FR2521569A1 - PROCESS FOR DEPOLYMERIZING A POLYSACCHARIDE HAVING A HELICOIDAL STRUCTURE IN A STICK - Google Patents

Abstract

PROCESS RELATING TO THE DEPOLYMERIZATION OF A POLYSACCHARIDE HAVING A HELICOIDAL STRUCTURE IN STICKS. THIS PROCESS INCLUDES A STEP WHICH CONSISTS OF FORCING A SOLUTION OF POLYSACCHARIDE IN A SOLVENT (SOLVENT A) THROUGH A CAPILLARY WITH A HIGH SHEAR RATE, IN ORDER TO PRODUCE A DEGRADED POLYSACCHARIDE WITH LOWER MOLECULAR WEIGHT, WHICH HAS EVEN A PERIOD OF PERIOD. THE SAME HELICOIDAL STRUCTURE AS THOSE OF THE ORIGINAL POLYSACCHARIDE.

Description

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  The present invention relates to the specific depolymerization of a

  polysaccharide having a helicoidal rod structure.

  Several viscous polysaccharides such as xanthan, lentinan, schizophyllan, scleroglucan or curdlane have been found to possess helicoidal structures with two or three layers (T Norisuye, et al J Polymer Science, Polymer Physics Ed 18, 547-558 (1980)). ): EDT Atkins and KD Parker, J Polymer Science Part C 28, 69-81 (1969): TL Bluhm and A Sarko, Can J.

  Chem 55, 293-299 (1977): R H Marchessault, and Coil Can J Chem 55, 300-

  303 (1977): E Morris; A C Symposium Series, No. 45, 81 (1977): E. Morris, et al .; J Mol, Biol 110, 1 (1977)) The potentials of these polysaccharides have been investigated, some have been developed as thickeners for the food industry on the basis of their viscosities and it has been found that others have potent host-mediated antitumor activities But in some cases, extremely high viscosities

  their solutions have made their use difficult.

  In order to properly reduce their viscosities, we invented a

  ultrasonic method for the depolymerization of polysaccharides (Japanese patent

  (57335/1977) Our research on the mode of ultrasonic depolymerization has confirmed that it was mainly due to the separations of the main chain of the polysaccharide and that neither the side chain nor the carbon in the glucose residue did not intersect

  during the sonic depolymerization Thus, the degraded polysaccharide results

  both consists of the same periodic unit and it also has the same

  helical structure than that of the original polysaccharide.

  Recently, it has been found that the method of ultraviolet depolymerization

  sounds did not occur for industrial depolymerization of a large volume

  polysaccharides due to its low efficiency The depolymer-

  Ultrasonic noise also implies high noise and erosion

  of the vibration rod of the ultrasonic oscillator.

  The present invention stems from the discovery that treating a polysaccharide solution at a high shear rate also depolymerizes the polysaccharide in a manner similar to that of ultrasonic treatment; that is to say that only the main chain of the polysaccharide,

  the exclusion of any other glucosidic linkage and no carbon

  carbon in the glucose residue, cuts off during the treatment of

  depolymerization performed under these conditions.

  The helicoidal structure polysaccharide is known to disperse

  in unique chains under specific conditions; for example, beta 11,3-

  D glucan disperses in single chain in an alkaline solution or dimethyl sulfoxide When the dimethyl sulfoxide solution is diluted with water or the neutralized alkaline solution with acid, one does not

  not find the helical structure of the polysaccharide but, by association

  At random, a large aggregate is formed. The present invention is only

  useful for a polysaccharide solution having a helical structure

  and not for one with a single chain structure or a structure

aggregate.

  This method has confirmed its ability to overcome the

  previous examples such as low efficiency, high noise level, or erosion

  of the vibration stem of the ultrasonic oscillator, which had been encountered

  in the ultrasonic depolymerization method.

  Acid hydrolysis and the enzymatic degradation of a poly-

  Saccharide Acidic hydrolysis also cuts off all the glycosidic bonds of the polysaccharide while enzymatic degradation causes hydrolysis

  a specific glucosidic bond.

  But their depolymerization modes are quite different from those of the ultrasonic method and the present method They release mono- or oligosaccharides with very low molecular weight and they do not lead

  quantitatively to a degraded polysaccharide which has the same

  chemical and conformation levels than those of the original polysaccharide.

