific miRNAs play a significant role in the regulation of metabolic pathways for the biosynthesis of economically important secondary metabolites. In this study inhibition of miRNA through antisense technology was employed to antagonize the repressive action of miRstv_7 on its target mRNAs involved in the steviol glycosides (SGs) biosynthesis pathway. In transgenic plants expressing anti-miRstv_7, reduced expression level of endogenous miRstv_7 was observed than the non-transformed plants. As a result, enhanced expression of target genes, viz. KO (Kaurene oxidase), KAH (Kaurenoic acid-13-hydroxylase), and UGT76G1 (UDP-glycosyltransferase 76G1) led to a significant increase in the rebaudioside-A to stevioside ratio. Furthermore, metabolome analysis revealed a significant increase in total steviol glycosides content as well as total flavonoids content. Thus, our study can be utilized to generate more palatable varieties of Stevia with improved nutraceutical values including better organoleptic and antioxidant properties.

Formulation of mouth rinse from natural plant\'s leaf extract and evaluation of antibacterial activity

Herbal liquid formulations are the preparation for oral health related issues like toothache, swelling, redness, bacterial or fungal infection in mouth, tooth decay, bleeding gums, weakened gums, etc. Such preparation also improves gums strength, removing bad breath and give fresh feel during good start of the day. Dentists generally use such preparations as antimicrobials before or after oral surgery to sanitize the surface of affected gums and teeth to avoid further contamination. Herbs like Tulsi, Clove, Mint, Ginger etc., are generally used either alone or in combination in herbal mouth-wash preparations which also render antibacterial activities. The other herbs like Eucalyptus and Liquorices have been reported to possess antibacterial, anti-oxidant, aromatic, anti- inflammatory and sweetening properties. In the present work, the research continues with formulation and evaluation of a herbal mouth rinse by using a combination of selected herbal extracts of Tulsi, Bael, Eucalyptus leaves and Liquorices rhizome for their antimicrobial activity against S. aureus using agar well diffusion plate technique. It was found that the formulated herbal mouth rinse or preparations gave satisfactory results in controlling the microorganism. Different physicochemical tests of prepared preparations were performed to figure out their pH, phase separation, homogeneity and scent.,

Tongue-on-a-Chip: Parallel Recording of Sweet and Bitter Receptor Responses to Sequential Injections of Pure and Mixed Sweeteners.

A microfluidic tongue-on-a-chip platform has been evaluated relative to the known sensory properties of various sweeteners. Analogous metrics of typical sensory features reported by human panels such as sweet taste thresholds, onset, and lingering, as well as bitter off-flavor and blocking interactions were deduced from the taste receptor activation curves and then compared. To this end, a flow cell containing a receptor cell array bearing the sweet and six bitter taste receptors was transiently exposed to pure and mixed sweetener samples. The sample concentration gradient across time was separately characterized by the injection of fluorescein dye. Subsequently, cellular calcium responses to different doses of advantame, aspartame, saccharine, and sucrose were overlaid with the concentration gradient. Parameters describing the response kinetics compared to the gradient were quantified. Advantame at 15 μM recorded a significantly faster sweetness onset of 5 ± 2 s and a longer lingering time of 39 s relative to sucrose at 100 mM with an onset of 13 ± 2 s and a lingering time of 6 s. Saccharine was shown to activate the bitter receptors TAS2R8, TAS2R31, and TAS2R43, confirming its known off-flavor, whereas addition of cyclamate reduced or blocked this saccharine bitter response. The potential of using this tongue-on-a-chip to bridge the gap with in vitro assays and taste panels is discussed.

D-Tagatose: A Rare Sugar with Functional Properties and Antimicrobial Potential against Oral Species.

