XYLITOL


Xylitol = Xylit= E967

CAS NO.:87-99-0
EC NO.:201-788-0
Synonym:Xylit
Formula:C5H12O5
Mol. weight:152.15


IUPAC name: meso-Xylitol
Preferred IUPAC name: (2R,3R,4S)-Pentane-1,2,3,4,5-pentol
Other names: (2R,3R,4S)-Pentane-1,2,3,4,5-pentaol 
1,2,3,4,5-Pentahydroxypentane
Xylite

Xylitol is used as a bulk sweetener, mainly in noncariogenic confectionery and oral hygiene preparations (toothpaste and mouthwash), and less frequently in dietetic foods (food products for diabetics), pharmaceutical preparations (tablets, throat lozenges, multivitamin tablets, cough syrup), and solutions for parenteral nutrition.


Xylitol E967 (CAS No.:87-99-0) is a white or almost white crystalline powder or crystal, odorless, easily soluble in water, and slightly soluble in ethanol and methanol. 
It is a polyhydric alcohol, a natural sugar substitute, made by the hydrolysis of xylan-containing plants (birch) into xylose. 
Depending on the concentration, xylitol is similar or slightly sweeter than sucrose and does not cause caries. 
Xylitol dissolves quickly in water and has a negative solution heat, so the substance cools saliva, which brings a cool feeling, which is ideal in certain foods (especially beverages). It is very suitable for chewing gum, throat lozenges, and chocolate.


Xylitol is a food additive permitted for direct addition to food for human consumption, as long as 
1) the quantity of the substance added to food does not exceed the amount reasonably required to accomplish its intended physical, nutritive, or other technical effect in food, and 
2) any substance intended for use in or on food is of appropriate food grade and is prepared and handled as a food ingredient.

Xylitol is a naturally occurring substance that is widely used as a sugar substitute. 
Chemically, it is a sugar alcohol, and is found naturally in berries, plums, corn, oats, mushrooms, lettuce, trees, and some other fruits.

Commercially, most xylitol is extracted from corn fiber or birch trees. 
Although it has been used as a sugar substitute for decades, its popularity has increased dramatically in the last decade due to its low glycemic index and dental plaque fighting properties.

Xylitol provides sweetness and a cooling effect to confectionary products such as chewing gum, coatings, chewy sweets and marshmallow.  
Xylitol provides a variety of functional properties including oral health, blood glucose management, sweetness and calorie reduction. 

Dental plaque, a sticky bacterial film that develops on dental enamel, reoccurs after every meal. 
Those microorganisms feed on sugar fermentation, produced by destructive acids attacking tooth enamel.
Xylitol does not produce acids or cause tooth decay, as the oral bacteria do not metabolize it. 

Xylitol is a chemical categorized as a polyalcohol or sugar alcohol.
Xylitol is a chemical categorized as a polyalcohol or sugar alcohol (alditol). 
Xylitol has the formula (CHOH)3(CH2OH)2 and is an achiral isomer of pentane-1,2,3,4,5-pentol. 
Xylitol is used as a diabetic sweetener which is roughly as sweet as sucrose with 33% fewer calories. 
Unlike other natural or synthetic sweeteners, xylitol is actively beneficial for dental health by reducing caries to a third in regular

Xylitol is commonly used as an artificial sweetener. It is as sweet as sucrose and is noncariogenic. Xylitol is ordinarily used in chewing gum.

Xylitol is a five-carbon sugar alcohol derived from xylose by reduction of the carbonyl group. 
Xylitol is produced by hydrogenation of xylose, which converts the sugar (an aldehyde) into a primary alcohol.


Xylitol is an organic compound with the formula (CHOH)3(CH2OH)2. 
This achiral species is one of three isomers of 1,2,3,4,5-pentapentanol. 
This sugar alcohol is used as a naturally occurring sugar substitute found in the fibres of many fruits and vegetables, including various berries, corn husks, oats, and mushrooms. 
Xylitol can be extracted from corn fibre, birch, raspberries, plums, and corn. Xylitol is roughly as sweet as sucrose with only two-thirds the food energy. 
Xylitol was first derived from Birch trees in Finland in the 20th century and was first popularized in Europe as a safe sweetener for people with diabetes that would not impact insulin levels. Today, commonly hardwood and maize sources are used as raw materials.

