JPH064679B2 - Powdered silk fibroin peptide and method for producing the same - Google Patents

Description

TECHNICAL FIELD The present invention relates to a high-purity powdery silk fibroin peptide and a method for producing the same, and in particular, a powdery silk fibroin peptide that is easily soluble in cold water and is suitable as a cosmetic base. And its manufacturing method.

(Prior Art) Since silk fibroin powder has properties such as its moderate hygroscopicity and moisturizing property, excellent affinity and smoothness to the skin, and further a protective action to the skin, it has been mainly used in the past. It has been used for applications such as cosmetic bases.

Conventionally, as a silk fibroin powder, Japanese Patent Publication No. 40-249
No. 20, JP-B No. 26-4947 and JP-B No. 58-38449 disclose suitable fibrous silk fibroin powder or silk fibroin obtained by crushing silk thread as it is or by embrittlement by chemical treatment. Granulated silk fibroin powder obtained by crushing gel silk fibroin produced by dissolving and dialysis the obtained colloidal solution in various concentrated neutral salts, and silk fibroin as an appropriate inorganic neutral salt or alkaline aqueous solution. From the colloidal solution obtained by dissolving in water and dialysis or not, adding coagulable salt, sucking in air,
There is disclosed finely powdered silk fibroin obtained by coagulating and depositing silk fibroin by isoelectric point coagulation, ultrasonic treatment, stirring at a high shear deformation rate, dehydration, drying and pulverization.

However, the silk fibroin powder described in JP-B-40-24920 has various drawbacks when used as a cosmetic base because it is fibrous and has large particles.
Further, the silk fibroin powder described in JP-B No. 26-4947 is unsuitable as a cosmetic base because water-soluble and water-insoluble silk fibroin are mixed due to powder mist drying and reaggregation easily occurs.

In any case, since the silk fibroin powder obtained by these methods is insoluble in water to most of it insoluble in water, it is limited to makeup bases for makeup because of its cosmetic use. It is unsuitable as a base material.

As for the aqueous cosmetic base made from silk fiber, a powder mainly composed of mixed amino acids produced by decomposition of silk fiber by boiling and decomposition of silk fiber in a strong acid aqueous solution with hydrochloric acid, sulfuric acid, phosphoric acid, etc. As described in JP-B No. 42-17030, a solution obtained by treating silk fibroin with high-concentration phosphoric acid is mixed with a coagulant made of a specific organic solvent such as acetone to form a partially decomposed product. A method is known in which a precipitate is precipitated, this is dispersed again in water, a proteolytic enzyme is allowed to act thereon, and then the precipitate is precipitated using the above coagulant.

Of these methods, the former is not particularly useful as a cosmetic base because it uses a mixed amino acid as a main component. Also, in the latter case, since the reaction is essentially a solid-liquid reaction, the molecular weight distribution must be widened, and if the average molecular weight is lowered, the amount of amino acids produced will inevitably increase and precipitation with a coagulant will be difficult. Therefore, there are problems in terms of quality and cost, and operation is complicated.

On the other hand, in JP-A-56-40695, an aqueous solution of copper-ethylenediamine, an aqueous solution of copper hydroxide-alkali-glycerin, an aqueous solution of lithium bromide, an aqueous solution of calcium or magnesium or zinc hydrochloride or an aqueous solution of nitrate or thiocyanate, thiocyanate. Silk fibroin obtained by hydrolyzing 0.5 to 20% by weight of silk fibroin aqueous solution obtained by dissolving scouring silk raw material in at least one solvent selected from the group consisting of sodium acid aqueous solution and dialysis The average degree of polymerization n obtained by pulverizing the aqueous peptide solution by a spray drying method is 2 to 45, and 10
As an average particle size of ˜40 μ and a bulk density ρ (g / cm ³ ) of e ^{−0.095n-1.77} + 0.04 ≦ ρ ≦ e ^{−0.095n-1.77} + ^0.06 A method for producing an amorphous, water-soluble powdery fibroin peptide has been proposed.

In the case of this method, since the solvent is mild, it does not damage the protein structure of silk fibroin, which is useful as a base material for cosmetics. Is carried out using a multi-layered membrane structure or a hollow fiber focusing structure satisfying the above condition, and since the hydrolysis is uniformly carried out by a liquid-liquid reaction, the obtained silk fibroin peptide has a narrow molecular weight distribution, Since the average molecular weight is easy to adjust and the drying is instantaneously performed by a spray drying method, the silk fibroin peptide is useful as a base for aqueous cosmetics, and has relatively high solubility and dissolution rate in water. can get.

However, this method is characterized in that it is dried by a spray dry method, but on the other hand, it has a problem unique to the spray dry method.

That is, in the case of this method, since the dried product is extremely porous, the bulk density is abnormally small. For example, the average molecular weight of the most useful peptide as a base for an aqueous cosmetic composition is 1,000 to 3,000, but in this case, the average degree of polymerization n = 11 to 34. When this is applied to the bulk density of the method, 0.0467 ≤ ρ ≤ 0.120, ρ ≤ 0.201 even for the highest bulk density of n = 2, and ρ ≤ 0.188 for n = 3. That is, when n = 11 to 34, the powder volume is 8.3 to 21.4 / Kg, and when n = 3, 5.3 /
Kg is 5.0 / Kg even when n = 2, and the volume per weight is remarkably high. Therefore, it reduces the production efficiency and operability of the powder, and is not only costly in terms of storage and transportation, but it is also a light powder when actually used, so it is scattered in the air and there is no loss. There are many problems such as polluting the environment.