Carbohydrates have a dietary role, but excessive consumption of high-calorie sugars can contribute to an increased incidence of metabolic diseases and dental caries. Recently, carbohydrates with sweetening properties and low caloric value, such as D-tagatose, have been investigated as alternative sugars. D-tagatose is a rare sugar that has nutritional and functional properties of great interest for health. This literature review presents an approach to the biological effects of D-tagatose, emphasizing its benefits for oral health. Studies report that D-tagatose has antioxidant and prebiotic effects, low digestibility, reduced glycemic and insulinemic responses, and the potential to improve the lipid profile, constituting an alternative for diabetes mellitus and obesity. It can also be observed that D-tagatose has an antioxidant action, favoring the elimination of free radicals and, consequently, causing a reduction in cellular oxidative stress. Furthermore, it also has antibacterial potential against oral species. Regarding oral health, studies have shown that D-tagatose efficiently reversed bacterial coaggregations, including periodontopathogenic species, and impaired the activity and growth of cariogenic bacteria, such as S. mutans. D-tagatose significantly inhibited biofilm formation, pH decrease and insoluble glucan synthesis in S. mutans cultures. Salivary S. mutans counts were also significantly reduced by the consumption of chewing gum containing D-tagatose and xylitol. In addition, there is evidence that tagatose is effective as an air-polishing powder for biofilm decontamination. The literature indicates that D-tagatose can contribute to the prevention of systemic diseases, also constituting a promising agent to improve oral health.

Assessment of Knowledge and Perceptions of Pakistani Adults about Non-nutritive Sweeteners

Non-nutritive sweeteners are used as a substitute for sugar and have strong sweetening properties. They can be helpful in weight management, diabetes, and other insulin sensitivity-related metabolic disorders. Objective: This survey intended to analyze the knowledge and risk perceptions related to the safety and benefits of Non-nutritive sweeteners in a population of Pakistani adults. The impact of knowledge dissemination on the consumption of Non-nutritive sweeteners was also assessed. Methods: An online survey was conducted, and 680 responses were received. Results: Results indicated that 55.7% reported Non-nutritive sweeteners consumption, while 44.3% denied any usage. Only 27.4% of respondents showed trust in regulatory bodies while only 26.2% had any idea about the laws surrounding their use. The second part of the study aimed to examine the effect of knowledge dissemination on Non-nutritive sweeteners consumption, but the result showed that the participants were still not convinced about the safety levels of Non-nutritive sweeteners (p < 0.05). The only statement that participants were persuaded by was that Non-nutritive sweeteners does not pose any risk of cancer. The main reason for consumption was attributed to the low caloric properties of Non-nutritive sweeteners. Conclusions: The results showed that effective communication by regulatory authorities and health professionals via the internet, social media and leaflets can be beneficial in educating the public about Non-nutritive sweeteners. The role of health care professionals is also important to assure the public of the safety of Non-nutritive sweeteners.

SWEETENERS: CLASSIFICATION, PROPERTIES, APPLICATION IN THE TECHNOLOGY OF SOFT DRINKS

Due to healthy eating trends, the needs of diabetics, and economic advantages, the production of sweeteners, their range, and the range of beverages containing them are constantly expanding. At the same time, there are difficulties associated with the necessary selection of sweetening agents to solve specific problems. The data of modern scientific literature on the technological aspects of the use of sweeteners in the production of soft drinks are summarized and their choice for obtaining drinks of the corresponding functional direction is substantiated. All sweeteners can be divided into six groups: sugars, sweeteners (sweet alcohols), synthetic sweeteners, natural sweeteners, natural sugary products, and sugary products derived from starch or sugar. The main properties of various sweeteners are compared: sweetness factor, caloric content, glycemic index. The potential adverse effects that may occur when consuming beverages prepared with their use are analyzed. Natural sugary products are generally less sweet than sugar, while artificial sweeteners have a higher sweetness than sucrose. However, the risks and disadvantages of synthetic sweeteners outweigh the benefits of their use. In this regard, it is advisable to reduce or completely eliminate the consumption of food products containing sweeteners from the human diet. On the other hand, natural sources of sweeteners should be used to eliminate the negative effects associated with sugar consumption. When choosing sweeteners for functional beverages, many criteria are taken into account: sweetness factor, caloric content, effect on blood insulin levels (glycemic index), effect on the human digestive system, effect on dental health, and allowable daily intake. For the widespread introduction of natural sweeteners into beverage formulations, detailed research into how they are processed and used on an industrial scale is required.