Where is xylitol found?
Xylitol is manufactured into a white powder that looks and tastes similar to sugar. In many countries it has been approved for use in oral care products, pharmaceuticals, and as a food additive. Over recent years, the number and types of products that contain xylitol has greatly increased. Example products include sugar-free gum, candies, breath mints, baked goods, peanut butter, pudding snacks, cough syrup, chewable or gummy vitamins, and supplements or over the counter medications, mouthwash, and toothpaste. Xylitol is also showing up in over-the-counter nasal sprays, skin care products, laxatives, digestive aids, allergy medicines, dry mouth lozenges, sleep supplements, as well as prescription human medications, especially those formulated as quick dissolve tablets or liquids.

Why is xylitol increasing in popularity and use?
Xylitol has the same sweetness as sucrose but contains only about two-thirds the calories. As a sugar substitute, it is lower on the glycemic index, a scale that ranks carbohydrate-rich foods by how much they raise blood sugar levels, compared to glucose. Being lower on the glycemic index makes xylitol useful for diabetics or people on low carbohydrate diets.

With respect to oral health, research has shown that xylitol helps reduce the formation of plaque, inhibits dental cavities, and stimulates the production of saliva.

Functions of Xylitol: 
flavoring agent        
humectant        
humectant        
humectant / skin conditioning        
nutritive sweetener

Xylitol is a coating and filler excipient. 
Xylitol is is a non-cariogenic and non-acidogenic sugar-free sweetener that is used in pharmaceutical and nutraceutical oral dosage forms.

CAS Number: 87-99-0 
E number: E967 

Xylitol is used as a sugar substitute in such manufactured products as drugs, dietary supplements, confections, toothpaste, and chewing gum, but is not a common household sweetener.

KEYWORDS:
Xylitol, Xylit,  E967, 87-99-0, 201-788-0, (2R 3R 4S)-Pentane-1 2 3 4 5-pentol, (2R 3R 4S)-Pentane-1 2 3 4 5-pentaol, 1 2 3 4 5-Pentahydroxypentane , flavoring agent , humectant        

Properties of Xylitol
Chemical formula: C5H12O5
Linear Formula: HOCH2[CH(OH)]3CH2OH
Molar mass: 152.146 g·mol−1
Density: 1.52 g/cm3
Melting point: 92 to 96 °C 
Boiling point: 345.39 °C 
Solubility in water: ~100 g/L

Xylitol is a pentitol (five-carbon sugar alcohol) having meso-configuration, being derived from xylose by reduction of the carbonyl group. 
It has a role as a sweetening agent, an allergen, a hapten, a human metabolite, an algal metabolite, a Saccharomyces cerevisiae metabolite and a mouse metabolite.

Xylitol is mainly composed of D-xylitol. The part which is not D-xylitol is composed of related substances such as L-arabinitol, galactitol, mannitol, sorbitol

Xylitol is a naturally occurring alcohol found in most plant material, including many fruits and vegetables. It is extracted from birch wood to make medicine.

Xylitol is widely used as a sugar substitute and in "sugar-free" chewing gums, mints, and other candies. 
However, sorbitol is the most commonly used sweetener in sugarless gums because it is less expensive than xylitol and easier to make into commercial products.

People use xylitol to prevent cavities. 
It is also used to prevent tooth plaque and ear infection (otitis media), and for many other uses.

