FORM 2
THE PATENTS ACT 1970
(39 of 1970)
&
The Patent Rules 2003
COMPLETE SPECIFICATION
(see sections 10 & rule 13)
1. TITLE OF THE INVENTION
A PROCESS FOR RECOVERY OF XYLITOL WITH HIGH YIELD AND PURITY
2. APPLICANT (S)
NAME NATIONALITY ADDRESS
LALI; ARVIND Indian DBT-ICT Centre For Energy Biosciences, Institute
MALLINATH of Chemical Technology, Nathalal Parikh Marg,
Matunga (East), Mumbai, 400 019
The following specification describes the nature of the invention and the manner in which it is to be performed.

FIELD OF INVENTION
This invention relates to a process for recovery of xylitol with high yield and purity. A specific aspect of this invention relates to a method for the isolation of xylitol from crude feedstock by using the hybrid process comprising appropriate coupling of one or more membrane filtration, negative hydrophobic interaction/reverse phase chromatographic adsorption and crystallization from water immiscible or partially immiscible organic solvent.
BACKGROUND OF THE INVENTION
The pentahydric alcohol, xylitol is the sugar alcohol derived from the reduction of xylose (C5H10O5). Xylitol is a naturally occurring, five-carbon sugar alcohol which has the same sweetness and has two third of caloric content as that of sucrose, xylitol is found in small . amounts in many fruits and vegetables and is produced in the human body during normal metabolism. Xylitol has certain known metabolic, dental and technical characteristics which makes it an attractive sugar substitute in various contexts.
Xylitol is metabolized independently of insulin, so it can be safely consumed by insulin dependent and non-insulin dependent diabetics. Additionally, xylitol has been shown to delay-gastric emptying and to possibly suppress food intake which means it may have an important role in weight reducing diets.
Xylitol is also a non-cariogenic, and possibly even a cariostatic substance. In the mouth, sucrose and other carbohydrates are fermented by Streptococcus mittans and other bacteria, generating acid which lowers the pH, demineralises tooth enamel and leads to dental caries and other acid by-products of fermentation contribute to tooth decay. Studies have also produced data which suggests that xylitol even actively suppress the formation of new caries and even "reverse" existing lesions by inducing re mineralisation.
From a taste perspective, xylitol does not typically manifest an unpleasant aftertaste like other sugar substitutes and, because of the high energy required to dissolve one gram of xylitol, it produces a pleasant "cooling" effect in the mouth.
Despite xylitol's advantages, the utilization of xylitol on a commercial scale has been limited by its relatively high cost, due to the difficulty in its production, specifically isolation and purification on a commercial scale with high yield and purity. Xylitol is generally prepared

from xylan-containing material, particularly hydrolysates of hemicelluloses through fermentation or chemical reactions. The recovery of xylitol from the fermentation broth or the reaction mixture is tedious.
US patent no. 4066711 discloses a method for preparing pharmaceutical grade xylitol from an aqueous solution containing mixtures of polyols including xylitol which comprises subjecting aqueous solution containing xylitol to concentration by evaporating water followed by crude crystallization and recrystallization of xylitol followed by the recovery of residual xylitol from the mother liquor by fractionating the solution using at least two columns of ion-exchange resin in two different metal ion forms. The purity of the xylitol crystals obtained through the process of said patent is more than 99.5% but at lower yields. However, the process involves multiple crystallization steps in combination with two ion exchange columns.
European patent application no. 1075795 discloses a process for producing xylitol of high purity (one-step desalting process) which comprises the steps of (1) removing the solid matter from a culture broth obtained by culturing a xylitol-producing microorganism in an aqueous culture medium, (2) desalting the resulting solid matter-removed culture broth by removing the ionic substances there from by means of a cation-exchange resin and an anion-exchange resin, (3) subjecting the resulting desalted solution to the chromatography using a strongly acidic cation-exchange resin to separate the xylitol from the other sugar alcohol(s) and sugar(s), and (4) obtaining the xylitol by separating it at a high purity from the resulting xylitol solution (fraction), and to a similar process (two-step desalting process) but wherein the desalting carried out twice by adding the ion-exclusion step between Steps (1) and (2) of the above-mentioned process, whereby most of the ionic substances are removed, by which processes highly pure xylitol can be obtained from a xylitol solution in the method for producing xylitol by using a xylitol-producing microorganism. However, the said method uses cation exchange and anion exchange methods atleast twice in addition to the ion-exclusion step and finally activated carbon treatment followed by concentration and crystallization resulting in a multistep procedure. Also the ion exclusion step requires large amount resins, consuming large amount of water and has low productivity. The whole process is carried out in aqueous medium. The overall process gives xylitol in high purity but at reduced yields.

US patent no, 4246431 discloses a method for recovering xylitol from the end syrups of the xylitol crystallization by subjecting the end syrup to chromatographic separation, whereby it is split into two or more fractions, the first fraction containing mainly the polysaccharides and the polysaccharide alcohols and subsequent fractions containing essentially the pentitols and hexitols. However, the method disclosed involves number of steps including chromatographic separation, acid hydrolysis, water evaporation and more to obtain xylitol in reduced yield.
US patent No. 7109005B2 or US 2002/0164731A1 discloses the process for simultaneous production of ethanol and xylitol, wherein ethanol of recovered by distillation followed by separation of xylitol using chromatography/membrane and crystallizing the xylitol from enriched solution at 65% recovery in the form of crude crystals. The chromatographic separation is carried out using sulphonated cation exchange resins which gives reduced recovery of the xylitol in impure form leading to loss of xylitol in crystallization step. The crude crystals were washed with water to obtain xylitol in 99.4% purity.
US patent 6538133B1 and EP 1075795A2 discloses the process for producing xylitol comprising removing solid matter from culture medium, desalting the culture broth by cation and anion exchange resin, performing chromatography using strong acid cation exchanger in calcium form for separation of xylitol, decolourization on active carbon, concentration and crystallization of xylitol from aqueous solution by cooling. The process also discloses the twice use of ion exclusion step after removal of solid matter and before desalting step. The process of this patent gives less than 70% recovery due to large number of steps as well as indicates more than 100% recovery across column filled with strong acid cation exchanger in calcium (example 1 and 3 wherein 43.125 gm input xylitol results in 44.28 gm of xylitol output across the column) which is scientifically impossible. The process does not disclose the use of membrane filtration for decolourization and/or purification, and hydrophobic interaction chromatography for separation of xylitol.
WO96/27029 or EP1019547B1 discloses method for recovering an organic compound from their solutions by crystallization by way of nucleation from solution having high viscosity and super-saturation and recovering the crystals formed. The process involves formation of crystals in super-saturated aqueous solution having high viscosity and later reducing the viscosity by adding solvent so as to ease out the filtration for recovering the crystals. The process does not disclose the use of crystallization in presence of solvent in improved and effective manner.

