Xylitol

XYLITOL : Technology & Business Opportunities Soumitra Biswas, Nirmala Vashishtha 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 & chemical properties). Xylitol can be found in small quantities in various plants, fruits and vegetables - 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 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 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. Xylitol easily 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 &

gums, tablets, cough syrups, mouth washes, tooth pastes etc. Hard candies, mints, sugar-less chocolates, gelatin, puddings, jams, baked products, ice-creams etc. a re 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 using xylitol in commercial products. In early 90s, an annual production of xylitol has been reported as around 5000 tons 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 p ursued in Switzerland, Finland and Germany among others. Currently, the major use of xylitol has been in the manufacture of chewing gums. Physical & Chemical Properties of Xylitol

Molecular Weight : 152.15  Appearance : White, crystalline powder  powder  Odour : None Boiling Point : 126 ฐ C (at 760 mm) Melting Point : 92 ฐ to 96 ฐ C Solubility at 20 ฐ : 169 gms in 100 gms of water, sparingly soluble in ethanol & methanol pH in water (1gm/10 ml) : 5 to 7

Heat of Solution : - 34.8 cal/g (endothermic) Calorific Value : 4.06 cal/gm 2.0 Process of Manufacture

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 hydrolyzed into Dxylose, which is also known as wood sugar having sweet taste. Xylitol can be synthesized by hydrogenation of xylose. The synthesis reactions can be summarized as under : Hydrolysis Hydrogenation (C5H8O4)n ---------> n(C 5H10O5) ------------> n(C 5H12O5) pentosans xylose xylitol like xylan Sud-Chemie AG, Munich, Germany in their patents granted in 1976 (US 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 organic residues and removing the hydrolyzing 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 acetic acid form the said solution. The resultant 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 recovery of xylitol from the solution.  Another US patent ( # 4008285), applied from Finland and granted in 1977, describes a method of  producing xylitol on commercial scale by acid hydrolysis of raw material containing pentosan. The process differs from the earlier one in the step after hydrolysis where the inorganic salts, organic impurities & 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. 2.1 Xylitol from Bagasse

Rice & cotton seed hulls, bagasse, corn stalks, coconut shells etc. with rich xylan contents can also be used for production of xylitol. 2.1.1 Technology from Taiwan

The Taiwan Sugar Research Institute has carried 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 small particles so as to improve the yield of xylitol . After shredding of bagasse into small particles (size : max. 1.5 cms 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 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 screw feeder. The acid liquor & bagasse are steam heated to 100-125 deg. C with a residence time of 40-

75 minutes in the rotary kiln. This treatment helps in pre-hydrolysis of hemicellulose content of  bagasse. The output from the rotary kiln (the mixture of bagasse with acid liquor) is post-hydrolysed continuously on a screen conveyor where the mixture is sprinkled with hot water (100 deg. C) and leached 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 per cent of  xylose, may be further fermented for alcohol production or 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 : Table 2.1.1 : Process Parameters & Yield for Xylose Extraction

-

Test No.

-

Prehydrolysis

-

Hydrolysate

-

-

Pure Temperature Time Xylose Residual Xylose Xylose: HCl: Deg. C (mins.) content (%) acid  Yield HCl Bagasse content (%) (MT/MT) (%) (%)

1. 2. 3. 4. 5. 6. 7. 8.

1.0 1.5 2.0 2.0 4.0 1.0 1.0 2.0

100 100 100 100 100 125 125 125

75 75 75 75 75 60 90 40

15.2 17.6 20.5 15.9 16.3 20.0 16.5 9.2

2.3 2.9 3.5 3.2 5.6 2.5 1.8 1.5

48.8 65.3 74.8 70.0 75.0 74.0 75.0 81.0

14.3 12.7 11.5 10.7 6.1 23.0 24.5 13.2

The test # 2 produces 17.6 percent of xylose from prehydrolysis of bagasse using HCl @ 1.5 percent of dry bagasse at 100 deg. C for 75 minutes. The yield of xylose as reported is only 65.3 percent whereas the acid consumption in found to the lower (one ton of HCl produces 12.7 ton of  xylose). In case of test # 6 carried out at 125 deg. C, xylose yield to acid used has been very high (23 tons of xylose per ton of HCl used). As per the Taiwanese researchers, the process parameters for experiment # 2 are more suitable not for xylose yield but for remaining hemicellulose in the residual bagasse. This results in superior quality pulp production from the residue. 2.1.2 Technology from China