Pharmacology    
There has been evidence of xylitol in dental hygiene in reducing dental caries disease and also reversing the process of early caries. 
Xylitol increases salivary flow and pH, reduces the levels of _Streptococcus mutans_ in plaque and saliva and reduces the adhesion on the microorganism to the teeth surface. 
_Streptococcus mutans_ is the main target plaque microorganism, but xylitol may potentially have inhibitory actions against several other bacterial species. 
It prevents a shift of the bacterial community towards a more cariogenic microflora in oral environment. 
Oral ingestion of xylitol causes a smaller rise in plasma glucose and insulin concentrations than does the ingestion of glucose in healthy men and diabetics.

Xylitol tastes sweet but, unlike sugar, it is not converted in the mouth to acids that cause tooth decay. 
Xylitol reduces levels of decay-causing bacteria in saliva and also acts against some bacteria that cause ear infections.


Xylitol is a chemical compound with the formula C5H12O5, or HO(CH2)(CHOH)3(CH2)OH; specifically, one particular stereoisomer with that structural formula. 
Xylitol is a colorless or white crystalline solid that is soluble in water. 
Xylitol can be classified as a polyalcohol and a sugar alcohol, specifically an alditol. 
The name derives from Ancient Greek: ξύλον, xyl[on], "wood", with the suffix -itol used to denote sugar alcohols.

Xylitol is used as a food additive and sugar substitute. Its European Union code number is E967.
Replacing sugar with xylitol in food products may promote better dental health, but evidence is lacking on whether xylitol itself prevents dental cavities.


Xylitol is categorized as a sugar alcohol.

Chemically, sugar alcohols combine traits of sugar molecules and alcohol molecules. Their structure allows them to stimulate the taste receptors for sweetness on your tongue.

Xylitol is found in small amounts in many fruits and vegetables and is therefore considered natural. Humans even produce small quantities of it via normal metabolism.

It is a common ingredient in sugar-free chewing gums, candies, mints, diabetes-friendly foods and oral-care products.

Xylitol has a similar sweetness as regular sugar but contains 40% fewer calories:

Table sugar: 4 calories per gram
Xylitol: 2.4 calories per gram

Since xylitol is a refined sweetener, it doesn’t contain any vitamins, minerals or protein. In that sense, it provides only empty calories.

Xylitol can be processed from trees like birch or from a plant fiber called xylan (1Trusted Source).

Even though sugar alcohols are technically carbohydrates, most of them do not raise blood sugar levels and thereby don’t count as net carbs, making them popular sweeteners in low-carb products

 
History
Sugar rationing during World War II led to an interest in sugar substitutes. 
Interest in xylitol and other polyols became intense, leading to their characterization and manufacturing methods.

Structure, production, commerce
Xylitol occurs naturally in small amounts in plums, strawberries, cauliflower, and pumpkin; humans and many other animals make trace amounts during metabolism of carbohydrates.
Unlike most sugar alcohols, xylitol is achiral.
Most other isomers of pentane-1,2,3,4,5-pentol are chiral, but xylitol has a plane of symmetry.

Industrial production starts with lignocellulosic biomass from which xylan is extracted; raw biomass materials include hardwoods, softwoods, and agricultural waste from processing maize, wheat, or rice. 
The xylan polymers can be hydrolyzed into xylose, which is catalytically hydrogenated into xylitol. 
The conversion changes the sugar (xylose, an aldehyde) into the primary alcohol, xylitol. Impurities are then removed.

The processing is often done using standard industrial methods; industrial fermentation involving bacteria, fungi, or yeast, especially Candida tropicalis, are common, but are not as efficient.

According to the US Department of Energy, xylitol production by fermentation from discarded biomass is one of the most valuable renewable chemicals for commerce, forecast to be a US$1.4 billion industry by 2025.


Uses of Xylitol:
Xylitol is used as a sugar substitute in such manufactured products as drugs, dietary supplements, confections, toothpaste, and chewing gum, but is not a common household sweetener.
Xylitol has negligible effects on blood sugar because it is metabolized independently of insulin.
It is approved as a food additive in the United States.

Xylitol is also found as an additive to saline solution for nasal irrigation and has been reported to be effective in improving symptoms of chronic sinusitis.