GB1236190A discloses process for manufacturing of xylose and xylitol, wherein the xylitol obtained after hydrogenation of purified xylose is filtered through cation exchange resin, concentrated and crystallized.
CN101538589A discloses the method for producing arabinose and xylitol involving fermentation, pre-treatment, nanofiltration. concentration, chromatography on simulated moving bed using ion exchange resins, further concentration and crystallization. Similarly CN 1736970A, CN1309626A, CN1284755C, CN1162348C, CN101628853A, CN101747148A, KR563394B1, GB1413032A, CA2075458C, AU752693B2, AU199941475A, AU662003B2, DE2961125D1, CA1083182A1, IE38959B1 US5158789A and 5139795A and CA996139A1 also discloses process for crystallization of xylitol from aqueous system with or without seeding and/or nucleation, melt crystallization etc. CA2332600A1, WO1999059426A3/A2/A1 and EP10800060B1 disclose crystallization of xylitol by contacting xylitol containing solution with particulate xylitol suspended in gas and drying the material to produce microcrystals.
US4066711A discloses the crystallization of major portion xylitol from aqueous solution and therein leaving mother liquor containing xylitol followed by removing xylitol crystals and recrystallizing xylitol from water to provide pure xylitol leaving mother liquor. Patent also discloses recovering xylitol from mother liquor1 by crystallization and recrystallization steps any subjecting at least portion of mother liquors to chromatographic fractionation using two column in series or parallel mode, one containing sulphonated cation exchange resin and another containing resin with A1+++ or Fe+++ form and followed by crystallization-recrystallization steps to yield xylitol. Similarly US4246431A discloses process for recovering xylitol from end syrups of xylitol crystallization characterized by subjecting the end syrup to chromatographic separation weakly cross-linked strongly acidic cation exchanger in calcium form. Xylitol crystals were obtained by cooling crystallization or precipitation-crystallization. Xylitol is recovered from mixed fraction by re-chromatographing the mixture followed by crystallization of xylitol from xylitol rich fraction. The process is complicated involving lot of reprocessing and does not give pure xylitol in one go. Also process does not involve any membrane filtration for separation or concentration of xylitol.
US6911565B2 discloses process for production of xylitol involving reducing and epimerizing ribulose to a mixture of ribitol, arabitol and xylitol; and chromatographically separating of a

xylitol-rich fraction by adsorption on ion exchange resin and chromatographic steps are recirculation into isomerisation and epimerization. Xylitol is recovered crystallized from aqueous fraction.
Gurgel et al. (Bioresource Technology, vol.52, 219-223. ]995) used both anion and cation exchange resins to purify xylitol from sugar cane bagasse hydrolysate fermentation broth, Xylitol had affinity for strong cation-exchange resin (Amberlite 200C) and weak anion-exchange resin (Amberlite 94S), which resulted in 40-55% loss of product because the xylitol adhered/adsorbed on the surface of the resin.
Wei et al (Front. Chem. Eng. China 2010, '4(1): 57-64) has described a process for purification and crystallization of xylitol from fermentation broth of corncob hydrolysates which includes the steps of decolorization by activated carbon, desalination by ion-exchange resins and separation from residual sugars. Pre-purified solution was concentrated under vacuum at 60 degree Celsius to reach supersaturation was mixed with ethanol (a water miscible solvent), stirred and kept for 48 hrs at - 20°C. The precipitated crystals were recovered by centrifugation or 0.45 micron filtration. In the process optimally 95% pure xylitol was obtained at xylitol crystallization yield of 60.2%. Further the process gave more than 98% purity at 45% recover;' ratio and less than 65% purity at above 95% recovery ratio indicating the need of re-crystallization/reprocessing and/or incorporation of additional steps to increase the yield of highly pure xylitol.
Rivas et al (J Agric Food Chem. 2006 Jun 14;54(12):4430-5) has described the process for purification of xylitol obtained by fermentation of corncob. The fermentation media was subjected to processing through sequential stages of charcoal adsorption, evaporative concentration, ethanol precipitation to precipitate a part of the proteins, uronic acids, ashes, and other nonvolatile compounds, evaporative concentration, and ethanol (a water miscible organic solvent) was added to reach 40-60% volume of the stream to allow crystallization at -10 or -5 °C. Under these conditions, 43.7% of food-grade xylitol xylitol contained in the initial fermentation broth was recovered in well-formed, homogeneous crystals with purity of 98.9%.

Affleck RP,(2000, thesis submitted to Virginia Polytechnic Institute and State University) discloses process for purification of xylitol from fermentation broth involving membrane separation, ion exchange purification, reverse osmosis or evaporation based concentration and crystallization steps. The said process gives xylitol in 90.3% purity with less than 90% recovery. Author also discloses that activated carbon treatment results into 60% loss of xylitol,
Thus none of the prior art teaches the process and sequence of operations/steps to yield xylitol in at least 95% yield and at least 98% purity without involving recrystallization, reprocessing, moth liquor processing and water for crystallization. Prior art discusses use of chromatographic separations using cation exchanger/ anion exchanger/ sulphonated strongly cation exchanger, and charcoal treatment/adsorption, but does not discloses the use of hydrophobic interaction or reverse phase chromatography which works on completely different scientific principles than ion exchange for separation and decolonization of xylitol. Prior art discloses the use of water miscible organic solvents for crystallization, leading to low/reduced recovery of xylitol in crystallization, but does not discloses the crystallization of xylitol from water immiscible/partially immiscible organic solvent. Thus, many of these techniques/processes in the prior art, such as the use of ion exchange adsorbent, activated carbon and multiple/ iterative crystallization, gives xylitol in required purity but in reduced yields and involves complex processes with recycles and reprocessing of impure streams.
Thus the prior art recognizes that there is techno-commercial problem associated with the recovery/ purification steps for obtaining xylitol in high yield and purity.
Therefore, there is a need for a process which can help in recovering the xylitol in high yield as well as high purity with minimum number of steps. The prior art also suggests that the use of activated carbon/ charcoal and iterative/ fractional crystallization results into heavy losses and hence affecting the economics of the process at commercial scale.
In the above context, the present invention discloses an efficient process for producing xylitol in high yield and high purity from crude feedstock in minimum number of steps. The said process produces a xylitol rich solution from which xylitol can be simply and efficiently recovered by crystallization in a single step, without resort to any extensive and expensive separation expedients. Generally, the xylitol can be purified by coupled membrane filtration

and chromatographic separation techniques and subsequently crystallized by using novel solvent system.
SUMMARY OF THE INVENTION
The present invention relates to a method for recovery of xylitol in high yield and purity from crude feedstock. The process of present invention involves removal of proteins, colouring matter, small and large molecular weight impurities and other polymeric impurities from crude feedstock by integrating/coupling membrane separation and chromatography followed by a single step crystallization of xylitol from war immiscible solvent system. The process of present invention gives xylitol in more than 98% purity with more than 95% yield.
DETAILED DESCRIPTION OF THE DRAWINGS
Figure 1 to 4 shows schematics of the process for recovery of xylitol in high yield and purity involving different hybrid processes in various coupled/integrated schemes.
DESCRIPTION OF INVENTION
The primary objective of the present invention is to recover xylitol in high yield and purity from crude feedstock in minimum number of steps.
It is further objective of the present invention is to achieve the recovery of the xylitol by employing integrated/coupled membrane separation, chromatography and crystallization techniques, wherein membrane separation and chromatography is integrated/coupled to make it hybrid step/process.
It is further objective of the present invention that to avoid the iterative / fractional crystallization and to reduce the number of steps involved in crystallization of xylitol.
It is an object of the present invention to achieve the crystallization of the xylitol in a single step with high yield and high purity.
It is an objective of the present invention to employ novel solvent system for crystallization of xylitol.

