Xylitol Technology

Xylitol Technology

INTRODUCTION Xylitol is a naturally occurring sugar with a wide array of interesting applications.

The most significant fact about Xylitol is the possibility of its

extraction from bagasse, an abundantly available waste material in India. Xylitol can be chemically characterized as a five-carbon sugar alcohol (1, 2, 3, 4, 5 pentahydroxy pentane) with a molecular formula: C5H12O5 (please see box for its physical and chemical properties). Xylitol can be found in small quantities in a various plants, fruits and visitable - the primary sources are raspberries, strawberries, yellow plums, cauliflower, spinach and others. Although widely distributed in nature, its presence in low concentration makes it uneconomic to produce Xylitol on commercial scale from such natural sources.

In this context, the techno-economic feasibility of

extracting the Xylitol from bagasse, as established in Taiwan, is of important commercial significance. Xylitol with the sweetening property matching that of sucrose (sugar) enjoys good applications as sugar substitute for food processing industry. Xylitol produces a perceived sensation of coolness in mouth as it comes in contact with the saliva for its negative heat of solution. This property makes it quite desirable in certain food products, specially beverages. Another significant property of Xylitol has been the prevention of dental cavity as established by the dental caries prevention studies thus making it the best nutritive sugar substitute with respect to caries prevention. C.O.E.&T.,Akola

Xylitol easily 1

Xylitol Technology

metabolizes (independently of insulin) in human body and produces the same amount of energy (4 cal/gm) signifying its application in all diabetic foods. Xylitol has been found particularly attractive as a non sugar sweetener for chewing vitamins and gums, tablets, cough syrups, mouth washes, tooth pastes etc. Hard candies, mints, sugar-less chocolates, gelatin, puddings, jams, baked products, ice-creams etc. are also being marketed using Xylitol as the sweetener. Apart from the above, the adhesive properties of Xylitol have been reported to replace phenolic resin for plywood bonding. As of late 1980s, 28 countries have been using Xylitol in commercial products. In early 90s, an annual production of Xylitol has been reported as around 5000 tones in the world. Around 95% of the world's production belongs to two firms from Finland and the balance quantity is distributed among four firms in Japan, one in China and two in Switzerland. In addition to a number of companies in USA that are interested in large-scale production of Xylitol in the future, similar interests are also being pursued in Switzerland, Finland and Germany among others. Currently, the major use of Xylitol has been in the manufacture of chewing gums.

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Xylitol Technology

Physical and chemical properties of Xylitol Molecular weight

: 152.15

appearance

: white, crystalline powder

odour

: none

boiling point

: 126° C (at 760 mm)

melting point

: 92° to 96° C

solubility at 20°

: 169 gms in 100 gms of water, sparingly

soluble in ethanol and methanol pH in water (1 gm/10 ml)

: 5 to 7

heat of solution

: - 34.8 cal/g (endothermic)

calorific value

: 4.06 cal/gm

Process of manufacture C.O.E.&T.,Akola

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Xylitol Technology

1. Xylitol from Pentosans The synthesis of Xylitol from natural products is based on the chemistry of pentosans occurring in many plants. Xylan, a constituent of pentosan, is a polysaccharide; this can be hydrolized into D- xylose. The synthesis reactions can be summarized as under: Hydrolysis (C5 H8 O4)n

Hydrogenation n(C5 H10 O5)

n(C5

H12

O5) Pentosans

Xylose

Xylitol

like xylan Sud-Chemie AG, Munich, Germany in their patents granted in 1976 (U.S. Patent # 3980719) had described a process for preparing Xylitol by acid hydrolysis of xylan to produce a solution containing xylose and acetic acid. The solution was filtered for recovering unhydrolyzed acid. The solution was further subjected to an adsorbent to remove proteins, tannins and pectins. The purified solution was evaporated under vacuum to a viscous virtually water free syrup, thereby removing all the acid acid from the said solution. The result and syrupy solution was further diluted with water and pH maintained in the range of 6.5 to 7.5. The diluted solution containing xylose was then hydrogenated using Raney nickel catalyst, followed by the recovery of Xylitol from the solution. Another U.S. patent (# 4008285), applied from Finland and granted in 1977, describes a maker of producing Xylitol on commercial scale by acid hydrolysis of raw material containing pentosan. The process differs from the earlier one in the C.O.E.&T.,Akola

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Xylitol Technology

step after hydrolysis where the inorganic salts, organic impurities and colour are removed by treating the solution with an ion exchange resin and activated carbon. The solution is further fractionated by ion exchange chromatographic techniques to yield a high purity xylose solution. The solution is then hydrogenated in presence of a catalyst and subjected to ion exchange chromatographic fractionation again to recover Xylitol of high purity.