Food properties of Xylitol:
Nutrition, taste, and cooking
Humans absorb xylitol more slowly than sucrose, and xylitol supplies 40% fewer calories than an equal mass of sucrose.

Xylitol has about the same sweetness as sucrose, but is sweeter than similar compounds like sorbitol and mannitol.

Xylitol is stable enough to be used in baking, but because xylitol and other polyols are heat stable, they do not caramelise as sugars do. 
When used in foods, they lower the freezing point of the mixture.

Xylitol is stable to heat but is marginally hygroscopic. Caramelization can occur only if it is heated for several minutes near ist boiling point.
Milled and specialized granulated grades of xylitol have a tendency to cake and should therefore be used within 9 to 12 months. 
Aqueous xylitol solutions have been reported to be stable, even on prolonged heating and storage.

Sugar Free Sweetener


Applications of Xylitol: 
Confectionery
Chewing-gum
Chewy sweet & marshmallow
Filling & coating

Functional Properties of Xylitol : 
Make it indulgent
Mouthfeel enhancer
Sweetness
Make it better and healthier
Blood glucose management
Sugar-free
Energy management
Oral health
Optimize my formulation
Higher yields
Flowability and viscosity
Ingredient reduction and replacement
Bulking

Other Properties and Benefits
Odorless, white crystalline powder
Sweetening power equal to that of sugar
Very good solubility
Crystallization
Non cariogenic, non-fermentable, toothfriendly
Caloric value: 2.4 kcal /g

Food risks
No serious health risk exists in most humans for normal levels of consumption; The European Food Safety Authority has not set a limit on daily intake of xylitol.
Due to the adverse laxative effect that all polyols have on the digestive system in high doses, xylitol is banned from soft drinks in the European Union. 
Similarly due to a 1985 report, by the E.U. Scientific Committee on Food, stating that "ingesting 50 g a day of xylitol can cause diarrhea", tabletop sweeteners containing xylitol are required to display the warning: "Excessive consumption may induce laxative effects".


Decomposition    
Since xylitol is not utilized by most microoragnisms, products made with xylitol are usually safe from fermentation and microbial spoilage.


Metabolism
Xylitol has 2.4 kilocalories of food energy per gram of xylitol (10 kilojoules per gram) according to U.S. and E.U. food-labeling regulations.
The real value can vary, depending on metabolic factors.

Primarily, the liver metabolizes absorbed xylitol. 
The main metabolic route in humans occurs in cytoplasm, via nonspecific NAD-dependent dehydrogenase (polyol dehydrogenase), which transforms xylitol to D-xylulose. 
Specific xylulokinase phosphorylates it to D-xylulose-5-phosphate. 
This then goes to pentose phosphate pathway for further processing.

About 50% of eaten xylitol is absorbed via the intestines. 
Of the remaining 50% that is not absorbed by the intestines, in humans, 50–75% of the xylitol remaining in the gut is fermented by gut bacteria into short-chain organic acids and gases, which may produce flatulence. 
The remnant unabsorbed xylitol that escapes fermentation is excreted unchanged, mostly in feces; less than 2 g of xylitol out of every 100 g ingested is excreted via urine.

Xylitol ingestion also increases motilin secretion, which may be related to xylitol's ability to cause diarrhea.
The less-digestible but fermentable nature of xylitol also contributes to constipation relieving effects.

Xylitol is a naturally occurring five-carbon sugar alcohol found in most plant material, including many fruits and vegetables. Xylitol-rich plant materials include birch and beechwood. It is widely used as a sugar substitute and in "sugar-free" food products. The effects of xylitol on dental caries have been widely studied, and xylitol is added to some chewing gums and other oral care products to prevent tooth decay and dry mouth. Xylitol is a non-fermentable sugar alcohol by most plaque bacteria, indicating that it cannot be fermented into cariogenic acid end-products. It works by inhibiting the growth of the microorganisms present in plaque and saliva after it accummulates intracellularly into the microorganism. The recommended dose of xylitol for dental caries prevention is 6–10 g/day, and most adults can tolerate 40 g/day without adverse events.