It is an objective of the present invention to reduce the time required for the crystallization of the xylitol.
For convenience, before further description of the present invention, certain terms employed in the specification, examples and appended claims are collected here. These definitions should be read in light of the remainder of the disclosure and understood as by a person of skill in the art. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by a person of ordinary skill in the art. The terms used throughout this specification are defined as follows, unless otherwise limited in specific instances.
The articles "a", "an" and "the" are used to refer to one or to more than one (i.e., to at least one) of the grammatical object of the article.
The terms "comprise" "comprising" "including" "containing" "characterized by" and grammatical equivalents thereof are used in the inclusive, open sense, meaning that additional elements may be included. It is not intended to be construed as "consists of only."
As used herein, "consisting of and grammatical equivalent thereof exclude any element, step or ingredient not specified in the claim.
The term 'hybrid process' refers to coupled or intergrated processes resulting in overall benefit to recovery of xylitol from crude feedstock.
The term 'negative hydrophobic interaction or reverse phase chromatography' is a process step wherein target product (i.e. xylitol) is recovered in flow through fraction.
The term ' 1-butanol' and 'n-butanoi' can be used interchangeably.
The term 'negative hydrophobic interaction' and 'reverse phase chromatography' can be used interchangeably.
The term 'hydrophobic adsorbent' and 'reverse phase adsorbent' and 'non ionic adsorbent' can be used interchangeably.
The present invention discloses a process for recovery of xylitol with high yield and purity from crude feedstock, comprising
a. Clarifying the crude feedstock by conventional means such as membrane filtration, centrifugation. sedimentation, flocculation, field flow fractionation, decantation or

combinations thereof for removal of insoluble matter and thereby to obtain a clarified feedstock;
b. Subjecting said clarified feedstock to a hybrid step consisting coupling of one or more
membrane filtration steps and negative hydrophobic interaction/reverse phase
chromatography in a sequence for decolourisation, removal of soluble small and large
molecular weight impurities and thereby recovering a xylitol containing fraction
substantially decolourized and free from impurities;
c. Concentrating the xylitol containing fraction obtained in step b, to syrupy mass by
conventional means such as nanofiltration. diafiltration. reverse osmosis, evaporation,
distillation or suitable combinations thereof;
d. Dissolving the syrupy mass into water immiscible/partially immiscible organic solvent
and thereby obtaining saturated solution of xylitol;
e. Subjecting said saturated solution of xylitol in water immiscible/partially immiscible
organic solvent to a temperature in range of+8 to -40 degree Celsius for period of at least
6 hrs to obtain xylitol crystals in single step;
f. Recovering said xylitol crystals by filtration or centrifugation;
g. Washing recovered xylitol crystals with organic or aqueous-organic solvent; and
h. Drying said xylitol crystals of step h to obtain xylitol in more than 95% overall yield and 98% purity.
The process of the present invention is performed in the sequence and involves following
steps:
a. Clarification of crude feedstock by conventional means such as membrane filtration,
centrifugation, sedimentation, flocculation, field flow fractionation, decantation or
combinations thereof for removal of insoluble matter to obtain a clarified feedstock;
b. Subjecting said clarified feedstock to negative hydrophobic/reverse phase
chromatography and thereby collecting a flow through/unadsorbed fraction containing
xylitol substantially free from proteins, colouring matter and other polymeric impurities;
c. Subjecting the flow through/unadsorbed fraction to membrane filtration for removal of
soluble large molecular weight impurities and thereby recovering the xylitol in
permeate/filtrate fraction;

d. Concentrating the permeate/filtrate fraction containing xylitol from step c to syrupy mass
by conventional means such as nanofiltration, diafiltration, reverse osmosis, evaporation,
distillation or suitable combinations thereof;
e. Dissolving the syrupy mass into water immiscible/partially immiscible organic solvent
and thereby obtaining saturated solution of xylitol;
f. Subjecting said saturated solution of xylitol in water immiscible/partially immiscible
organic solvent to a temperature in range of+8 to -40 degree Celsius for period of at least
6 hrs to obtain xylitol crystals in single step;
g. Recovering said xylitol crystals by filtration or centrifugation and washing recovered
xylitol crystals with organic or aqueous-organic solvent to obtain xylitol with more than
95% yield and 98% purity.
Preferably the process of the present invention is performed in the sequence and involves following steps:
a. Clarification of crude feedstock by conventional means such as membrane filtration,
centrifugation, sedimentation, flocculation, field flow fractionation, decantation or
combinations thereof for removal of insoluble matter to obtain a clarified feedstock;
b. Subjecting said clarified feedstock to membrane filtration for removal of soluble large
molecular weight impurities and thereby recovering the xylitol in permeate/filtrate
fraction;
c. Subjecting said permeate/filtrate fraction to negative hydrophobic/reverse phase
chromatography and thereby collecting a flow through/unadsorbed fraction containing
xylitol substantially free from proteins, colouring matter and other polymeric impurities;
d. Concentrating said flow through/unadsorbed fraction containing xylitol obtained from
step c to syrupy mass by conventional means such as nanofiltration, diafiltration, reverse
osmosis, evaporation, distillation or suitable combinations thereof;
e. Dissolving the syrupy mass into water immiscible/partially immiscible organic solvent
and thereby obtaining saturated solution of xylitol;
f. Subjecting said saturated solution of xylitol in water immiscible/partially immiscible
organic solvent to a temperature in range of +8 to -40 degree Celsius for period of at least
6 hrs to obtain xylitol crystals in single step;