Sensory profiling of natural sweeteners and sucrose-sweetener binary mixtures.

Overconsumption of added sugars is associated with higher incidences of obesity, type II diabetes, and cardiovascular disease. Alternative sweeteners have long been relied on as a strategy to reduce consumption of added sugars; however these alternatives differ notably from sucrose in their sensory properties. Recently, consumers have also been looking to reduce consumption of ingredients deemed "artificial," seeking natural alternatives despite poor definitions of these terms on the whole. Wider knowledge of the sensory properties of natural sweeteners would greatly aid in this goal. Descriptive analysis and time-intensity scaling were used to characterize the temporal profile and off-flavors of allulose, erythritol, rebaudioside (Reb) A, Reb D, Reb M, monk fruit, and thaumatin, as compared to sucrose. Further, each was blended to reduce sucrose by 50% and 75% in binary mixtures. Where significant off-flavors were frequently reported with sweeteners, when delivered in binary mixtures for partial sugar reduction, these were much mitigated, while also bringing temporal profiles closer to that of sucrose. This suggests that partial sugar reduction may be an effective way of reducing caloric intake while not compromising sensory experience. PRACTICAL APPLICATION: The use of both descriptive analysis and time-intensity scaling allows for a more complete understanding of the sensory properties of natural alternative sweeteners. Understanding their sensory deficits and ways to improve these sweeteners plays a critical role in creating healthier products that will be accepted by consumers.

EPR Investigation of Temporal and Thermal Stability of Irradiated Sweeteners

Abstract Electron paramagnetic resonance was used to study the dosimetric properties of commercial sweeteners (sucrose, saccharin, and stevia). The results concluded that sugar has dosimetric properties of interest, which makes it suitable for dose reconstruction, emergency response, and nuclear forensics applications. The radiation dose response was investigated by irradiating samples up to 10 Gy and found to be linear. The post-irradiation stability of samples was observed to be useful for the intended applications. The results showed that the post-irradiation intensities vary from one sample to another, with the general trend demonstrating a small increase in intensities shortly after irradiation followed by an approximately constant leveling out. Finally, the effect of isochronal annealing was studied by heating samples to various temperatures. The results showed an overall stable behavior of the signal below melting temperature.

Biological production of xylitol by using nonconventional microbial strains.

Xylitol (C5H12O5), an amorphous sugar alcohol of crystalline texture has received great interest on the global market due to its numerous applications in different industries. In addition to its high anticariogenic and sweetening properties, characteristics such as high solubility, stability and low glycemic index confer xylitol its fame in the food and odontological industries. Moreover, it also serves as a building-block in the production of polymers. As a result of the harmful effects of the chemical production of xylitol, the biotechnological means of producing this polyol have evolved over the decades. In contrast to the high consumption of energy, long periods of purification, specialized equipment and high production cost encountered during its chemical synthesis, the biotechnological production of xylitol offers advantages both to the economy and the environment. Non-Saccharomyces yeast strains, also termed as nonconventional, possess the inherent capacity to utilize D-xylose as a sole carbon source, unlike Saccharomyces species.

Is the Use of Artificial Sweeteners Beneficial for Patients with Diabetes Mellitus? The Advantages and Disadvantages of Artificial Sweeteners.

