Process for preparing (1→6)-α-D-glucan

Abstract

A process for preparing (1.fwdarw.6)--D-glucan. A large amount of (1.fwdarw.6)--D-glucan can be prepared from banana by using this process. The chemical structure of (1.fwdarw.6)--D-glucan is shown as Scheme 1. The yield of (1.fwdarw.6)--D-glucan is 3-16 g/kg (with a purity of 85%-95%). This process provides a feasible technique for extensive utilization of banana, and can improve the additional value of banana products. This process is helpful for the sustainable development of banana processing industry. ##STR00001##

Claims

1. A process for preparing (1.fwdarw.6)--D-glucan, comprising the following steps: extracting banana pulp with water to give a supernatant; separating, collecting and concentrating the supernatant, adding ethanol into the concentrated supernatant to precipitate crude banana polysaccharides, and collecting the crude banana polysaccharides; purifying the crude banana polysaccharides with anion exchange resin, and eluting with water or phosphate solution to obtain a fraction eluted with water or a fraction eluted with phosphate solution; concentrating and drying the fraction eluted with water to obtain the (1.fwdarw.6)--D-glucan, or, concentrating, dialyzing and drying the fraction eluted with phosphate solution to obtain the (1.fwdarw.6)--D-glucan.

2. The process according to claim 1, comprising purifying the crude banana polysaccharides over an anion exchange column and eluting with water to obtain a fraction eluted with water, and concentrating and drying the fraction eluted with water to obtain the (1.fwdarw.6)--D-glucan.

3. The process according to claim 1, comprising purifying the crude banana polysaccharides over an anion exchange column and eluting with phosphate solution of pH 7.0 to obtain a fraction eluted with phosphate solution, and concentrating, dialyzing and drying the fraction eluted with phosphate solution to obtain the (1.fwdarw.6)--D-glucan.

4. The process according to claim 1, wherein extracting banana pulp with water comprises: adding the banana pulp into water wherein a weight of the water is 1-30 times that of the banana pulp, and performing extraction at 25-100 C. for 1-120 hours.

5. The process according to claim 1, wherein separating the supernatant is by centrifugation or filtration.

6. The process according to claim 1, wherein in the step of adding ethanol into the concentrated supernatant, a final volume fraction of the ethanol is 20%-90%.

7. The process according to claim 1, wherein the banana pulp is fresh banana pulp or dried banana pulp.

8. A method of using banana pulp in preparing (1.fwdarw.6)--D-glucan, comprising the steps: extracting banana pulp with water to give a supernatant; separating, collecting and concentrating the supernatant, adding ethanol into the concentrated supernatant to precipitate crude banana polysaccharides, and collecting the crude banana polysaccharides; purifying the crude banana polysaccharides with anion exchange resin, and eluting with water or phosphate solution to obtain a fraction eluted with water or a fraction eluted with phosphate solution; concentrating and drying the fraction eluted with water to obtain the (1.fwdarw.6)--D-glucan, or, concentrating, dialyzing and drying the fraction eluted with phosphate solution to obtain the (1.fwdarw.6)--D-glucan.

9. The method according to claim 8, comprising purifying the crude banana polysaccharides over an anion exchange column and eluting with water to obtain a fraction eluted with water, and concentrating and drying the fraction eluted with water to obtain the (1.fwdarw.6)--D-glucan.

10. The method according to claim 8, comprising purifying the crude banana polysaccharides over an anion exchange column and eluting with phosphate solution of pH 7.0 to obtain a fraction eluted with phosphate solution, and concentrating, dialyzing and drying the fraction eluted with phosphate solution to obtain the (1.fwdarw.6)--D-glucan.

Description

EMBODIMENTS OF THE INVENTION

(1) The following embodiments are used for further describing this invention rather than limiting the invention.

Embodiment 1: Preparation and Structure Identification of (16)--D-glucan

(2) 1. Preparation of (1.fwdarw.6)--D-glucan

(3) 1) Material: Fresh bananas are collected and the pulps are obtained by removing the peels.

(4) 2) Extraction: Water is added to the banana pulps wherein a weight of the water is 10 times of that of the banana pulps. The extraction is conducted at 60 C. for 1 hour. After centrifugation, the supernatants are collected.

(5) 3) Solvent precipitation: The supernatants are concentrated and ethanol is added to a final concentration of 90% (volume/volume). After incubation at 4 C. for 12 hours, the pellets are collected by centrifugation. The pellets are crude banana polysaccharides.