 A Chinese technology offer for producing xylitol made available through the Asian & Pacific  Centre 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. The waste dredge produced during the p rocess can be used as fuel or  culture for mushroom cultivation. After neutralization, waste water can be d rained away or  anaerobically treated if it contains organic substances. The process has been commercialized in China. Process Description

Bagasse (corncob) -> Hydrolysis & 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 - 7,800 sq. m, Land - 4,000 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 (Corncob) - 17,800 tons/year (6,000 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 & equipment (FOB) : US $4.1 million Know-how Fee : US $650,000 Training Fee : US $80,000 Operational Cost/Year : US $1.8 million Technology Transfer Details

Turnkey transfer, supply of process plant & equipment, buy-back arrangement could also be considered by the technology supplier.  Another Chinese process technology, offered through APCTT, for making xylitol involves safe & flexible process line with simple operation 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 b rick manufacturing. The process has already been commercialized in China. Process Description

Bagasse -> Hydrolysis ->Purification -> Hydrogenation -> Concentration -> Crystallization ->Drying & Packing Inputs Required 

Land - 4,000 sq. m, Building - 5,000 sq. m, Water - 2,500 ton/ton of product, Power - 5,500 KWH/ton of product Manpower Required 

Total - 200, Technicians - 20 Production Capacity 

600 -700 tons/year (300 working days) Raw Materials

Bagasse, Sulphuric Acid, Caustic Soda Economic Data

Total Project Cost - US $5.5 million, Machinery & Equipment (FOB) - US $3.0 million, Know-how Fee - US $400,000, Training Fee - US $ 50,000, Operating Cost - as per local labour and material costs.

Technology Transfer Details

Transfer of know-how, Offer of consultancy, Technical assistance, Supply of process plant & equipment, Training of personnel. 2.2 Other Processes

 A search of the IBM site on Internet on patents applied for and granted by the US Patent & Trademark Office (USPTO) reveals the following processes : 2.2.1 Xylitol from Hemicellulosic Materials

 A patent (# 3627636) granted to Hoffmann-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 . 2.2.2 Xylitol by Fermentation

 A Finnish patent (# 5081026) granted by USPTO in January, 1992 deals with the method of  preparing xylitol by fermenting an aqueous solution containing xylose & other free hexoses with a yeast strain. While the yeast converts xylose to xylitol , it converts hexoses to ethanol. The xylitolrich fraction is then separated from the fermented solution by chromatographic method. 2.2.3 Manufacturing Xylitol by using Recombinant Microbial Hosts

 A recent 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 host 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. 3.0 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 literature and also the patents on various applications of xylitol is summarized in the following sections. 3.1 Xylitol in Food Products

 A chewing gum with improved storage qualities was patented (# 4000320) by General Foods Corporation, New York, USA in December, 1976. The patent relates to a chewing gum comprising gum base, sweetener, flavour and xylitol. The xylitol content, less than 50 percent of the total gum composition, is effective in improving the storage quality and stability. The US patent (# 4105801) 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 en veloping the core. The shell comprises of a mixture of xylitol microcrystals with solid fat (selected from the group consisting of mono-, di-& triglycerides of palmitic-, stearic- & 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 & 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 USA. The honey based food product having taste & texture resembling to that of pure honey while having a lowcalorie content has been reported. The formulation contains low-calorie polysaccharides such as polydextrose & a polyol (sorbitol, maltitol, xylitol etc.). 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 & 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. Company, Chicago, USA in 1994. The patent relates to a dual composition hard coated chewing gum which comprises 35-90 percent by weight of gum centre (a chewing gum base + flavouring agents) and 10-65 percent by weight of an outer coating (containing 50-100 percent by weight of xylitol and non-xylitol polyol). The dual 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 chocolates having sugar alcohol (xylitol) as sugar  substitute has been improved by using diglycerides. 'Xylifresh' is a new chewing gum launched by Leaf Inc., Chicago, USA. The gum is being promoted as the first to curb bacteria & reverse early decay. Xylitol , the active ingredient of Xylifresh, has