Artificial sweeteners have been developed as substitutes for sugar. Sucralose, acesulfame K (ACE K), aspartame, and saccharin are artificial sweeteners. Previously, artificial sweeteners were thought to be effective in treating obesity and diabetes. Human meta-analyses have reported that artificial sweeteners have no effect on body weight or glycemic control. However, recent studies have shown that artificial sweeteners affect glucose absorption in the intestinal tract as well as insulin and incretin secretion in humans and animals. Moreover, artificial sweeteners alter the composition of the microbiota and worsen the glycemic control owing to changes in the gut microbiota. The early intake of ACE K was also shown to suppress the taste response to sugar. Furthermore, a large cohort study showed that high artificial sweetener intake was associated with all-cause mortality, cardiovascular risk, coronary artery disease risk, cerebrovascular risk, and cancer risk. The role of artificial sweeteners in the treatment of diabetes and obesity should be reconsidered, and the replacement of sugar with artificial sweeteners in patients will require the long-term tracking of not only intake but also changes in blood glucose and weight as well as future guidance based on gut bacteria data. To utilize the beneficial properties of artificial sweeteners in treatment, further studies are needed.

The Effects of Silveroxide on mRNA Level of Key Genes Involved In the Biosynthesis of Rebaudioside-A in Stevia Rebaudiana

Stevia rebaudiana bertoni is a plant with sweetening properties. This medicinal plant is perennial and from Asteraceae family. Its leaves contain glycoside compounds of a sugar part and non-sugar sectors. One of the glycosides compounds is Rebaudioside¬A which has a greater importance in market. Several key regulating genes including copalyl diphosphate synthase (CPPS) (AF034545.1), geranylgeranyl diphosphate synthase (GGDPS) (DQ432013.3), (E)-4-hydroxy-3-methylbut-2-enyl diphosphate synthase (HDS) (FJ755689.1), UDP glucosyltranserase 85C2(UGT85C2)(AY345978.1), UDPglucosyltranserase–74G1 (UGT74G1) (AY345982.1) and UDP glucosyltranserase–76G1 (UGT76G1) (KC631816.1) are involved in the biosynthesis Rebaudioside A. This experiment was conducted to evaluate the effect of silver oxide Ag2O on the mRNA level of these genes in the stevia rebaudiana. The experiments repeated 3 times and with concentrations of 50, 100 and 200 µM. Increasing concentrations of 50 micromoles of silver oxide up to 100 micromoles leads to an increase in the expression levels of all the studied genes. Also according to the expression profile of these genes and the results of HPLC there is a significant increase on the expression level of the genes and production of Rebaudioside¬A under Ag2O treatment. In general, it was found that increasing the concentration of Ag2O can lead to an increase in the level of mRNA for the chosen genes. On the other hand, the low expression of the genes studied under control conditions (No Treatment), compared to the treatment with Ag2O, revealed that the treatment can lead to higher sweetener glycoside components in the Stevia leaves. The physiological assay showed that Ag2O treatment in concentrations of 100 and 200 µM have more positive effect on chlorophyll, protein, carbohydrates and carotenoids in Stevia.

TECHNOLOGICAL ASPECTS OF DEVELOPMENT CONFECTIONERY
 PRODUCTS’ WITH POLYOLS

The article substantiates the relevance of the development of confectionery products with a reduced content of easily digestible carbohydrates and content of calories’, including those suitable for diabetic nutrition. A comparative analysis of the technological and physiological properties of sweeteners (polyols) was carried out and showed the prospects of using sorbitol, xylitol, maltitol and maltitol syrup for the manufacture of musli-bars without added sugar, including those suitable for diabetic nutrition. The processes of heat treatment of syrups with sweeteners are studied, regression equations are selected that allow determining the dry matter content in the syrup at a certain temperature or setting the temperature to which it is necessary to boil the syrup to achieve the required dry matter content. The influence of sweeteners on the dynamic viscosity of syrups and the strength of bars is studied. The determination of the mass fraction of total sugar (in terms as sucrose) was carried out, according to the results of which the developed products were classified as specialized products of diabetic nutrition. The complex analysis allowed to determine the optimal sweetener and, based on the results obtained, developed recipes for musli-bars without added sugar: «Cereals with raspberries», «Cereals with hazelnuts», «Cereals with blueberries».