Xylitol is a sugar alcohol, which is a type of carbohydrate and does not actually contain alcohol. Xylitol occurs naturally in small amounts in fibrous fruits and vegetables, trees, corncobs, and even the human body.

Manufacturers use xylitol as a sugar substitute because its sweetness is comparable with that of table sugar but with fewer calories.

Xylitol is a common ingredient in many products, from sugar-free chewing gum to toothpaste. People also use xylitol as a table-top sweetener and in baking.

Xylitol has a similar level of sweetness to sugar but with a fraction of the calories. It is a popular ingredient in a variety of products, including sugar-free gum and toothpaste.

Manufacturers add xylitol to a range of foods, including:

sugar-free candies, such as gum, mints, and gummies
jams and jellies
honey
nut butters, including peanut butter
yogurt
Xylitol is also an ingredient in some dental care products, including:

toothpaste
mouthwash
other fluoride products


Xylitol is an all-natural alternative to sugar. 
The substance derives from the fibres of plants and can be extracted from a variety of vegetation including berries, mushrooms, birch bark and corn husks. 
It’s also produced in our body naturally. 
Its flavour is as sweet as conventional sucrose sugar, but it has only two thirds the calorie count. 
Pure xylitol comes in white crystals and looks and tastes like ordinary granulated sugar. 
It has been traditionally used in chewing gums, toothpastes and mouthwash as it has a strong sweetening effect but no aftertaste. 
From the late 2000s there has been a push to consume it instead of sugar, and its white granular form means it can be used sprinkled or in place of traditional sugar in cooking and baking in the exact same quantity.

The solubility of D-xylitol (D-xylopentan-1.2.3.4.5-pentaol) in water is approximately 1,690 g/L at room temperature. Xylitol is stable under the common processing conditions of foods.
Xylitol is, depending on the concentration, similarly or slightly sweeter than sucrose and noncariogenic.
In the European Union, xylitol is approved as E 967 for a large number of food applications. In the United States, it is approved for use in foods following Good Manufacturing Practice and it is also approved in many other countries.

Chemical Properties: Xylitol occurs as a white, granular solid comprising crystalline, equidimensional particles having a mean diameter of about 0.4–0.6 mm. 
It is odorless, with a sweet taste that imparts a cooling sensation. 
Xylitol is also commercially available in powdered form, and several granular, directly compressible forms.

Health effects
Dental care
Research has identified carbohydrates, oral bacteria, tooth anatomy, along with their time of interaction as the main pathobiological etiology for dental caries. 
Sucrose is deemed to be the most cariogenic carbohydrate consumed by humans, as it is a substrate to various oral bacteria to produce insoluble polysaccharides and acid.
Streptococcus mutans is a major pathological bacteria. 
It uses carbohydrates via glycolysis to adhere to tooth surfaces with an extracellular matrix, and produces an acidic environment; that acid dissolves the outer tooth enamel layer of the teeth it adheres to.

Xylitol, a sugar alcohol containing 5 carbon-polyol is metabolized via the phospho-enolpyruvate-phospho-transferase pathway (PEP-PTS) in S. mutans, which produces xylitol-5-phosphate as a product.
Xylitol-5-phosphate competes with phosphofructokinase and therefore, results in inhibition of glycolysis via accumulation of glucose-6-phosphate.
Over long periods of time of xylitol use, S. mutans are observed to alter their enzymatic activity.

Burt (2006) conducted a systematic review looking at the effect of sugar alcohols on caries activity.
His systematic review included randomized controlled trials (RCT) as well as observational studies.
Burt concluded that Xylitol displayed non-cariogenic properties in all protocols tested.
Interestingly, he also concluded that mothers chewing xylitol-containing gums effectively inhibited the transmission of S. mutans to their offspring.
Nayak et al. (2014) also conducted a review where they showed the positive effects of Xylitol in gummy bears, syrups, mouthrinse, dentifrice on inhibiting dental caries.
Lastly, Chan et al. (2020) concluded that xylitol has inhibitory effects on S. mutans and Candida albicans.
However, other studies, such as one by Muhlemann et al. (1977) seem to call for more research in this area as the results were inconclusive.
A Cochrane review conducted in 2015 included 10 studies which displayed a low quality evidence on the effectiveness of xylitol containing fluoride toothpastes when compared to fluoride only toothpaste.