2. Xylitol from Bagasse Rice and cotton seed hulls, bagasse, corn stalks, coconut shells etc. with rich Xylan contents can also be used for production of Xylitol. Technology from Taiwan The Taiwan Sugar Research Institute has dated out extensive research work on the possibilities of commercial exploitation of Xylitol from bagasse.

A process for continuous production of Xylitol from bagasse on

commercial scale has been developed by the Institute. The manufacturing process involves shredding of bagasse into smaller particles (size: max. 1.5 cm long) and removal of pith, it is thoroughly washed with water to remove the dissolved mineral matters.

Drying of bagasse reduces its

moisture content to 10 percent and the ash content is maintained at maximum 1 percent. Hydrochloric acid liquor found superior to sulphuric acid, which was used earlier, and bagasse are fed into a mixer in a ratio of HCl : dry bagasse as 0.25

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Xylitol Technology

to 12 percent. These are mixed thoroughly by agitation in a stirred tank reactor and passed on to a rotary kiln (autoclave) fitted with a school feeder. The acid liquor and bagasse are steam heated to 100-125 deg. C with a residence of 40-75 minutes in the rotary kiln. This treatment helps in pre-hydrolysis of hemicellulose content of a bagasse. The output from the rotary kiln (the mixture of bagasse with acid liquor) is post-hydrolized continuously on a screen conveyor where the mixture is sprinkled with hot water (100 degree C) and leached the liquor. The leached liquor is collected at conical bottomed vessels placed under the screen conveyor and it is recycled.

The post-hydrolysis step completely extracts the xylose content of

bagasse. The hydrolysate, collected at conical bottomed vessels, containing 17-20 percent of xylose, maybe further fermented for alcohol production of taken up for xylose separation. Water is removed from the spent bagasse in a screw press and the residue is used for pulp making. The following table presents various process parameters for the extraction of xylose by acid hydrolysis of bagasse.

MANUFACTURING

OF

XYLITOL

FROM

BAGASSE

(TAIWAN

TECHNOLGY)

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Xylitol Technology

Xylose From Bagasse - A Schematic Diagram Technology from China A Chinese technology offer for producing Xylitol made available through the Asian and Pacific Center for transfer of technology (APCTT), New Delhi is also based on utilization of agricultural wastes such as bagasse or corn cob. The process has little impact on environment and does not produce any waste gas.

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Xylitol Technology

The waste dredge produce during the process can be used as fuel or culture for mushroom cultivation. After neutralization, waste water can be drained away or an aerobically treated if it contains organic substances.

The process has been

commercialized in China.

Process description Bagasse (corn cob) → hydrolysis and dredge removal → decolorization → ion exchange → concentration → crystallization → separation from mother liquor → finished product. Inputs required Steam - 9.5 tons/hr (P = 0.6 Mpa), building - 7800 sq.m., land – 4000 sq. m., water - 110 tons/hr, power - figure not known. Manpower required Total - 110, technicians - 12, skilled - 76, unskilled – 28 production capacity - 500 tons/year Raw materials bagasse (corn cob) -17,800 tons/year (6000 tons/year), sodium carbonate 800 tons/year, sulphuric acid (not less than 92% conc. ) -1200 tons/year, activated carbon - 90 tons/year.

Economic data Machinery and equipment (FOB)

: U.S. $4.1 million

Know-how fee

: U.S. $650,000

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Xylitol Technology

Training fee

: U.S. $80,000

Operational cost/year

: U.S. $ 1.8 million

Technology transfer details Turnkey transfer, the technology supplier could also consider supply of process plant and equipment, buyback arrangement. Another Chinese process technology, offered through APCTT, for making Xylitol involves safe and flexible process line with simple oppression and low investment. The effluents can be simply treated within the battery limit. All waste discharges from the plant are in accordance with international standards. The solid waste residues can be used as fuel for brick manufacturing. The process has already been commercialized in China.