Genotypic characterization and steviol glycoside quantification in a population of Stevia rebaudiana Bertoni from Paraguay

Stevia rebaudiana (Bertoni) Bertoni is a widely grown species in various regions of the world, mainly due to its sweetening properties attributed to steviol glycosides. Despite the fact that Paraguay is the center of origin of S. rebaudiana, genetic characterization of local genotypes has not been studied. Considering that accumulation of steviol glycosides is a complex trait, molecular breeding could be an effective method for its improvement. Therefore, the identification of molecular markers associated with steviol glycoside accumulation is important. The aim of this study was to assess the genetic relationship among eight advanced lines of S. rebaudiana and two varieties selected from local germoplasm and quantify their steviol glycoside content. The stevioside and rebaudioside A content in methanolic extract was determined by high-performance liquid chromatography (HPLC), and the molecular characterization of the ten genotypes of S. rebaudiana was performed using SSR and ISSR markers. A wide range of variability was observed for the metabolites of interest under greenhouse conditions. The variety Eirete presented highest stevioside and rebausiode A content, followed by the variety Katupyry. One of the advanced line presented both metabolite content similar to that of Katupyry. Genotyping of these lines showed two main clusters. Cluster I contained the both varieties and advanced lines with higher stevioside and rebaudioside A content. Our results suggest that S. rebaudiana lines with genetic profile similar to that of cluster I, determined mainly by genotype at the markers SUGMS 35 and ISSR 47, might present higher stevioside and rebaudioside A content.

Trichoderma asperellum, un inoculante para la producción de glucósidos de esteviol de plantas de Stevia rebaudiana Bertoni micropagadas en bioreactor de inmersión temporal

Stevia rebaudiana is a plant that synthesizes steviol glycosides, which are compounds with sweetening properties. The aim of this work was to evaluate the growth-promoting effect of a micropropagation system in a Temporary Immersion Bioreactor (TIB) and the inoculation with Trichoderma asperellum on the S. rebaudiana plants, and to determine their effect on the production of steviol glycosides and phenolic compounds. S. rebaudiana plants with intact roots were obtained using a TIB with Murashigue and Skoog medium and 0.37 mg L-1 indole butyric acid, and subsequent the plants were inoculated with spores of T. asperellum (4 x 104 spores mL-1). The growth of plants inoculated with the fungus was significantly larger than the plants uninoculated (control). The plants inoculated produced 3 times more steviol glycosides than the plants uninoculated (control); while, the content of phenolic compounds was similar. These results encourage the possibility of using a TIB and T. asperellum for the propagation and growth promotion of S. rebaudiana plants with high content of steviol glycosides.

Biotechnological Production of Natural Calorie Free Steviol Glycosides in Stevia rebaudiana: An Update on Current Scenario

Stevia rebaudiana is a vital medicinal plant of the genus Stevia and family Asteraceae. It is commonly used as a natural sweetener plant and its products are 300 times sweeter than the commonly used sugarcane. The sweetening potential is due to the presence of calorie-free steviol glycosides (SGs). The plant species has been extensively profiled to identify steviol glycosides (SGs) with intensity sweetening properties. However, the limited production of plant material is not fulfilling the higher market demand worldwide. Researchers are working worldwide to enhance the production of important SGs through the intervention of different biotechnological approaches in S. rebaudiana. In this review, the research work conducted in the last twenty years, on the different aspects of biotechnology to enhance the production of SGs has been precisely reviewed. Biotechnological methods such as micropropagation, callus and cell cultures, elicitation and the metabolomics and transcriptomic elucidation of the biosynthetic metabolic pathways for the production of steviol glycosides have been concisely reviewed and discussed.

Sensory Influence of Sweetener Addition on Traditional and Decaffeinated Espresso.