Ear aches
In 2011, EFSA "concluded that there was not enough evidence to support" the claim that xylitol-sweetened gum could prevent middle-ear infections with a fast onset, which is also known as acute otitis media (AOM).
A 2016 review indicated that xylitol in chewing gum or a syrup may have a moderate effect in preventing AOM in healthy children.
It may be an alternative to conventional therapies (such as antibiotics) to lower risk of ear aches in healthy children – reducing risk of occurrence by 25% – although there is no definitive proof that it could be used as a therapy for ear aches.

Diabetes
In 2011, EFSA approved a marketing claim that foods or beverages containing xylitol or similar sugar replacers cause lower blood glucose and lower insulin responses compared to sugar-containing foods or drinks.
Xylitol products are used as sucrose substitutes for weight control, as xylitol has 40 percent fewer calories than sucrose (2.4 kcal/g compared to 4.0 kcal/g for sucrose).
The glycemic index (GI) of xylitol is only 7% of the GI for glucose.

Adverse effects
Humans
When ingested at high doses, xylitol and other polyols may cause gastrointestinal discomfort, including flatulence, diarrhea, and irritable bowel syndrome (see Metabolism above); some people experience the adverse effects at lower doses.
Xylitol has a lower laxation threshold than some sugar alcohols but is more easily tolerated than mannitol and sorbitol.

Increased xylitol consumption can increase oxalate, calcium, and phosphate excretion to urine (termed oxaluria, calciuria, and phosphaturia, respectively). 
These are known risk factors for kidney stone disease, but despite that, xylitol has not been linked to kidney disease in humans.

Dogs and other animals
Xylitol poisons dogs.
Ingesting 100 milligrams of xylitol per kilogram of body weight (mg/kg bw) causes dogs to experience a dose-dependent insulin release; depending on the dose it can result in life-threatening hypoglycemia. 
Hypoglycemic symptoms of xylitol toxicity may arise as quickly as 30 to 60 minutes after ingestion. 
Vomiting is a common first symptom, which can be followed by tiredness and ataxia. 
At doses above 500 mg/kg bw, liver failure is likely and may result in coagulopathies like disseminated intravascular coagulation.

Xylitol is safe for cats, rhesus macaques, horses, and rats.
Cats can tolerate ingesting xylitol doses of 1000 mg/kg bw.


Xylitol is equally as sweet as sucrose. 
This property is of advantage to food processors because in reformulating a product from sucrose to xylitol, approximately the same amounts of xylitol can be used. 
Because xylitol has a negative heat of solution, the substance cools the saliva, producing a perceived sensation of coolness, quite desirable in some food products, notably beverages. 
Recently, this property has been used in an iced-teaflavored candy distributed in the European market. 
As of the late 1980s, 28 countries have ruled positively in terms of xylitol for use in commercial products. 
Xylitol has been found particularly attractive for use in chewing gum, mint and hard candies, and as a coating for pharmaceutical products. 
Xylitol has the structural formula shown below, with a molecular weight of 152.1. 
It is a crystalline, white, sweet, odorless powder, soluble in water and slightly soluble in ethanol and methanol. 
It has no optical activity.

Xylitol is a polyhydric alcohol that is a natural sugar substitute com- mercially made from xylan-containing plants (birch) hydrolyzed to xylose. 
Xylitol is as sweet as sucrose, dissolves quickly, and has a negative heat of solution which results in a cooling effect. 
Xylitol has 24 kcal/g. 
Xylitol is used in chewing gum, throat lozenges, and chocolate.