g. Recovering said xylitol crystals by filtration or centrifugation and washing recovered xylitol crystals with organic or aqueous-organic solvent to obtain xylitol with more than 95% yield and 98% purity.
Alternatively the process of the present invention is performed in the sequence and involves following steps:
a. Clarification of crude feedstock by conventional means such as membrane filtration,
centrifugation, sedimentation, flocculation, field flow fractionation, decantation or
combinations thereof for removal of insoluble matter to obtain a clarified feedstock;
b. Subjecting said clarified feedstock to membrane filtration for removal of soluble large
molecular weight impurities and thereby recovering the xylitol in permeate/filtrate
fraction;
c. Subjecting said permeate/filtrate fraction to another membrane filtration for removal of
soluble small molecular weight impurities including salts and thereby recovering the
xylitol in retentate fraction;
d. Subjecting said retentate fraction to negative hydrophobic/reverse phase adsorptive
chromatography and thereby collecting a flow through/unadsorbed fraction containing
xylitol substantially free from proteins, colouring matter and other polymeric impurities;
e. Concentrating said flow through/unadsorbed fraction containing xylitol obtained from
step c to syrupy mass by conventional means such as nanofiltration, diafiltration, reverse
osmosis, evaporation, distillation or suitable combinations thereof;
f. Dissolving the syrupy mass into water immiscible/partially immiscible organic solvent
and thereby obtaining saturated solution of xylitol;
g. Subjecting said saturated solution of xylitol in water immiscible/partially immiscible
organic solvent to a temperature in range of+8 to -40 degree Celsius for period of at least
6 hrs to obtain xylitol crystals in single step;
h. Recovering said xylitol crystals by filtration or centrifugation and washing recovered xylitol crystals with organic or aqueous-organic solvent to obtain xylitol with more than 95% yield and 98% purity.

Unlike the processes disclosed in the prior art the present invention has employed a novel approach for removal of the impurities such as proteins, colouring matter, small and large -molecular weight impurities, salts and other polymeric impurities by the integration/coupling of membrane and chromatographic separation techniques. Also unlike the processes disclosed in prior art the process of present invention involves negative or flow through hydrophobic/reverse phase chromatography wherein the proteins, colouring matter and other polymeric impurities adsorbs on the adsorbent and xylitol remains in flow through/unadsorbed fractions. This integrated approach allows the recovery of the xylitol in reduced number of steps, in reduced time, at high productivity, and thereby making it cost-effective and industrially adaptable. Furthermore, due to the integrated approach and reduced number of steps, the loss of xylitol is minimum.
Finally the xylitol from the end syrup is crystallized by novel solvent system in a single step to yield high purity (more than 98%) xylitol crystals. The crystallization can optionally be effected by addition of pure crystals of xylitol as a seed. Xylitol is recovered from the fermentation broth in more than 95% yield.
Another embodiment of the present invention provides for a process for recovery of xylitol with high yield and purity from crude feedstock wherein the concentration of xylitol in crude feedstock is in the range of 0.1-100 %.
According to one of the embodiments of the present invention, the crude feedstock may be the hydrolysates of different xylan rich plants/trees such as birch and beech. It may also include the hydrolysates of the lignocellulosic materials including but not limited to straw, bagasse, cotton stalk or cotton seed hulls, oat hulls, corn cobs and stalks. It may also contain extract of various fruits and vegetables including but not limited to carrot, onion, spinach, white mushroom, eggplant, cauliflower, strawberry, yellow plum. These feedstock's may be directly used for production of xylitol or xylitol containing feedstock's through appropriate chemical, enzymatic, fermentation process/es or combinations thereof.
Alternatively, crude xylitol containing feedstock can be obtained from chemical or microbial reduction of D-xylose, ribulose. or hydrolysates of xylan-rich hemicellulosic materials. A number of microorganisms that possess the enzyme xylose reductase can produce xylitol by fermentative conversion of D-xylose to xylitol. Thus, crude feedstock of xylitol can be obtained from some yeasts including but not limited to Candida pelliculosa, Candida

boidinii, Candida guilliermondii, and Candida tropicalis. Bacteria species can also be the source of crude feedstock, those includes but not limited to Enterobacter liqufaciens, Corynebacterium sp., and Mycobacterium smegmatis.
Some species of fungi can also be the source for crude feedstock, those includes but not limited to Penicillium, Aspergillus, Rhizopus, Glicoladium, Byssochlamyz, Myrotnecium, and Neurospora sp.
One of the embodiments of the present invention provides a process for recovery of xylitol with high yield and purity from crude feedstock wherein the said membrane has molecular cut off of at least 150 Dalton and the large portion of xylitol is recovered in permeate/filtrate fraction.
Yet in similar embodiments of the present invention provides a process for recovery of xylitol with high yield and purity from crude feedstock wherein the said membrane has molecular cut off in the range of 50 to 200 Dalton and the large portion of xylitol is recovered in retentate fraction.
In the above embodiments of the present invention the xylitol recovered in either permeate or retentate is substantially free from small and large molecular weight impurities and the said step also performs the decolourization.
According to one of the embodiments of the present invention, the membrane/s used for filtration used can be porous and in the form of module such as but not ffmited to hollow fiber, tubular, flat sheet, spiral membrane based on polyether sulfone, cellulose acetate, regenerated cellulose, nylon, polytetrafluoroethylene (PTFE), stainless steel, ceramic. cellulose acetate phthalate or combination thereof. In the preferred embodiment of present invention the cross flow type of membranes are used to avoid concentration polarization effect.
Another embodiment of the present invention provides a process for recovery of xylitol with high yield and purity from crude feedstock wherein the said negative chromatographic separation is carried out by using hydrophobic interaction, reverse phase polymeric adsorbents or non ionic adsorbent.

Yet another embodiment of the present invention provides for a process for recovery of xylitol with high yield and purity from crude feedstock wherein the said adsorbent matrix is capable of adsorbing /retaining proteins, colouring matter, small and large molecular weight impurities, salts, and other polymeric impurities from the crude feedstock, and comprising one or more of following: (i) a non sulfonic resin (ii) non ionic resin (iii) having a surface and/or surface group, which has interacting ability with impurities, (iv) non ion exclusion chemistry, (v) which is rigid and porous, (vi) in the form of a membrane, (vii) has synthetic or natural polymeric base matrix, (viii) has a synthetic base matrix of polystyrene, divinylbenzene (PSDVB), polymethacrylates, polyacrylamide and the like, (ix) has natural polymeric base matrix of agarose, cellulose, chitosan, dextran and the like, (x) is crosslinked, (xi) a modified silica with aromatic and/or aliphatic moiety as substituted group having CI to C30 carbon atoms, (xii) has interacting group which is a part of base matrix, (xiii) has interacting group grafted on the base matrix by known activation chemistry, (xiv) the said interacting group is unsaturated or saturated aliphatic and/or an aromatic moiety of a C1-C30 carbon molecules, (xv) has the interacting group is halogen atom, (xvi) the interacting group is cyano, diol or amino, (xvii) has the interacting group which has different interacting ability for xylitol and colouring matter and other impurities, (xviii) microporous, macroporous, mesoporous, gigaporous, supermacroporous or throughporous, (xix) a mixed mode based on one or more than one of a synthetic or natural polymeric matrix and having amino (primary. secondary or tertiary) or imino moiety, (xx) a matrix based on one or more of a polymer comprising PSDVB, polymethacrylates, polyacrylamide, a natural polymer and combinations thereof having hydroxyl or diol group, (xxi) a hydrophobic group.
One of the embodiments of the present invention provides for a process for recovery of xylitol with high yield and purity from crude feedstock wherein combined result of membrane filtration and chromatographic separation is at least 92% decolourization of the crude feedstock.
Another embodiment of the present invention provides a process for recovery of xylitol with high yield and purity from crude feedstock wherein the process is carried out in one or more of a mode comprising in single or in multiples or a combination of a batch mode, a continuous mode, an expanded bed, a fluidized bed, a liquid solid circulating fluidized bed (LSCFB), a simulated moving bed (SMB), a moving bed, an improved simulated moving bed (ISMB), a centrifugal chromatography, an annular chromatography; chromatography being