Several factors have led to an increase in the consumption of sweeteners in substitution of sucrose. Studies on the behavior and the sensory properties of sweeteners are relevant, once they provide knowledge about both the adequate sweetener concentration with a sweetness equivalence to a sucrose-sweetened product and the possible sensory changes of the product. The addition of stevia with different rebaudioside A concentrations and sucralose to traditional and decaffeinated espresso coffee was studied, using the just-about-right scale and magnitude estimation method, to determine the ideal sweetness and the acceptance of the samples. The effect of the intensity of sensory attributes sweet taste, bitter taste, coffee flavor, and body in the acceptance was evaluated by penalty analysis. Decaffeinated presented proportionally lower sucrose concentration and sweetness equivalence than the traditional samples. Stevia concentrations were similar, despite the different rebaudioside A concentrations, for both traditional and decaffeinated samples, and rebaudioside A levels from stevia in espresso have no differences in sweetness intensity. Sucralose was the most intense sweetener in espresso. Although no differences were observed in the acceptance test in relation to appearance, aroma, and texture among the samples, the internal preference map showed segmentation of consumers with respect to the acceptability. This segmentation is more related to the type of sample than the added sweetener. Penalty analysis demonstrated that the most penalizing sensory characteristics were "coffee flavor" and "sweet," leading to a significant decrease in the acceptability of the samples. PRACTICAL APPLICATION: Conclusions obtained are important source of knowledge for the coffee industry, in the development and manufacture of beverages with coffee. The present findings can help to understand the behavior and the sensory properties of sweeteners. They provide knowledge about sensory perception of sweet and bitter tastes, and the factors that influence this perception and the sensory profile of the samples, once the behavior of sweeteners varies according to the product to which they are added.

The choice of intense sweetener in the composition of medicated chewing gum under development

Considering the simplicity and ease of use, in recent years, more and more attention deserves medicated chewing gum (MCG), which plays the role of oral drug delivery system. Since this product remains in the oral cavity for a longer time than other oral medicines, the taste is one of the important features of the MCG. It is known, that one of the ways to correct and mask the taste of medicines is the addition of intense sweeteners, which not only affect the taste characteristics of the ready product, but also can influence the physic-chemical and technological properties of the active components.
 The aim of this work was the selection of the optimal intensive sweetener in the developed dental MCG with lysozyme hydrochloride and ascorbic acid.
 As natural flavourers, we studied natural and synthetic intensive sweeteners: potassium acesulfame, aspartame, sodium cyclamate, sodium saccharin, stevia and sucralose. The choice of flavouring agents was carried out using organoleptic methods for evaluating the taste with the help of numerical indexes by A. I. Tentsova and use of alphabetic and numerical indexes by I. A. Yegorov, and also by studying the crystallographic properties of intense sweeteners and their mixtures with active pharmaceutical ingredients.
 According to the obtained results, all compositions, except for the sample with sodium saccharin, had a corrective property and had a similar sweet-sour taste. However, not all of them had a long sweet aftertaste, which is very important for this dosage form. The highest numerical indices were samples of MCG with sodium cyclamate, stevia and sucralose. By conducting a microscopic analysis of mixtures of active pharmaceutical ingredients with the investigated intense sweeteners were predicted possible methods of obtaining the developed solid dosage form – the method of direct compression or the use of preliminary granulation. Taking into account the complex of the obtained results, sucralose has the best correcting and physic-chemical characteristics of all the investigated intense sweeteners.