(6) 4) Column purification: The crude banana polysaccharides are purified over a DEAE Sepharose Fast Flow anion exchange column which is eluted with water and subsequently with 1M NaCl solution. The fraction eluted with water is collected, concentrated and dried and thereby a compound 1 ((1.fwdarw.6)--D-glucan) is obtained. The yield of (1.fwdarw.6)--D-glucan prepared by this protocol is 8-12 g/kg. The purity is 85%-95%.

(7) 2. Structure Identification of the Compound 1 ((1.fwdarw.6)--D-glucan)

(8) Compound 1 ((1.fwdarw.6)--D-glucan) is water soluble. Through analyses by .sup.1H NMR (500 MHz, D.sub.2O) and .sup.13C NMR (125 MHz, D.sub.2O), the chemical shifts are assigned and listed in Table 1.

(9) TABLE-US-00001 TABLE 1 The .sup.1H and .sup.13C chemical shifts of (1.fwdarw.6)--D-glucan Position .sup.1H .sup.13C 1 5.01, d, J = 2.4 Hz 97.7 2 3.59, d, J = 9.5 Hz 71.4 3 3.74, d, J = 9.5 Hz 73.4 4 3.56, d, J = 9.5 Hz 69.8 5 3.95, d, J = 7.5 Hz 70.0 6 4.03, d, J = 7.5 Hz; 65.3 3.81, d, J = 12.5 Hz

(10) According to the NMR results, the compound 1 is identified as (1.fwdarw.6)--D-glucan. The structure is shown in Scheme 1.

(11) ##STR00003##

Embodiment 2

(12) 1) Material: Fresh bananas are collected and the pulps are obtained by removing the peels.

(13) 2) Extraction: Water is added to the banana pulps wherein a weight of the water is the same with that of the banana pulps. The extraction is conducted at 25 C. (Ambient temperature) for 120 hours. After filtration, the supernatants are collected.

(14) 3) Solvent precipitation: The supernatants are concentrated and ethanol is added to a final concentration of 20% (volume/volume). After incubation at 4 C. for 12 hours, the pellets are collected by centrifugation. The pellets are crude banana polysaccharides.

(15) 4) Column purification: The crude banana polysaccharides are purified over a DEAE Sepharose Fast Flow anion exchange column which is eluted with water and subsequently with 1M NaCl solution. The fraction eluted with water is collected, concentrated and dried and thereby (1.fwdarw.6)--D-glucan is obtained (structure identification shows the same result with embodiment 1).

(16) The yield of (1.fwdarw.6)--D-glucan prepared by this protocol is 3-8 g/kg. The purity is 85%-95%.

Embodiment 3

(17) 1) Material: Fresh bananas are collected and the pulps are obtained by removing the peels.

(18) 2) Extraction: Water is added to the banana pulps wherein a weight of the water is 30 times of that of the banana pulps. The extraction is conducted at 100 C. for 5 hours. After filtration, the supernatants are collected.

(19) 3) Solvent precipitation: The supernatants are concentrated and ethanol is added to a final concentration of 60% (volume/volume). After incubation at 4 C. for 12 hours, the pellets are collected by centrifugation. The pellets are crude banana polysaccharides.

(20) 4) Column purification: The crude banana polysaccharides are purified over a DEAE Sepharose Fast Flow anion exchange column which is eluted with water and subsequently with 1M NaCl solution. The fraction eluted with water is collected, concentrated and dried and thereby (1.fwdarw.6)--D-glucan is obtained (structure identification shows the same result with embodiment 1).

(21) The yield of (1.fwdarw.6)--D-glucan prepared by this protocol is 12-16 g/kg. The purity is 85%-95%.

Embodiment 4

(22) 1) Material: Fresh bananas are collected and the pulps are obtained by removing the peels.

(23) 2) Extraction: Water is added to the banana pulps wherein a weight of the water is 30 times of that of the banana pulps. The extraction is conducted at 60 C. for 5 hours. After filtration, the supernatants are collected.

(24) 3) Solvent precipitation: The supernatants are concentrated and ethanol is added to a final concentration of 80% (volume/volume). After incubation at 4 C. for 12 hours, the pellets are collected by centrifugation. The pellets are crude banana polysaccharides.

(25) 4) Column purification: The crude banana polysaccharides are purified over a DEAE cellulose anion exchange column which is eluted with phosphate solution (pH 7.0) and subsequently with phosphate solution (pH 7.0) containing 1M of NaCl. The fraction eluted with phosphate solution (pH 7.0) is collected, concentrated, dialysed and dried and thereby (1.fwdarw.6)--D-glucan is obtained (structure identification shows the same result with embodiment 1).

(26) The yield of (1.fwdarw.6)--D-glucan prepared by this protocol is 9-13 g/kg. The purity is 85%-95%.