preferably performed with a packed bed chromatographic column or expanded bed chromatographic column, which comprises packing the column with a suitable adsorbent and passing the said crude feedstock and mobile phase/s through the column.
In another embodiment of the present invention provides for a process for recovery of xylitol with high yield and purity from crude feedstock wherein concentration of decolourized and separated xylitol is carried out using conventional means such as but not limited to membrane filtration, evaporation, distillation or combinations thereof.
In another embodiment of the present invention provides for a process for recovery of xylitol with high yield and purity from crude feedstock wherein concentration of decolourized and separated xylitol is carried out using combination of nanofiltration/reverse osmosis and evaporation/distillation.
One of the embodiments of the present invention provides for a process for recovery of xylitol with high yield and purity from crude feedstock wherein the said organic solvent for crystallization is selected from a group comprising of water immiscible organic solvents but not limited to n-butanol, chloroform, methylene dichloride, isobutanol, ethyl acetate, butyl acetate, methyl isobutyl ketone or any suitable combinations thereof.
One of the preferred embodiments of the present invention provides for a process for recovery of xylitol with high yield and purity from crude feedstock wherein the organic solvent used for crystallization of xylitol is n-butanol.
Another embodiment of the present invention provides for a process for recovery of xylitol with high yield and purity from crude feedstock wherein the syrupy mass is heated at a temperature of about 30-100°C and n-butanol is added to the heated syrupy mass.
Another embodiment of the present invention provides for a process for recovery of xylitol with high yield and purity from crude feedstock wherein pure crystals of xylitol are added as seeds to the syrupy mass before or after addition of n-butanol.
Another embodiment of the present invention provides for a process for recovery of xylitol with high yield and purity from crude feedstock wherein the temperature for crystallization of xylitol from water immiscible organic solvent solution to obtain high yield and high purity xylitol is in the range of+8 to -40°C.

One of the preferred embodiments of the present invention for a process for recovery of xylitol with high yield and purity from crude feedstock wherein the temperature for crystallization of xylitol from water immiscible organic solvent solution to obtain high yield and high purity xylitol is in the range of 0 to -20°C.
One of the embodiments of the present invention provides for a process for recovery of xylitol with high yield and purity from crude feedstock wherein the aging time is for crystallization of xylitol from water immiscible organic solvent solution to obtain high purity xylitol is in the range of 6 to 48 hrs.
One of the preferred embodiments of the present invention provides for a process for recovery of xylitol with high yield and purity from crude feedstock wherein the crystallization is assisted by ultrasound or sonication for improving the performance of crystallization in terms of yield, purity and time (aging time) of crystallization. In an embodiment the crystallization time is in the range of 6 to 24 hrs.
Yet in another embodiment of the present invention provides for a process for recovery of xylitol with high yield and purity from crude feedstock wherein the aging time is for crystallization of xylitol from water immiscible organic solvent solution to obtain high purity xylitol is in the range of 12 to 36 hrs
One of the preferred embodiments of the present invention provides for a process for recovery of xylitol with high yield and purity from crude feedstock wherein whenever it is necessary crystals washing can be done with non polar solvents after recovery of xylitol crystals by conventional means such ass but'not limited to filtration, centrifugation or combinations thereof like using basket centrifuge, agitated noose filter dryer etc.
One of the preferred embodiments of the present invention provides for a process for recovery of xylitol with high yield and purity from crude feedstock wherein the said washing solvent is selected from a group comprising of but not limited to n-butanol, iso-butanol, 1.3-propanediol, hexane, heptane, dodacane, octane, nonane or combinations thereof.
Another embodiment of the present invention provides for a process for recovery of xylitol with high yield and purity from crude feedstock wherein the organic solvent can be reused as such or after clarification by passing through charcoal or chromatographic adsorbents or by

recovery through other conventional methods such as but not limited to distillation, evaporation, membrane filtration or combinations thereof.
Another embodiment of the present invention provides for a process for recovery of xylitol with high yield and purity from crude feedstock wherein the adsorbent used in negative hydrophobic interaction/reverse phase chromatography is regenerated and reused in the process. In the said embodiment the regeneration of adsorbent is carried out using water. organic solvent, acids, alkali, salts or suitable combinations thereof.
In the above embodiment of the present invention the regeneration of adsorbent is carried out using organic solvent such as but not limited to methanol, ethanol, isopropanol, acetonitrile, dimethyl formamide, dimethyl sulfoxide, ter-butanol, butanol or combinations thereof.
In the above embodiment of the present invention the regeneration of adsorbent is carried out using acids such as but not limited to acetic acid, hydrochloric acid, sulphuric acid, nitric acid, citric acid and combinations thereof.
In the above embodiment of the present invention the regeneration of adsorbent is carried out using alkalis such as but not limited to sodium hydroxide, potassium hydroxide, ammonia, ammonium hydroxide, calcium hydroxide, ethylene diamine, triethyl amine and combinations thereof
In the above embodiment of the present invention the regeneration of adsorbent is carried out using salts or combination of salts with acid, alkali, organic solvent and is selected from group but not sodium chloride, potassium chloride, sodium acetate, potassium acetate, sodium phosphate, potassium phosphate, ammonium acetate, ammonium phosphate, ammonium chloride, calcium chloride and combinations thereof.
Xylitol purified using process of present invention can be used in the food, pharmaceutical, neutraceuticals industry as a sugar substitute, in medicinal applications like it is used as sweetener for diabetes patient (as it is used in osteoporosis as it actually improves bone density and in ear and upper respiratory infection). Xylitol produced by process of present invention can be used to increase the activity of neutrophils, the white blood cells involved in fighting many bacteria and to control oral infections, and also in dental health benefits like in caries prevention.