Process description Bagasse → hydrolysis → purification → hydrogenation → concentration → crystallization → drying and packing. Inputs required Land – 4000 sq. m., building – 5000 sq. m., water – 2500 tons/ton of product, power – 5500 KWH/ton of product. Manpower required Total - 200, technicians - 20 Production capacity 600 - 700 tons/year (300 working days). Raw materials

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Xylitol Technology

Bagasse, Sulphuric Acid, Caustic soda. Economic data Total Project Cost -U.S. $ 5.5 million, Machinery and Equipment (FOB)-U.S. 3.0 million, Know-How fee-U.S.$ 400,000, Training fee-U.S. $ 50,000, Operating cost - as per local labor and material costs. Technology transfer details Transfer of know-how, offer of consultancy, technical assistance, supply of process plant and equipment, training of personnel.

3. Other processes A search of the IBM site on the Internet on patents applied for and granted by the U.S. patent and trademark office(USPTO) reveals the following processes: Xylitol from Hemicellulosic materials A patent (# 3627636) granted to Hoffman-La Roche, New Jersey in December, 1971 describes a process for producing Xylitol from lignin-free Hemicellulosic materials. In this process, the polysaccharides of Hemicellulose have been converted to monosaccharides which on fermentation with a hexose fermentation yeast and further hydrogenation of the aqueous medium produces Xylitol. Xylitol by Fermentation A Finnish patent (# 50 81,026) granted by USPTO in January, 1992 deals with the method of preparing Xylitol by fermenting an aqueous solution

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Xylitol Technology

containing xylose and other free hexoses with a yeast stram.

While the yeast

converts xylose to Xylitol, it converts hexoses to ethanol. The Xylitol-rich fraction is then separated from the fermented solution by chromatographic method.

Manufacturing Xylitol by using recombinant microbial hosts A resent Finnish patent (# 5631150 ) granted in May, 1997 by USPTO reports production of Xylitol from a recombinant microbial host.

The process

involves growing an arabitol producing yeast or fungus under the conditions suitable for synthesizing Xylitol. The arabitol producing yeast or fungus is modified to Xylitol in a single fermentation step. The recombinant microbial post is transformed with a DNA encoding a D- xylulose forming D- arabitol dehydrogenase and with a DNA encoding Xylitol dehydrogenase. Xylitol is then recovered from the above solution.

Xylitol: potential applications Xylitol has been used in a wide range of products. It can be used as an additive in food industry, in pharmaceutical industry, health food, beverage industry, cakes, gums as sweetener and in light industry as raw material. A search of international the literature and also the patents on various applications of the Xylitol is summarized in the following sections.

Xylitol in food products C.O.E.&T.,Akola

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Xylitol Technology

A chewing gum with improved storage qualities was patented (# 4 000320) by general foods corporation, New York, U.S.A. in December, 1976. The patent relates to a chewing gum comprising gum base, sweetener, flavor and Xylitol. The Xylitol content, less than 50 percent of the total gum composition is effective in improving the storage quality and stability. The U.S. patent (#34105801) awarded to an Italian company in 1978 describes a coated edible product and its preparation. The product consists of a core portion and a shell enveloping the core. The shell comprises of a mixture of Xylitol microcrystals with solid fat (selected from the group consisting of mono-,die-and triglycerides of palmitic-, stearic- and oleic acids and cocoa butter) in a proportion of 0.50 to 15 parts by weight of fatty substance to 100 parts by weight of Xylitol. A Japanese patent, granted in 1990, describes the application of Xylitol in a granular quality improver for frozen fish and meat products. The granular quality improver is manufactured by mixing sugar, sugar alcohol (Xylitol), phosphate salts and optional fats - this is pressure moulded and pulverized. The granules prevent denaturation by freezing, give firm texture and maintain whiteness; these are more convenient than the conventional additives. A patent for a low calorie artificial honey using Xylitol was applied for in 1992 in U.S.A. The honey based food product having taste and texture resembling to that of pure honey while having a low-calorie content has been reported. The formulation contains low-calorie polysaccharides such as polydextrose and a polyol (sorbitol, maltitol, Xylitol etc.).