  An object of the present invention is to depolymerize a polysaccharide

  wrinkle having a helicoidal structure in sticks by forcing its solution

  to flow with a high shear rate.

  Another object of the present invention is to provide a polysaccharide

  charide degxradâ particular which consists of the same periodic unit and which

  has the same elicoidal structure as the starting polysaccharide.

  The degraded polysaccharide has an extremely lower viscosity

  compared to that of the starting polysaccharide, and the polysaccharide

  still serve the physical and chemical characteristics such as

  anti-tumor of the original polysaccharide except for molecular weight and viscosity Reducing the viscosity of the solution

  is useful for its industrial use For example, it makes the adminis-

  treatment of the easy polysaccharide in the case of its clinical use as an anticancer drug, or a thixotropic solution of the starting polysaccharide is transformed into Newtonian fluid, improving the fluidity of a food

containing the polysaccharide.

  The depolymerization according to the present invention is carried out by forcing a solution of the polysaccharide to pass through a capillary with a high shear rate, preferably greater than 1 × 10 sec. Examples 1 of the polysaccharides used in the present method are xanthan gum

and beta-1,3-D glucans.

  It is found that the depolymerization efficiency of this method

  is increased when the concentration of the polysaccharide solution

  charide increases, especially when it is greater than 0.1% by weight. It has also been found that the addition of a solvent (solvent B) to the solution

  polysaccharide increases the efficiency of the depolymerization according to the present invention.

  the method when solvent B is miscible with the solvent (solvent A) of the

  polysaccharide solution and does not dissolve the polysaccharide.

  The depolymerization of the polysaccharide is carried out by forcing a solution

  polysaccharide to pass through a capillary such as jet, slot,

  or ceramic products or porous sintered plates, using a small force

  trice producing high pressure.

  The rate of depolymerization depends only on the value of the shear rate applied, which results from the driving force, the pressure, the diameter and the length of the capillary used and the viscosity of the

  While the solution is being passed through a capillary

  under certain conditions, the molecular weight of the polysaccharide decreases

  progressively, approaching a minimum value, from which no

  more de depolymerization The minimum molecular weight also depends on the value of the applied shear rate; a higher shear rate

  high gives a lower molecular weight.

  Thus, the value of the shear rate applied is a dominant factor.

  This method does not produce any depolymerisation

  at a shear rate too low. Generally, a rate of

  sanding at least greater than 1 x 104 sec 1 is necessary for this

depolymerization method.

  In order to obtain such a high shear rate, the pressure applied

  the polysaccharide solution and the cross-sectional area of the capillary are 10 -800 105 Pa and 1 X 10 100 mm 2 respectively.

these values are not limited.

  The present invention allows the following findings

  1 an increase in the concentration of the polysaccharide solution

  believes the efficiency of depolymerization.

  2 the addition of a solvent (solvent B), which is miscible with the solvent

  (Solvent A) of the polysaccharide solution and does not dissolve the polysaccharide.

  wrinkle, polysaccharide solution also increases the efficiency of depolymerization. The effect of increasing the concentration of the polysaccharide solution appears significantly when it is greater than 0.1% by weight. Although it is desirable that the concentration be as high as possible, part of the polysaccharide It tends to remain undissolved at too high a concentration because of its low solubility. Thus, in practice, the concentration is preferably 0.1% by weight.

  Solvent B is exemplified by acetone, methanol, ethanol, isobutanol

  or n-propanol, tetrahydrofuran etc. when the solvent A is water in

  in most cases water is useful as solvent A, but for a poly-

  water-insoluble saccharide such as an N-alkylol amide derivative of the polysaccharide

  wrinkle, which still has a helicoidal structure similar to polysaccharide

  charides of origin, acetone or benzene is used as the solvent A and the water as the solvent B. Although the depolymerization efficiency increases as the amount of the added solvent B increases, this amount must be limited by such

  so that no insoluble polysaccharide precipitate forms.

  The temperature has no significant influence on the result of the present depolymerization method. However, the depolymerization is generally carried out at a temperature below 1000 C.

  In order to depolymerize the polysaccharide to a certain molecular weight

  the solution is forced through a capillary repeatedly until

  that its molecular weight reaches the desired value.

  Particles suspended in the polysaccharide solution

  often truncate the capillary, leading to the stop of the operation Thus,

  the solution is preferably filtered before passing through the capillary.