De novo in vitro shoot morphogenesis from shoot tip-induced callus cultures of Gymnema sylvestre (Retz.) R.Br. ex Sm

BackgroundGymnema sylvestre is a medicinal woody perennial vine known for its sweetening properties and anti-diabetic therapeutic uses in the modern and traditional medicines. Its over-exploitation for the therapeutic uses and to meet the demand of pharmaceutical industry in raw materials supply for the production of anti-diabetic drugs has led to considerable decline in its natural population.ResultsAn efficient system of shoot bud sprouting from nodal segment explants and indirect plant regeneration from apical meristem-induced callus cultures of G. sylvestre have been developed on Murashige and Skoog (MS) medium amended with concentrations of cytokinins. Of the three growth regulators tested, N6-benzylaminopurine (BAP) was the most efficient and 2.0 mg L−1 gave the best shoot formation efficiency. This was followed by thidiazuron (TDZ) and kinetin (Kin) but, most of the TDZ-induced micro shoots showed stunted growth. Multiple shoot formation was observed on medium amended with BAP or TDZ at higher concentrations. The produced micro shoots were rooted on half strength MS medium amended with auxins and rooted plantlets acclimatized with 87% survival of the regenerates.ConclusionsThe developed regeneration system can be exploited for genetic transformation studies, particularly when aimed at producing its high yielding cell lines for the anti-diabetic phytochemicals. It also offers opportunities for exploring the expression of totipotency in the anti-diabetic perennial vine.

Identification, characterization of two NADPH-dependent erythrose reductases in the yeast Yarrowia lipolytica and improvement of erythritol productivity using metabolic engineering

BackgroundErythritol is a four-carbon sugar alcohol with sweetening properties that is used by the agro-food industry as a food additive. In the yeast Yarrowia lipolytica, the last step of erythritol synthesis involves the reduction of erythrose by specific erythrose reductase(s). In the earlier report, an erythrose reductase gene (YALI0F18590g) from erythritol-producing yeast Y. lipolytica MK1 was identified (Janek et al. in Microb Cell Fact 16:118, 2017). However, deletion of the gene in Y. lipolytica MK1 only resulted in some lower erythritol production but the erythritol synthesis process was still maintained, indicating that other erythrose reductase gene(s) might exist in the genome of Y. lipolytica.ResultsIn this study, we have isolated genes g141.t1 (YALI0D07634g) and g3023.t1 (YALI0C13508g) encoding two novel erythrose reductases (ER). The biochemical characterization of the purified enzymes showed that they have a strong affinity for erythrose. Deletion of the two ER genes plus g801.t1 (YALI0F18590g) did not prevent erythritol synthesis, suggesting that other ER or ER-like enzymes remain to be discovered in this yeast. Overexpression of the newly isolated two genes (ER10 or ER25) led to an average 14.7% higher erythritol yield and 31.2% higher productivity compared to the wild-type strain. Finally, engineering NADPH cofactor metabolism by overexpression of genes ZWF1 and GND1 encoding glucose-6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase, respectively, allowed a 23.5% higher erythritol yield and 50% higher productivity compared to the wild-type strain. The best of our constructed strains produced an erythritol titer of 190 g/L in baffled flasks using glucose as main carbon source.ConclusionsOur results highlight that in the Y. lipolytica genome several genes encode enzymes able to reduce erythrose into erythritol. The catalytic properties of these enzymes and their cofactor dependency are different from that of already known erythrose reductase of Y. lipolytica. Constitutive expression of the newly isolated genes and engineering of NADPH cofactor metabolism led to an increase in erythritol titer. Development of fermentation strategies will allow further improvement of this productivity in the future.

Quantitative comparison of adsorption and desorption of commonly used sweeteners in the oral cavity

Adsorption-desorption properties of different sweeteners in the oral cavity were evaluated using high performance liquid chromatography-based methodology. Three low calorie artificial sweeteners (aspartame, acesulfame potassium and sucralose), one steviol glycoside (rebaudioside A), and high fructose corn syrup (HFCS) were examined and compared with sucrose at pH 3 and 7 in a model beverage matrix. Results indicated that HFCS had the highest adsorption in the oral cavity, followed by rebaudioside A and the artificial sweeteners. The physicochemical interaction between sweeteners and salivary proteins did not affect the adsorption properties significantly as validated from a series of characterization techniques.