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Xylitol Technology

In a Chinese patent application of 1993, the use of Xylitol in the preparation of medicinal chewing gum for oral hygiene and treatment of oral disease has been reported. The chewing gum is prepared by mixing bactericides, powdered sugar, gum base and a pre-heated starch syrup. It may also contain other ingredients such as softeners and fragrance. The bactericides are chosen from chlorhexidine citrate, chlorhexidine fluoride and ribavirin. The hard coated chewing gum with improved shelf life with Xylitol and polyol coatings was patented (# 5376389) by Wrigley Jr. Co., Chicago, U.S.A. in 1994. The patent relates to a duel composition hard coated chewing gum which comprises 35-90 percent by weight of gum center (a chewing gum base + flavoring agents) and 10-65 percent by weight of an outer coating (containing 50-100 percent by weight of Xylitol and non-Xylitol polyol). The duel composition hard coated type is suitable for chewing gum pellets which have improved shelf life with respect to atmospheric moisture. A Japanese patent, awarded in 1995, describes the method for manufacturing chocolate containing sugar substitute. The mouth-feel of the plates having sugar alcohol impacted Xylitol) as sugar substitute has been improved by using diglycerides. 'Xylifresh' is a new chewing gum launched by Leaf Inc., Chicago, U.S.A. The gum is being promoted as the first to curb bacteria and reverse early decay. Xylitol, the active ingredient of xylifresh, has been long accepted as cavity fighter in parts of the -Europe.

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Xylitol Technology

Xylitol for Dental and Medical Applications Colgate Palmolive company, New York, U.S.A. patented (# 3970747) a humectant sweetener in 1976. This is a dentifrice containing non-calorigenic humectant sweetener.

A dentifrice is nothing but an aqueous dental cream

(toothpaste) containing at least 10 percent water and a humectant. The humectant comprises about 10 percent by weight of a Xylitol solution in water in combination with other polyols. The use of Xylitol in pharmaceutical preparation allowing it to penetrate the blood-brain barrier has been reported in a Japanese patent of 1993. Of pure sugar combination selected from a group of comprising meso-erythritol, Xylitol, galactose, lactose, fructose, glucose and others had been used. In an European patent application of 1994, the use of Xylitol has been cited for medicament for topical application to the eye for treatment of increased intraocular pressure. It has been reported that the intraocular pressure was lowered by application of ophthalmic solution containing a polyol (0.5 -10 percent by weight) such as sorbitol, mannitol or Xylitol. In clinical trials, the application of one drop of five percent sorbitol solution twice daily to a group of patients decreased the mean intraocular pressure from 27 to 19 mm Hg within seven days. A Finnish paper, published in 1994, reported the retention of calcium from various Xylitol-calcium combinations in rats. Xylitol increases the intestinal absorption of calcium been tested in rats. In the study, and optimum Xylitol: calcium molar ratio for calcium absorption and retention was determined in 10 weeks. The

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Xylitol Technology

highest retention rate of radioactive calcium (45Ca) was found when 114 mg of Xylitol was given with calcium (Xylitol : Ca molar ratio of 1:5). For companies and, the selection of 45Ca was determined from 4-lactose : CaCl2 combinations and from calcium lactate and calcium citrate salts. The results favor the use of a Xylitol: Ca molar ratio of 1:5 in Ca supplements. In June, 1995 Colgate Palmolive company of U.S.A. patented (# 5424059) the application of Xylitol as an antibacterial and antiplaque dentifrice. It is reported that the Xylitol used in the dentifrice inhibits plaque information, reduces gingivitis and caries. The dentifrice essentially consists of an orally acceptable aqueous humectant Xylitol vehicle, about 20-75 percent by weight of a dentally acceptable and water insoluble Ca or Mg alkaline earth metal (as polishing agent) and a non toxic to fluoride compound to release 25-5000 ppm of fluoride ion. The dentifrice also contains an effective antiplaque (selected from halogenated diphenyl ethers,

halogenated

salicylanilides,

benzoic

esters,

sesquiterpene

alcohols,

halogenated carbanilides and phenolic compounds) and about 0.1 percent by weight of Xylitol. Another antimicrobial oral composition containing Xylitol has been patented (# 553 1982) by, Colgate Palmolive, U.S.A. in July, 1996. It is reported that the older composition is effective in reducing dental caries and fissures even without a fluoride ion source. This contains about 10-30 percent by weight of a water insoluble and dentally acceptable siliceous polishing agent, an antiplaque and

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Xylitol Technology

noncationic antimicrobial agent, an antibacterial agent (0.05-4 percent by weight) and at least about 0.1 percent by weight of Xylitol. An antimicrobial mouthwash of pleasant taste was patented (# 5560906) by Oral Technology Laboratories, U.S.A. in October, 1996.