  Since a solution of the polysaccharide is viscous and adhesive, a large quantity of the solution remains in the containers or other materials used, after it has been evacuated.

  the solution on the internal surfaces of the containers or equipment, it is desirable

  The moderate stirring also prevents the retention of a portion of the solution adhering to the walls of the equipment,

  leads to uniform depolymerization of the polysaccharide.

Example 1

  Schizophyllane having a molecular weight of 5.6 X 10 was dissolved in water to prepare a 0.2% by weight solution. The solution was forced to pass through a nozzle of 0.16 mm radius. actuating with the aid of a piston pump plunger Onajustele flow the solution to 0.23 cm 3 / sec, 0.90 cm 3 / sec, 14.5 cm 3 / sec and 35.4 cm 3 / sec by control of the pump speed The shear rate calculated for each flow rate from the following formula 4 -I 5 -i is respectively 7.1 × 10 sec for 0.23 cm 3 / sec flow rate, 2.8 × 10 sec, for 0.90 cm 3 / sec of flow, 4.5 X 106 sec 1 for 14.5 cm 3 / sec of flow and 1.1

  1 X 10 sec-1 for 35.4 cm T / sec of flow.

  Shear Rate = 4 X Flow IX (capillary radius Figure 1 shows the relationship between the retention time of the solution in the nozzle and the molecular weight of the polysaccharide The starting schizophyllane and all the depolymerized schizophyllans

  are methylated by the Hakomori method and then hydrolyzed with formic acid

  and then trifluoroacetic acid The hydrolyzate is acetylated with anhydrous acetic acid in pyridine The sugar components in the product are analyzed by gas-liquid chromatography and it follows that

  contains 1,5-di-O-acetyl-2,3,4,6-tetra-O-methyl-D-glucitol, 1,3,5tri-O-

  acetyl-2,4,6-tri-O-methyl glucitol and 1,3,5,6-tetra-O-acetyl-2,4-di-

  D-glucitol in a molar ratio of 1: 2: 1.

  The starting schizophyllan and all the depolymerized schizophyllans

  are oxidized with 0.01 N sodium meta-periodate and the amounts of

  Sodium periodate consumed and formic acid formed are determined by iodometry followed by titration with a sodium hydroxide solution. A consumption of 0.48 0.55 mole of sodium meta-periodate is observed.

  formation of 6-2 μl of 0.27 moles of formic acid per mole of

in schizophyllan.

  Schizophyllan and all depolymerized schizophyllans are degraded

  dice with exo-beta-1,3-D-glucanase It is confirmed that the degraded product con-

  holds glucose and gentiobiose in a molar ratio of 2: 1.

  The molecular weights of the starting schizophyllan and all schizophyllans

  phyllanes depolymerized in water as well as in dimethyl sulfoxide are

  determined by the ultracentrifugation method Each molecular weight ratio

  in water to that in dimethyl sulfoxide is between 2.8 and 3.3.

  These results indicate that each depolymerized polysaccharide has the same chemical and conformational structures as those of the polysaccharide.

departure.

Example 2

  Scleroglucan having a molecular weight of 5 X 10 6 and xanthan gum having a molecular weight of 1.4 X 10 is dissolved in water.

  to prepare with each an aqueous solution at 0.5% by weight.

  A pressure of 200 105 Pa is applied to each solution and it is passed through a nozzle of 0.1 mm radius and 5 cm length The flow rates are respectively 1.4 cm 3 / sec for scleroglucan and 7.4 x 101 cm 3 / sec for xanthan gum. Thus, the shear rate calculated from the following formula is 1.8 X 106 sec -1 for scleroglucan

252 1,569

-1

  and 9.4 X 105 sec 1 for xanthan gum.

  Shear rate 4 X flow H X (capillary radius) 3 Each solution is passed through the nozzle 10 times under the conditions above. The depolymerized scleroglucan has a molecular weight

6

  of 8 X 10 and the depolymerized xanthan gum of 1.05 X 10 respectively.