Advantages and salient features of the process of the present invention are
1. Unlike the processes disclosed in the prior art the present invention has employed a novel approach by the integration/coupling of membrane filtration and negative chromatographic separation techniques. Employing membrane separation for removal of proteins and coloring impurities. Further the present invention involves negative or flow through hydrophobic interaction/reverse phase chromatography wherein remaining proteins, colouring matter and other polymeric impurities adsorbs on the adsorbent and xylitol remains in unadsorbed/flow through fractions. This integrated approach allows the recovery of the xylitol in reduced number of steps and minimal loss of xylitol making it cost-effective and industrially adaptable.
2. Application of novel solvent system for xylitol crystallization from the end syrup in a single step to yield high purity (>98%) xylitol crystals in high yields
3. One of the major advantages of the present invention is to avoid the iterative / fractional crystallization and to reduce the number of steps involved in crystallization of xylitol.
4. The process of present invention can be used for recovery of sugars, sugar alcohols, polyalcohols and mixtures thereof.
The present invention is further described by, but not limited to, the following examples.
Example 1: Membrane filtration of clarified crude feedstock
Crude feedstock containing 200 gm/L xylitol was subjected to the removal of suspended particle by the means of centrifugation. The clarified crude feedstock containing xylitol was collected and different membranes were evaluated for the removal of soluble larger and small molecular impurities. Each membrane was initially washed with DI water. 500 ml of partially clarified crude feed stock was passed through the membranes having the different MWCO. At the end of the filtration permeate and retentate was collected from each membrane. Xylitol recovery and percent decolourization were calculated for each membrane (Table 1).
Table 1: Performance of different membrane for xylitol recovery and decolourization

Membrane filtration Average Xylitol
Serial Decolourization
type MWCO Fraction recovery
no (%)
membrane (%)

1
N anofiltrati on/reverse osmosis 50 Dalton Retentate 100 2

Permeate 0 -
2 Nano filtratio n/reverse osmosis l00 Dalton Retentate 99 5

Permeate 1 -
3 Nanofiltration/reverse osmosis 150 Dalton Retentate 96.5 15

Permeate 3.5 -
4 Nanofiltration 300 Daltons Permeate 90 76.8
5 Nanofiltration 500 Dalton Permeate 99.4 82
6 Ultrafiltration lkD Permeate 99.6 78
7 Ultrafiltration 3kD Permeate 99.8 75
8 Ultrafiltration 5kD Permeate 99.8 58
9 Ultrafiltration lOkD Permeate 99.7 34
10 Ultrafiltration 100 kD Permeate 99.8 30
11 Ultrafiltration 500 kD Permeate 99.8 18.5
12 Microfiltration O.lμ Permeate 99.9 14
13 Microfiltration 0.6 μ Permeate 99.9 12
14 Microfiltration 0.8 μ Permeate 99.9 7
15 Microfiltration 1μ Permeate 99.9 5
16 Microfiltration 3μ Permeate 100 2
In the case of membranes having the MWCO in the range of 50-200, most of the xylitol is recovered in the retentate fraction, while in the case of membranes having MWCO of at least 150 dalton, xylitol is recovered in permeate fraction moreover membranes having MWCO in the range of 500 dalton to 3 kD shows minimum 70% of crude feedstock decolourization with more than 99.5% of xylitol recovery in permeate fraction.
Example 2: Negative hydrophobic interaction/reverse phase chromatography
Crude feedstock containing xylitol 200 gm/L was subjected to the removal of suspended particle by the means of microfiltration and the clarified crude feedstock containing xylitol was collected permeate fraction. The clarified feedstock was then processed using different nt adsorbents packed in a column of dimensions, 2.5 cm diameter x 25 cm length. Properties of adsorbents are shown in Table 2. 122 ml of each test adsorbent previously washed with methanol and DI water was packed in preparative column. 500 ml of clarified crude

feedstock was loaded from the top of column with the help of peristaltic pump at the flowrate of 2 bed volumes/hour. The flow through/unadsorbed fractions were collected from each resin column. The flow through fraction was subjected to analysis for xylitol using Aminex 87H column (BioRad, USA) and recovery and percent decolourization was calculated as shown in Table 3.
Table 2; Properties of the adsorbents

Sr.
No. Resins Avg. Particle size (μm) Pore
radius (A0) Type of adsorbent Base matrix
1 Sepabeads SP700 250 105 Nonionic/reverse phase PSDVB
2 Diaion HP20 250 260 Nonionic/reverse phase PSDVB
3 Sepabeads SP70 250 70 Nonionic/reverse phase PSDVB
4 Sepabeads SP20ss 75 90 Nonionic/reverse phase PSDVB
5 Diaion HPA
25 260 300 Anion exchanger PSDVB
6 Diaion HPA
75 260 300 Anion exchanger PSDVB
7 Diaion HP2MG 250 300 Nonionic/reverse phase polymethacryalte
8 Tulsion T-42 300 280 Strong cation exchanger PSDVB
9 Celbeads 400 3000 Nonionic/reverse phase Cellulose
10 Indion PA600 350 300 Nonionic/reverse phase PSDVB
11 Indion PA500SS 80 300 . Nonionic/reverse phase PSDVB
12 Diaion UBK 530 ~ ~ Sulphonated cation PSDVB
13 Diaion UBK 530 — ~ Sulphonated cation in calcium form PSDVB
Table 3 Adsorbent performance for xylitol recovery and decolourization

Sr.
No. Adsorbents Decolourization (%) Xylitol recovery (%)
1 Sepabeads SP700 94 99.2

2 DiaionHP20 92.4 99.7
3 Sepabeads SP70 93.5 99.9
4 Sepabeads SP20ss 95.2 99.1
5 Diaion HPA 25 71.3 62.5
6 Diaion HPA 75 72.6 64.4
7 Diaion HP2MG 84.2 82.4
8 Tulsion T-42 85.2 72.2
9 Celbeads 99.8 93.6
10 Indion PA600 99.9 95.2
11 Indion PA500SS 100 94.4
12 Diaion UBK 530 55.6 76.5
13 Diaion UBK 530 in calcium form 48.2 68.5
Flow through fractions collected from the columns containing hydrophobic interaction/ reverse phase/nonionic adsorbents shows more than 90% of decolourization with more than 98% recovery of xylitol. Ionic adsorbents show less than 75% decolourization with less recovery than nonionic adsorbents because xylitol shows adsorption on the ionic adsorbent. In case of the hydrophobic interaction/reverse phase/nonionic adsorbent xylitol is recovered in flow through fraction which is substantially free from colouring impurities, hence negative hydrophobic interaction/reverse phase chromatography is carried out present invention.
Example 3: Coupling/integration membrane filtration and negative hydrophobic interaction/reverse phase chromatography
Crude feedstock is clarified using microfiltration and the clarified feedstock is used for carrying out separation and decolourization of xylitol. Clarified crude feedstock containing 220 gm/L of xylitol was subjected to different sequences in a hybrid process involving coupling/integration of membrane filtration and negative hydrophobic interaction/reverse phase chromatography. Membranes and adsorbents were selected from the results obtained from example 1 and example 2. From example 1, membranes having MWCO of 200 dalton to 1 kD was selected and from example 2 PSDVB based adsorbent was selected for designing hybrid process. Xylitol containing fraction was collected from every hybrid process and was subjected to analysis to determine xylitol recovery and % decolourization (Table 4).