Xylitol is a humectant and skin-conditioning agent. 
Xylitol acts as a humidifier, drawing moisture from the air for skin absorption. 
Some manufacturers also cite a soothing and anti-microbial action. 
Xylitol is a naturally occurring sugar in birch bark and a range of fibrous fruits and vegetables, including corn.


Production Methods of Xylitol:    
Xylitol is synthesized by reduction of D-xylose catalytically, electrolytically, and by sodium amalgam. 
D-Xylose is obtained by hydrolysis of xylan [CAS: 9014-63-5] and other hemicellulosic substances obtained from such sources as wood, corn cobs, almond shells, hazelnuts, or olive waste. 
Isolation of xylose is not necessary; xylitol results from hydrogenation of the solution obtained by acid hydrolysis of cottonseed hulls. 
Xylitol also is obtained by sodium borohydride reduction of D-xylonic acid γ -lactone and from glucose by a series of transformations through diacetone glucose.

Xylitol occurs naturally in many fruits and berries, although extraction from such sources is not considered to be commercially viable. 
Industrially, xylitol is most commonly derived from various types of hemicellulose obtained from such sources as wood, corn cobs, cane pulp, seed hulls, and shells. 
These materials typically contain 20–35% xylan, which is readily converted to xylose (wood sugar) by hydrolysis. 
This xylose is subsequently converted to xylitol via hydrogenation (reduction). 
Following the hydrogenation step, there are a number of separation and purification steps that ultimately yield high-purity xylitol crystals. 
The nature of this process, and the stringent purification procedures employed, result in a finished product with a very low impurity content. 
Potential impurities that may appear in small quantities are mannitol, sorbitol, galactitol, or arabitol.
Less commonly employed methods of xylitol manufacture include the conversion of glucose (dextrose) to xylose followed by hydrogenation to xylitol, and the microbiological conversion of xylose to xylitol.

Xylitol is mostly produced by chemical hydrogenation of xylose which is obtained by hydrolysis of xylans of plants such as birch and beech trees, corn cobs, bagasse, or straw, but also by fermentation of xylose, for example, using Candida species. 
Xylose, especially for hydrogenation, requires a high purity. 
It may be obtained from wood extracts or pulp sulfite liquor, a waste product of cellulose production, by fermentation with a yeast that does not metabolize pentoses. 
Some strains of S. cerevisiae, Saccharomyces fragilis, Saccharomyces carlsbergensis, Saccharomyces pastoanus, and Saccharomyces marxianus are suitable for this purpose.
Hydrolysates of xylan-rich material are often treated with charcoal and ionexchangers to remove by-products causing problems in hydrogenation or fermentation.
Many studies of xylitol production by fermentation have been published. 
Different organisms, substrates, and conditions were investigated. 
As the starting material, xylose or xylose in combination with glucose was used. 
Fermentation was carried out in batch reactors as well as continuously.
Among the variations studied was cell recycling in a submerged membrane bioreactor for C. tropicalis with a high productivity of 12 g/Lh, a conversion rate of 85 % and a concentration of 180 g/L. 
Many studies addressed the immobilization of cells such as S. cerevisiae, C. guilliermondii, or D. hansenii, especially with calcium alginate.

