CS202155B1 - Process for the insulation of l-arabinose from hydrolyzates of bark of leafy trees - Google Patents

Description

SUMMARY OF THE INVENTION The present invention provides a process for the isolation of L-arabinose from the foliage hydrolysates of p-nitrophenyl-L-arabinozylamine.

Deciduous woody trunks contain about 17% hemicellulose (A. Kramár, A. Ebringerová; Paper and cellulose 31. V38 (1976)), of which aldopentoses are released under mild acid hydrolysis conditions. Hydrolysis of beechwood trellis, depending on the concentration of sulfuric acid (1-2%), temperature (100-120 ° C) and hydrolysis time (2-6 hours) a, gives a mixture of L-arabinose and D-xylose in different weight ratios ( 2.6: 0.2 to 3.0: 13.1) with a total aldopentosis yield of 2.8 - 16.1% calculated per time kdru (A. Kramář. P. Rendoá; Czech author's certificate No. 181485). The separation of aldoses from a mixture of L-arabinose and D-xyclose directly by crystallization is problematic, since in each case and only a small fraction of these aldoses are obtained in crystalline form, also only in the mixture. The proposed method allows for relatively simple procedures to isolate L-arabinose from a mixture of L-arabinose and D-xylose.

The principle of the invention is that in a slightly acidic methanolic solution, arabinose and xylose with p-nitroaniline convert to N-p-nitrophenylglycosylamines, from which N-p-nitrophenylarabinozylamine crystallizes directly from the reaction solution. Hydrolysis of crystalline N-p-nitrophenylarabinozylamine yields high purity arabinose.

The advantage of the proposed method of isolating L-arabinose from hydrolysates of deciduous woody species is that

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- makes it possible to obtain arabinose from a mixture of arabinose and high purity xylosis,

- the procedure can also be used for cleaning D- resp. L-arabinose, respectively. isolation of arabinose from the mother crystallization solutions from which a saline amount can no longer be obtained in the crystalline state,

is low on technological equipment, and

- chemicals, since the p-nitroaniline used is almost quantitatively regenerated and is suitable, without special purification, for the more complete arabinose isolation cycles.

Example 1

Isolation of L-arabinose from beech kernel hydrolyzates

Beech brush (1 kg, particle size up to 1.5 mm, 93% dry matter) was suspended in 2% sulfuric acid (8 L) and the mixture was held at 100 ° C for 4 hours. The solution is filtered, the filtrate is neutralized with a saturated aqueous solution of calcium hydroxide, treated with activated carbon and deionized with ion exchangers (Wofatit KPS in H ⁺ -cycle, Wofatit SBW in an acetate cycle). The non-ionized solution is concentrated to give neutral carbohydrates (59 g - arabinose, xyloza and a small amount of galactose, mannose, glucose and rhamnose) which are dissolved in drinking water (1 liter) and after the addition of baker's yeast (10 g) ferment until complete removal of D-galactose. The solution is filtered, concentrated to dryness to give a mixture of L-arabinose and D-xylose (52 g) in a ratio of about 1 ί 1. The distillation residue (52 g) is dissolved in methanol (250 ml), p-nitroaniline is added. (40 g), acetic acid (10 mL) and the mixture was heated at 65 ° C for 3 hours and then allowed to stand at room temperature for 20 hours. Crystalline Np-nitrophenyl-L-arabinozylamine (35 g) ea was filtered off, washed with methanol and then suspended in water (175 ml) and after addition of acetic acid (17 ml) the mixture was heated at 90 ° C for 4 hours. The precipitated p-nitroaniline (18 g) was filtered off and the filtrate was concentrated to dryness. The distillation residue was dissolved in water (100 mL), the solution was treated with charcoal and then concentrated to dryness to give L-arabinose (18 g) without D-xylose trace.

Example 2

Isolation of D-arabinose from a mixture of D-arabinose and D-xyloza

A mixture of eldopentoses (4.5 g), p-nitroaniline (4.2 g), methanol (20 ml) and acetic acid (1 ml) was heated at 65 ° C for 3 hours. The reaction mixture was allowed to stand at room temperature for 20 hours and then crystalline N-p-nitrophenyl-D-arabinozylamine was filtered off and washed with methanol (results are shown in Table 1). D-arabinose is released from N-p-nitrophenyl-D-arabinozylamine as shown in Example 1.

The purity of the aldopentoses as well as the composition of the reaction mixtures are monitored by chromatography on Whatman No 1 paper, eluting with n-butanol-ethanol-water (5: 1: 4), the arabinose (1.00) mobility being xylose 1, 14, galactose 0.70, Np-nitrophenylarabinozylamine 2.97, Np-nitrophenylxylozylamine 3.22 and 3.59, Np-nitrophenylgalactosylamine 2.84 and p-nitroaniline 4.23.

The invention is applicable to the production of commercially interesting L-arabinose from bark waste, which represents about 10% of the wood used.

202 135 Table 1

Isolation of D-arabinose from a mixture of D-arabinose and D-xylose as N-p-nitrophenyl-D-arabinozylamine

D-arabinose a (G) D-xylose Crystalline N-p-nitrophenyl- D-arabinozylamín kg) Conversion of D-arabinose to N-glycoside (G) 4.5 - 6.9 85.2 3.0 1.5 4.35 80.4 2.25 2.25 3.0 74.7 1.5 3.0 1.65 61.1

OBJECT OF THE INVENTION

Claims (1)

Process for the aialation of L-arabinose from hydrolysates of crystalline woody species, characterized in that in a slightly acidic methanolic solution arabinose and xyloza with p-nitroaniline are converted to Np-nitrophenylglycosylamines, high purity ^