  The starting polysaccharides and the resulting polysaccharides are methylated and then acetylated as described in Example 1, then the constituents of the products are analyzed by gas-liquid chromatography. The analyzes show that each depolymerized polysaccharide has substantially the same primary structure as

  that of the corresponding starting polysaccharide. The ratios of the molecular weights

  in the water to those in dimethyl sulfoxide of the starting scleroglucans and depolymerized are close to three, which shows the similarity between the conformational structures of the two scleroglucans The intrinsic viscosities

  of the starting xanthan gum and the depolymerized gum are respectively

  12000 dl / g and 1070 dl / g The relationship between the intrinsic viscosity and the molecular weight of each of the depolymerized xanthan gums and

  departure is in agreement with the relationship determined by Holzwarth and Coll (G.

  Holzwarth; Carbohydrate Research 66, 173-186 (1978), which indicates that

  two xanthan gums have similar helicoidal structures.

Example 3

  Schizophyllane having a molecular weight of 2 × 10 6 was dissolved in water, in a mixture of 20% by weight of acetone and 80% by weight of water, and in a mixture of 20% by weight of ethanol and 80% by weight of water, in each case at a concentration of 0.8% by weight Each solution was forced to pass through a sintered plate having a thickness of 1 cm and a mean pore size of 50 microns with a pressure of 400 105 Pa I 1 is evident from the following formula that the shear rate

6 -1

  for each solution is greater than 2.5 X 10 sec.

  Shear rate = (pressure) X (capillary diameter) 2 X (viscosity of the solution) X (capillary length) The viscosity of each solution is less than 38 cp. After 5 passes of each solution through the sintered plate, the

  polysaccharide has the following molecular weight.

  Molecular weight Aqueous solution of ethanol 5.3 X 10 Aqueous solution of acetone 6.0 X 10 Water 7.8 X 105

1 Example 4

  Scleroglucan having a molecular weight of 5.2 X 10 6 was dissolved in water to prepare an aqueous solution of 0.1% by weight, 0.45% by weight and 0.90% by weight. solution at a pressure of 170 Pa to pass through a nozzle of 0.16 mm radius After 20 passes, the polysaccharide in each solution has the following molecular weight. Concentration of the solution Molecular weight 0.1% by weight 5.8 X 10 0.45% by weight 4.2 X 10 0.90% by weight 2.8 X 10

Example 5

  An aqueous solution of 1.0% by weight of the schizophyllane used is filtered off.

  in Example 1 using a ceramic filter having 0.1 mm pores.

  A pressure of 50 105 Pa is applied to a container filled with the filtrate to force the filtrate to pass through a 0.515 mm nozzle which is sent to the vessel. The filtrate is stirred in the vessel at a Reynolds number = 120. same operations for 8 hours The molecular weight of the schizophyllane is 3.7 X 106 for the treatment. Once the solution is removed from the container, 100 ml of the solution remains in the container which adheres to

its internal surface.

  The same solution of schizophyllan was forced through the same nozzle but without filtration on the ceramic filter or agitation during its treatment. The operations were stopped several times because of the obstruction of the nozzle by suspended particles in the solution Once the solution is removed from the container, 2500 ml of the

  solution in the bottom of the container, flowing along the wall.

Claims (10)

  Process for the depolymerization of a polysaccharide having a helicoidal rod structure, characterized in that it comprises a step of forcing a solution of the polysaccharide in a solvent (solvent A) through a capillary with a high shear rate, to produce a lower molecular weight degraded polysaccharide, which has the same periodic unit and helical structure as those of the original polysaccharide.   Process according to Claim 1, characterized in that the poly-   saccharide is a beta-1,3-D glucan.   3. Process according to claim 1, characterized in that the poly- saccharide is schizophyllan.   Process according to claim 1, characterized in that the poly- saccharide is scleroglucan.   Process according to claim 1, characterized in that the poly-   saccharide is xanthan gum.   Process according to one of Claims 1 to 5, characterized   in that the polysaccharide solution is treated with a shear rate 4 -1 greater than I X 10 sec   Method according to one of Claims 1 to 6, characterized   in that the concentration of the polysaccharide solution is 0.1 10% in weight.   Process according to Claim 1, characterized in that the solvent A is water.   Process according to any one of the preceding claims,   characterized in that a solvent (solvent B) other than the solvent A, which is a poor solvent or non-solvent of the polysaccharide and which is also   miscible with the solvent A, is added to the polysaccharide solution.   Process according to any one of the preceding claims,   M O characterized in that the polysaccharide solution is filtered before its   treatment at a high shear rate.   Method according to any one of the preceding claims,   characterized in that the polysaccharide solution is moderately agitated   during treatment at a high shear rate.