been long accepted as cavity fighter in parts of Europe. 3.2 Xylitol for Dental & Medical Applications

Colgate Palmolive Company, New York, USA patented (# 3970747) a humectant sweetener in 1976. This is a dentifrice containing non-cariogenic 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. A pure sugar combination selected from a group comprising meso-erythritol, xylitol , galactose, lactose, fructose, glucose and others has 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 5 percent sorbitol solution twice daily to a group of patients decreased the mean intraocular pressure from 27 to 19 mm Hg within 7 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 when tested in

rats. In this study, an optimum xylitol : calcium molar ratio for calcium absorption & retention was determined in ten weeks. The 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 comparison, the selection of 45Ca was determined from 4-lactose : CaCl2 combinations and from calcium lactate & calcium citrate salts. The results favour the use of a xylitol : Ca molar ratio of 1:5 in Ca supplements. In June, 1995 Colgate Palmolive Company of USA patented (# 5424059) the application of xylitol as an antibacterial & antiplaque dentifrice . It is reported that xylitol used in the dentifrice inhibits plaque formation, reduces gingivitis & caries. The dentifrice essentially consists of an orally acceptable aqueous humectant xylitol vehicle, about 20 - 75 percent by weight of a dentally acceptable & water insoluble Ca or Mg alkaline earth metal (as polishing agent) and a non-toxic 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 to 40 percent by weight of xylitol .  Another antimicrobial oral composition containing xylitol has been patented ( # 553 1982) by Colgate Palmolive, USA in July, 1996. It is reported that the oral composition is effective in reducing dental caries & fissures even without a fluoride ion source. This contains about 10 - 30 p ercent by weight of a water insoluble & dentally acceptable siliceous polishing agent, an antiplaque & 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, USA in October, 1996. The mouthwash has been reported to be effective in removing dental plaque. It does not contain any alcohol, sugar or a rtificial sweetener making it safe for use by diabetics, alcoholics and others. The formation consists of water, glycerin, sodium benzoate, cetylpyridinium chloride, citric acid, maltol, xyltiol, a flavouring agent (for pleasant but b iting taste) and a colouring 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 & controls bad breath by resisting fermentation by mouth bacteria, neutralizing acid produced by fermenting carbohydrates, inhibiting plaque accumulation & cariogenic bacteria and b y 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 & Sweden. 3.3 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 & modified alkyd resin. The binder properties have been improved 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, naphthylaldehyde & 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. 4.0 Conclusion

India with over 400 sugar mills produces around 70 million tons of bagasse e very year. The TIFAC reports on 'Use of Biomass (Bagasse) for Paper & Pulp Industry ' and 'System Approach to Bagasse Utilization' cover in detail the national & international trends & scenarios on various means of bagasse utilization. As per the reports, the global trends in bagasse utilization is mostly concentrated in two areas : a) generation of power as practised in Mauritius, Hawaii, USA etc. and b) paper manufacture. India has carried out extensive research on bagasse utilization for paper & pulp making and successfully solved many problems by implementing design improvements and proper mix of chemical & mechanical processes along with using 10-50 percent bagasse with hardwood pulp or waste paper pulp. The TIFAC studies further recommend that a detailed techno-economic evaluation should be carried out for improved utilization of bagasse by various means. It is suggested that at least 10 percent of bagasse available may be diverted to pulp & 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 & other technology trends that xylitol enjoys excellent potential for commercial applications. Xylitol has been categorised 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 pilotscale so as to establish the optimal process parameters. Such a project may be 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 sugar mills already manufacturing organic chemicals should seriously consider setting up the plant for 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 not be much in the country today due to lack of awareness & 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 practised in the European countries. This may help in developing an export market for xylitol produced in India. References