Pharmaceutical Applications of Xylitol:     
Xylitol is used as a noncariogenic sweetening agent in a variety of pharmaceutical dosage forms, including tablets, syrups, and coatings. 
It is also widely used as an alternative to sucrose in foods and as a base for medicated confectionery. 
Xylitol is finding increasing application in chewing gum, mouthrinses, and toothpastes as an agent that decreases dental plaque and tooth decay (dental caries). 
Unlike sucrose, xylitol is not fermented into cariogenic acid end products and it has been shown to reduce dental caries by inhibiting the growth of cariogenic Streptococcus mutans bacteria. 
As xylitol has an equal sweetness intensity to sucrose, combined with a distinct cooling effect upon dissolution of the crystal, it is highly effective in enhancing the flavor of tablets and syrups and masking the unpleasant or bitter flavors associated with some pharmaceutical actives and excipients.
In topical cosmetic and toiletry applications, xylitol is used primarily for its humectant and emollient properties, although it has also been reported to enhance product stability through a combination of potentiation of preservatives and its own bacteriostatic and bactericidal properties.
Granulates of xylitol are used as diluents in tablet formulations, where they can provide chewable tablets with a desirable sweet taste and cooling sensation, without the ‘chalky’ texture experienced with some other tablet diluents. 
Xylitol solutions are employed in tablet-coating applications at concentrations in excess of 65% w/w.
Xylitol coatings are stable and provide a sweet-tasting and durable hard coating.
In liquid preparations, xylitol is used as a sweetening agent and vehicle for sugar-free formulations. 
In syrups, it has a reduced tendency to ‘cap-lock’ by effectively preventing crystallization around the closures of bottles. 
Xylitol also has a lower water activity and a higher osmotic pressure than sucrose, therefore enhancing product stability and freshness. 
In addition, xylitol has also been demonstrated to exert certain specific bacteriostatic and bactericidal effects, particularly against common spoilage organisms.
Therapeutically, xylitol is additionally utilized as an energy source for intravenous infusion therapy following trauma.


Safety: 
Xylitol is used in oral pharmaceutical formulations, confectionery, and food products, and is generally regarded as an essentially nontoxic, nonallergenic, and nonirritant material.
Xylitol has an extremely low relative glycemic response and is metabolized independently of insulin. Following ingestion of xylitol, the blood glucose and serum insulin responses are significantly lower than following ingestion of glucose or sucrose. 
These factors make xylitol a suitable sweetener for use in diabetic or carbohydrate-controlled diets.
Up to 100 g of xylitol in divided oral doses may be tolerated daily, although, as with other polyols, large doses may have a laxative effect. 
The laxative threshold depends on a number of factors, including individual sensitivity, mode of ingestion, daily diet, and previous adaptation to xylitol. 
Single doses of 20–30 g and daily doses of 0.5–1.0 g/kg body-weight are usually well tolerated by most individuals. 
Approximately 25–50% of the ingested xylitol is absorbed, with the remaining 50–75% passing to the lower gut, where it undergoes indirect metabolism via fermentative degradation by the intestinal flora.
An acceptable daily intake for xylitol of ‘not specified’ has been set by the WHO since the levels used in foods do not represent a hazard to health.
LD50 (mouse, IP): 22.1 g/kg
LD50 (mouse, IV): 12 g/kg
LD50 (mouse, oral): 12.5 g/kg
LD50 (rat, oral): 17.3 g/kg
LD50 (rat, IV): 10.8 g/kg
LD50 (rabbit, oral): 16.5 g/kg
LD50 (rabbit, IV): 4 g/kg

Storage    
Xylitol is stable to heat but is marginally hygroscopic. Caramelization can occur only if it is heated for several minutes near its boiling point. 
Crystalline material is stable for at least 3 years if stored at less than 65% relative humidity and 25℃. 
Milled and specialized granulated grades of xylitol have a tendency to cake and should therefore be used within 9 to 12 months. 
Aqueous xylitol solutions have been reported to be stable, even on prolonged heating and storage. 
Since xylitol is not utilized by most microorganisms, products made with xylitol are usually safe from fermentation and microbial spoilage.
Xylitol should be stored in a well-closed container in a cool, dry place.


(2R, 3R, 4S)-pentane-1,2,3,4,5-pentol
(2R,3r,4S)-Pentan-1,2,3,4,5-pentol
(2R,3r,4S)-pentane-1,2,3,4,5-pentol
(2S,3R,4R)-Pentane-1,2,3,4,5-pentaol
(2S,4R)-pentane-1,2,3,4,5-pentol
D-erythro-pentitol
pentane-1,2,3,4,5-pentol
Xylitol
xylitol
Xylitol, Xylit

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