The

mouthwash has been reported to be effective in removing dental plaque. It does not content any alcohol, sugar or artificial sweetener making it safe for use by diabetics, alcoholics and others. The formation consists of water, glycerin, sodium benzoate, cetylpyridinium chloride, citric acid, maltol, Xylitol, a flavoring agent (for pleasant but biting taste) and a coloring agent. A fluoride toothpaste with Xylitol has been launched by Digitemp Industries Sdn. Bhd., Malaysia. The manufacturer in their advertisement reports that Xylitol fights tooth decay and control is bad breath by resisting fermentation by mouth bacteria, neutralizing acid produced by fermenting carbohydrates, inhibiting plaque accumulation and calorigenic bacteria and by promoting demineralization. The dental benefits of Xylitol have been demonstrated as such in numerous field studies and this has led to official endorsements by the dental associations in Finland, Norway and Sweden.

Other Applications A paint composition containing Xylitol was patented (# 3925278) by new Japan chemical company Ltd., Japan in 1975.

The coating composition

essentially contains a film forming binder selected from the group consisting of tar epoxy, alkyd and modified alkyd resin. The binder properties have been improved

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Xylitol Technology

by adding a thickening agent

(0.001-10 percent by weight) consisting of a

condensation product of 1 to 3 moles of a polyhydric alcohol (Xylitol, sorbitol, heptitol) and one mole of aromatic monoaldehyde (benzaldehyde, methyl benzaldehyde, nitrobenzaldehyde, aminobenzaldehyde, napthylaldehyde and several others). Xylitol as a reusable heat device has also been reported. In a patent (# 4295517) awarded by USPTO to a group of Swiss scientists in 1981 describes a method of providing the heat source by adding Xylitol as a heat storage material. The process involved heating Xylitol in a container to a temperature above its melting point, then cooling the resulting melt to a temperature below the melting point of Xylitol without crystallizing it and further initiating the crystallization of Xylitol thus releasing the heat of crystallization of Xylitol as the source of heat. In a French patent application of 1993, the use of a number of simple polyols such as Xylitol and their combinations in cosmetic preparations has been claimed. The selected polyols help restore the balance of skin flora while inhibiting pathogenic germs.

Conclusion India with over 400 sugar mills produces around 70 million tons of bagasse every year. The TIFAC reports on 'Use of Biomass (Bagasse) for Paper and Pulp Industry' and ' System Approach to Bagasse Utilization' in detail the national and international trends and scenarios on various means of bagasse utilization. As one of the reports, the global trends in bagasse utilization is mostly concentrated in two areas: C.O.E.&T.,Akola

a) generation of power has practiced in Mauritius, 17

Xylitol Technology

Hawaii, U.S.A. etc. and b) paper manufacture, India has carried out extensive research on bagasse utilization for paper and pulp of making and successfully solved many problems by implementing design improvements and proper mix of chemical and mechanical processes along with using 10-50 percent bagasse with hardwood pulp or waste paper pulp. The TIFAC studies for the recommend that a detailed technoeconomic evaluation should be carried out for improved utilization of bagasse by various means. It is suggested that at least 10 percent of bagasse available maybe diverted to pulp and paper manufacture and further 10 percent may be consumed for manufacturing various types of particle boards. The TIFAC studies also cover Xylitol as an important product from bagasse. Xylitol has been identified as a critical raw material for producing feed yeast, food industry, pharmaceutical and chemical industries. It is evident from this article based on patent searches and other technology trends that Xylitol enjoys the excellent potential for commercial applications. Xylitol has been categorized as a degree (on safety scale) for its use as a food additive. The process details for extracting Xylitol from bagasse as described in the Taiwanese experiment covered in this article do not appear complicated and it definitely merits experimentation on a pilot-scale so as to establish the optimal process parameters. Such a project maybe taken up in right earnest by the industries with venture capital financing or funding support under various technology development schemes of the Government of India. It is inferred by TIFAC study that

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Xylitol Technology

sugar mills already manufacturing or any chemicals should seriously consider seeking up the plant for the Xylitol extraction. At least 2-5 plants for Xylitol should be set up in the near future with a national plan of setting up 20 plants in the next five years. The demand for Xylitol may be much in the country today due to lack of awareness and availability.

The techno- economic feasibility for extracting

Xylitol from bagasse (and using the residues for paper making or boiler fuel) may lead to a cheaper cost of the product compared to one obtained from birch wood or hard wood chips as practiced in the European countries.

This may help in

developing an export market for Xylitol produced in India.

References 1. www.Xylitol.org 2. www.xclear.com 3. www.Xylitoltechnology.com 4. A journal 'Chemical Engineering World' -

Jan. 98 , Vol. XXXVIII, Page No. 103-108

5. Organic Chemistry By Bahl.

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