Rao, Manohar. P. J. (1997) - Industrial utilization of sugarcane & its co-products Buckl, H., Fahn, R., Hofstadt, C. E., Sud-Chemie AG, Germany : US Pat. No. 3980719 (Sept. 14, 1996) Melaja, Asko. J. Hamalainen, L., Finland : US Pat. No. 4008285 (Feb. 15, 1977) Jaffe, Gerald M., Weinert Peter H., et al., Hoffmann - La Roche Inc., New Jersey : US Pat. No. 3627636 (Dec. 14, 1971) Heikkila, H., Rahkila, L., et al., Suomen Xyrofin Oy, Finland : US Pat No. 5081026 (Jan. 14, 1992) Harkki, Anu M., Myashikov, A. N., et al. , Xyrofin Oy, Finland : US Pat No. 5631150 (May 20, 1997)

Klose, Robert E., Sjonvall, Ragnar E., et al., General Foods Corporation, New Jersey : US Pat. No. 4000320 (Dec. 28, 1976) Dogliotti, A., P. Ferrero & C. S.p.A., Italy : US Pat. No. 4105801 (Aug 08, 1978) Koga, H., Miyabe H., et al., Japan Organo Company Ltd., Japan : Pat. No. 2150256 (June 08, 1990)  Ayraham, Dvir, N., Nitzan, I., et al., USA : US Pat. No. 5447743 (June 17, 1992) Song, G., et al., Jinzhou Pharmaceutical No. 1 Factory, China : Pat. No. 1069410 (March 03, 1993) Reed, Michael A., Hook, J. S., et al., Wrigley Jr. Company, Chicago, USA : US Pat. No.5376389 (Dec. 27, 1994) Ohata, T., Yamamuro, H., Morinaga & Company, Japan : Pat No. 0779703 (March 28, 1995) Barth, Jordan B., Colgate Palmolive Company, New York : US Pat. No. 3970747 (July 20, 1976) Naito, Albert, T., Japan, Pat. No. 05339148 (Dec. 2 1, 1993) Franz, H., Kompa, H. E., et al., European Pat. No. 585896 (March 09, 1994) Haemaelaeinen, M. M., Retention of Ca from various Xylitol -Ca combinations in Rats, Proceedings of Society of Experimental Biology & Medicine, 1994, 205 (3) Finland Prencipe, M., Rustogi, K. N., Gaffar, A., et al., Colgate Palmolive Company, New York : USPat. No. 5424059 (June 13, 1995) Gaffar, A., Nabi, N., Afflitto, J., Colgate Palmolive Company, New York : US Pat. No. 5531982 (July 02, 1996) Scodari, N. F., Chattman, R. L., Oral Technology Laboratories Inc., USA : US Pat. No. 5560906 (Oct. 01, 1996) Murai, K., Choshi, Y., Kobayashi, T., New Japan Company Ltd., Japan : US Pat. No. 3925278 (Dec. 09, 1975) Guex, W., Klaeui, H., Pauling, H., Voirol, F., Switzerland : US Pat. No. 4295517 (Oct. 20, 1981) Considine, D. M., Scientific Encyclopedia, 8 th Edition, Van Nostrand's 'Use of Biomass like Bagasse for Pulp & Paper Industry', a techno-market survey report (TMS : 086), TIFAC 'System Approach to Bagasse Utilization', a techno-market survey report (TMS : 103), TIFAC For further information, please contact Mr. S. Biswas at [email protected] Top