Table 4: Hybrid processes for separation and decolourization of xylitol from clarified feedstock

Sr.
No. Coupling/integration
sequence of processes in
hybrid process Adsorbent/membrane average MWCO Xylitol recovery
(%) Decolourization (%)
1 Chromatography Sepabeads SP700 98.2 98 01
Membrane filtration 500-Dalton

? Membrane filtration 500 Dalton 98.4 98 2
Chromatography Sepabeads SP700

3 Chromatography Sepabeads SP700 98.5 98 3
Membrane filtration lkD

4 Membrane filtration lkD 98.8 98 7
Chromatography Sepabeads SP700

5 Chromatography Sepabeads SP700 98.1 95 6
Membrane filtration 150daltons

Membrane filtration lkD 98.7
6 Membrane filtration lOO.daltons
99.1
Chromatography Sepabeads SP700

Membrane filtration lkD 98.1 98.2
7 Membrane filtration 100 daltons

Chromatography Indion PA600

8 Membrane filtration lkD 98.5 98.3
Chromatography Indion PA 1200

Hybrid process involving coupling/integration of membrane filtration and negative hydrophobic interaction chromatography shows more than 98% of xylitol recovery and decolonization irrespective of the sequence of the operation. Hence this approach results into the fraction containing xylitol substantially free from impurities.
Example 4: Single step crystallization of the xylitol

About 10 L of fraction crude feedstock was clarified using 0.2 micron microfiltration and clarified feedstock containing 185.2 gm/L of xylitol was charged to the hybrid process consisting ultrafiltration membrane of MWCO 1 kD coupled with chromatographic column packed with Sepabeads SP700. The permeate fraction of ultrafiltration was continuously charged to hydrophobic interaction/reverse phase chromatography column and flow through fraction was continuously collected. About 98.78% of xylitol was recovered after hybrid process. The decolourization efficiency was found to be 98.45%. The flow through fraction was then concentrated using nanofiltration on 100 dalton membrane to obtain xylitol in retentate fraction with 98.6% recovery. The concentration of xylitol in retentate was 455.4 gm/L. This mass was then divided into eight equal portions and further separately concentrated using evaporation under vacuum at 55±5 degree Celsius to form complete syrupy mass. Flask containing syrupy mass was kept on water bath 55±5°C; different water immiscible solvents (Table 5) were added to the syrupy mass to obtain saturated solution of xylitol in each solvent. To one of the syrupy mass water miscible solvent i.e. ethanol was added to obtain saturated solution. The saturated solvent layer was then separately transferred to the glass reactor and to that finely ground standard xylitol (1.0g/l) was added in order to favour nucleation of the crystals. The glass reactors were kept at different cooling temperature and incubation time (Table 5). At the end of crystallization cycle, xylitol crystals were recovered from all the glass reactors by filtration on 0.2 micron filter and crystals were washed with 150 ml of hexane. The recovered crystals were dried at the temperature not exceeding 100 degree Celsius for 5 hrs. Crystallization yield and purity of crystals with the different solvents was calculated (Table 5).
Table 5: Crystallization of xylitol

Sr.
No Solvent Cooling
temperatu
re
(°C) Time of
incubation
(hrs) Optimum
temperature
range determined
(°C) Optimum incubation
time
(hrs) Crystallization
yield (%) Assay
Purity
(%)
1 Isobutanol 4 to -40 4-48 0 to -25 12-45 25.6 92.1
2 Ethyl acetate 4 to -40 4-48 Oto-25 12-36 72.4 88.4
3 Butyl acetate 4 to -40 4-48 0 to -28 12-36 77.2 89.9
4 Methylene dichloride 4 to -40 4-48 0 to -32 12-36 73.5 80.1
5 Cyclohexane 4 to -40 4-48 0 to -22 12-40 85.8 96.3

6
Carbon
disulfide 4 to -40 4-48 0 to -30 12-36 61.3 84.5
7 1-butanol 4 to -40 4-48 0 to -20 12-36 98.1 99.7
8 Ethanol 4 to -40 4-48 0 to -35 24-48 58.2 98.2
More than 98 % of xylitol crystallization recovery was found with 1-butanol solvent, where crystallization was preferably carried out at -20 ° C for 36 hrs. Xylitol crystals obtained with 1-butanol were washed with 150 ml of hexane. Crystals were dried completely at temperature at temperature below 60° C. Residual 1-butanol and hexane level was below the acceptable limit. Crystals were analyzed and found to be having the assay purity of more than 99%.
Example 5: Effect of crude feedstock concentration
Clarified fraction containing various concentrations of xylitol was processing as described in example 1, 2, 3 and 4 with optimum parameters. The results on yield and purity are given in Table 6. For high concentrations clarified feedstock is processed using ultrafiltration coupled with chromatography and for low concentration feedstocks were processed using ultrafiltration, nanofiltration and chromatographic steps of hybrid process.
Table 6: Assay purity and recovery of xylitol obtained from crude feedstock with different
concentrations.

Sr. No. Initial xylitol concentration (gm/L) Crystal assay purity (%) Crystallization yield (%)
1 10.6 98.2 97.6
2 28.2 99.8 98.5
3 85.1 99.7 98.2
4 100.6 98 98.6
5 135.8 98.6 96.9
6 185.4 99.5 98.2
7 268.9 98.7 96.2
8 460.6 98.8 97.5
Example 6: Recovery of xylitol from crude feedstock
2800 ml of clarified crude feedstock containing xylitol (concentration: 20.1%) was subjected to ultrafiltration on lkD membrane and permeate fraction was charged to the negative

hydrophobic chromatography for removal of hydrophobic and colouring impurities, proteins etc. Preparative column was packed with 1000 ml of adsorbent, Indion PA600. Flow through fraction containing xylitol was collected. Flow through fractioned 99,5% of xylitol recovery with 98.2% of colour removal. The flow through fraction containing xylitol 168.2 gm/L was concentrated to syrupy mass by evaporation at 55±5° C and xylitol was crystallized by addition of 1-butanol. Flask containing syrupy mass was kept on water bath 55±5°C; 1-butanol was added to the syrupy mass to obtain saturated solution of xylitol in solvent. To that finely ground standard xylitol (1.0g/l) was added in order to favour crystallization/nucleation of the crystals. This was then was subjected to at -20 ° C for 36 hrs for gaining and crystals growth. Xylitol crystals were filtered and washed with 500 ml of hexane. Crystals were dried completely at 40° C for 10 hrs. Residual 1-butanol and hexane level was below the acceptable limit. Crystals were subjected to assay purity analysis, This coupled process yield the crystal having the assay purity of 99.12% with recovery of more to obtain 533.23 gm of xylitol (i.e. 98.3%)
Example 7: Recovery of xylitol from fermentation broth
The crude fermentation broth containing 19.8 % of xylitol is clarified by centrifugation at 15000 rpm. The clarified feedstock is initially passed through a chromatographic column containing Sepabeads SP700 by adjusting the flow rate to 1ml /min. The flow through fractions containing xylitol are collected and subjected to ultrafiltration using a membrane with a MWCO lKDa. The permeate fraction containing xylitol is concentrated by means of evaporation under vacuum at 50 degree Celsius to obtain a syrupy mass. Xylitol is crystallized from syrupy mass using 1-butanol, crystals were filtered to obtain xylitol in 95% yield and 98.8% purity.
Example 8: Recovery of xylitol from fermentation broth
2.0 L of crude feedstock containing 10% of xylitol is clarified by centrifugation at 15000 rpm. The clarified feedstock is initially subjected to ultrafiltration using a membrane with a MWCO lKDa. The permeate fraction containing xylitol is passed through a chromatographic column containing Sepabeads SP70 by adjusting the flow rate to 1.0 ml /min. The flow through fractions containing xylitol were collected and concentrated by means of nanofiltration on 100 dalton membrane followed by distillation under vacuum at 55 degree Celsius to obtain a syrupy mass. Xylitol is crystallized from syrupy mass using 1-butanol and

crystals were filtered, washed with hexane and dried at 45 degree Celsius for 10 hrs to obtain xylitol in 96.8% yield and 99.2% purity.
Example 9: Recovery of xylitol from fermentation broth
1.0 L of the xylitol containing crude feedstock was processed as described in example 6, whit the change that the crystallization was further assisted by ultrasonication or ultrasound. The crystallization was completed in 8 hrs and about 98.9% xylitol was recovered with 99.7% purity.
Example 10: Recover)' of xylitol from fermentation broth using continuous chromatography
The process for recovery of xylitol was carried out as described in example 6, wherein the negative hydrophobic interaction/reverse phase chromatography is carried out in continuous manner using continuous countercurrent fluidized moving bed. The process has resulted in 98.3% recovery of xylitol with 99.4% assay purity,

I/We claim:
1. A process for recovery of xylitol in high yield and purity from crude feedstock, the process
comprising,
a. Clarifying the crude feedstock by conventional means to obtain a clarified
feedstock;
b. Subjecting said clarified feedstock to a hybrid process comprising the coupled
sequence of one or more steps of membrane filtration and negative hydrophobic
interaction or reverse phase chromatography for decolourisation, removal of
soluble small and large molecular weight impurities and thereby recovering a
xylitol containing fraction substantially decolourized and free from impurities;
c. Concentrating said xylitol containing fraction obtained in step b to syrupy mass
by conventional means;
d. Dissolving the syrupy mass into water immiscible or partially immiscible organic
solvent and thereby obtaining saturated solution of xylitol;
e. Crystallizing said saturated solution of xylitol at a temperature in range of+8 to -
40 degree Celsius for period of at least 6 hrs to obtain xylitol crystals in single
step;
f. Recovering said xylitol crystals by filtration or centrifugation;
g. Washing recovered xylitol crystals with organic or aqueous-organic solvent; and
h. Drying said xylitol crystals of step h to obtain xylitol in more than 95% overall
yield and 98% purity.
2. The process as claimed in claim 1, wherein the concentration of the xylitol in the crude feedstock is in the range of 0.1-100 %.
3. The process as claimed in claim 1, wherein the hybrid process comprises coupled sequence of micro filtration, ultrafiltration and negative hydrophobic interaction chromatography.
4. The process as claimed in claim 1, wherein the hybrid process comprises coupled sequence of microfiltration, ultrafiltration nanofiltration and negative hydrophobic interaction chromatography.
5. The process as claimed in claim 1, wherein the hybrid process comprises coupled sequence of microfiltration, negative hydrophobic interaction chromatography and ultrafiltration.
6. The process as claimed in claim 1, wherein the xylitol containing fraction from step b is concentrated by means of membrane filtration, wherein membrane filtration can be. nanofiltration or reverse osmosis, evaporation, distillation or combinations thereof.
7. The process as claimed in claim 1, wherein the xylitol containing fraction from step b is concentrated by nanofiltration followed by evaporation or distillation.

8. The process as claimed in claim 1, wherein the said membrane filtration has membrane molecular weight cut off (MWCO) in the range of 50 to 200 Daltons, wherein xylitol is concentrated and recovered in retentate fraction.
9. The process as claimed in claim 1, wherein the said membrane filtration has membrane with molecular weight cut off (MWCO) is at least 150 Daltons, wherein xylitol is recovered in permeate fraction.
10. The process as claimed in claim 1, wherein the negative hydrophobic interaction chromatography is carried out using non-ionic adsorbents.
11. The process as claimed in claim 1, wherein the non-ionic adsorbents has a base matrix selected from group consisting of polystyrene, polystyrene divinylbenzene (PSDVB), acrylic acids, methacrylate, methylmethacryaite, polymethacryalte, acryalamide, agarose, cellulose, silica, chitin, chitosan, dextran, titanium dioxide, stainless steel or combinations thereof
12. The process as claimed in claim 1, wherein the non-ionic adsorbents has base matrix preferably consisting of polystyrene divinylbenzene (PSDVB) or polymethacryalte with average particle size of at least 5 micron and average pore size of at least 60 Angstroms
13. The process as claimed in claim 1, wherein the non-ionic adsorbents has base matrix of polystyrene divinylbenzene (PSDVB) with average particle size of 300 micron and average pore size of 105 Angstroms
14. The process as claimed in claim 1, wherein the negative hydrophobic interaction chromatography is carried out in batch, semi-continuous or continuous mode using stirred tank or columns.
15. The process as claimed in claim 1, wherein membrane filtration and negative hydrophobic interaction chromatography together results in at least 90% decolourisation of the crude feedstock.
16. The process as claimed in claim 1, wherein the said water immiscible or partially immiscible organic solvent is selected from a group consisting of n-butanol, chloroform, methylene dichloride, isobutanol, ethyl acetate, butyl acetate, methyl isobutyl ketone or combinations thereof.
17. The process as claimed in claim 1, wherein the said water immiscible or partially immiscible organic solvent is n-butanol.
18. The process as claimed in claim 1, wherein the saturated solution of xylitol is subjected to a temperature preferably in the range of 0 to -20°C.
19. The process as claimed in claim 1, wherein organic or aqueous-organic solvent for washing of the recovered xylitol crystals is selected from a group consisting of hexane, heptanes, cyclohexane, carbon disulfide, n-butanol, chloroform, methylene dichloride, isobutanol, ethyl acetate, butyl acetate, methyl isobutyl ketone or combinations thereof.
20. The process as claimed in claim 1, wherein organic or aqueous-organic solvent for washing of the recovered xylitol crystals is hexane.
21. The process as claimed in claim 1, wherein drying of xylitol crystals is carried out at temperature not exceeding 100 degree Celsius.

22. The process as claimed in claim 1 wherein the water immiscible or partially immiscible organic solvent is recovered and recycled after recovery of the xylitol crystals.
23. The process as claimed in claim 1 and 10 wherein the non ionic adsorbents are regenerated and reused for the process
24. The process as claimed in claim 1, wherein the crystallization of xylitol is assisted by ultrasound/sonication