Also in this method, if the spray-drying conditions are selected, a bulk density of 0.2 g / cm ³ or more can be obtained even if the average degree of polymerization is about 4, but in that case, the dissolution rate is extremely reduced, which is not practical.

(Problems to be Solved by the Invention) The present inventors have completed the present invention as a result of earnest research on a water-soluble peptide having the characteristics of silk fibroin and having an appropriately high bulk density. An object of the present invention is to provide a powdery silk fibroin peptide useful in cosmetics and the like, which has a large solubility in water and a large dissolution rate, retains preferable properties of silk fibroin, has good hygroscopicity, good moisture retention, and has a suitable bulk density. To provide. Another object is to provide a method for industrially easily and inexpensively producing such powdery silk fibroin peptide.

(Means for Solving the Problems) The above-mentioned object is powdery silk having an average degree of polymerization of ³ to 600 and a bulk density of 0.2 to 0.7 g / cm ^{3 with} an average particle size of 10 to 40 μm. A fibroin peptide, at least 50% by weight of which is a substantially amorphous powdery silk fibroin peptide having an α structure easily soluble in cold water, and silk fibroin obtained by dissolving silk fiber in an aqueous medium. The silk fibroin in the solution may be hydrolyzed or may be freeze-dried after the silk fibroin solution is adjusted to have a silk fibroin concentration of 2 to 40% by weight and a pH of 4.5 to 7.5 without hydrolysis. It is achieved by a method for producing a powdered silk fibroin peptide, which is characterized in that The average degree of polymerization of the powdery silk fibroin peptide of the present invention is 3 to 600, preferably 5 to 100, and particularly preferably 10 to 40. When the average degree of polymerization is less than 3, the amino acid content increases, and when used as a raw material for cosmetics, for example, the moisturizing and conditioning effects on the skin peculiar to silk fibroin are impaired,
Furthermore, when used as an aqueous cosmetic base, it lacks film-forming properties. On the other hand, the average degree of polymerization is 600 (average molecular weight ≈ 50,
000), the solubility in water remarkably decreases and becomes substantially the same as the silk fibroin powder described in JP-B-58-38449, and the freeze-drying method is economical. Since it is inferior to this, the significance of implementation is small.

The powdered silk fibroin peptide of the present invention has 0.2 to 0.7 g.
It has a bulk density of / cm ³ . A bulk density of less than 0.2 g / cm ³ causes various troubles in production efficiency, operability, storage, transportation, and environmental measures at the production site. In addition, in the case of freeze-drying, in order to produce powdery silk fibroin peptide of less than 0.2 g / cm ^{3, the} concentration of silk fibroin aqueous solution to be freeze-dried needs to be 2% or less, which is not economical. A bulk density of more than 0.7 g / cm ³ can be obtained when the concentration of the silk fibroin peptide aqueous solution to be lyophilized is 40% or more, but the solubility and the dissolution rate in water are remarkably low. Not practical as a cosmetic base. In addition, this compound has less than 50% by weight of a peptide which is easily soluble in cold water (α structure).

In the same kind of aqueous solution, by spray drying and freeze drying,
It is considered that the cause of the remarkable difference in the bulk densities of the powders produced is due to the difference in the drying mechanism between the two, but the details are unknown. It is presumed that there is some cause of the microporous structure of the dried product generated by the water vaporized due to the difference in atmospheric temperature, pressure and the like.

The scouring silk raw material used in the present invention includes eyebrows, raw silk, eyebrows,
Raw silk scraps, screws, fried cotton, silk cloth scraps, burettes, etc. are used in accordance with a conventional method, if necessary, in the presence of an active agent, in warm water or in the presence of an enzyme to remove sericin and then dried.

The solvent of silk fibroin applied to the present invention is copper-ethylenediamine aqueous solution, copper hydroxide-ammonia aqueous solution (Schweiser reagent), copper hydroxide-alkali-glycerin aqueous solution (Lohe reagent), lithium bromide aqueous solution, calcium or magnesium or An aqueous solution of zinc hydrochloride or nitrate or thiocyanate, and an aqueous solution of sodium thiocyanate can be mentioned, but calcium or magnesium hydrochloride or nitrate is preferable from the viewpoint of cost and use. The concentration of these aqueous solutions varies depending on the type of solvent used, temperature, etc., but the concentration of metal salts and the like is usually 10 to 80% by weight, preferably 20 to 40% by weight. Although it dissolves even at 80% by weight or more, there is no substantial difference in the peptides produced, which is a problem in terms of economy.

The silk raw material after scouring is added to a solvent consisting of the above aqueous solution and uniformly dissolved in a device such as a kneader at a temperature of 60 to 95 ° C, preferably 70 to 85 ° C, but the liquid ratio is usually 2 to 50, preferably 3 to 30.

In order to obtain high-purity silk fibroin peptide from the obtained silk fibroin solution, dialysis is subsequently performed. For dialysis, a dialysis membrane typified by a cellophane membrane or a dialysis machine using hollow fibers is used to almost completely remove the salts and the like.
In this case, in order to narrow the molecular weight distribution of the desired silk fibroin peptide as much as possible, the ratio of the α-structure peptide was 5
In order to adjust it to 0% by weight or more, it is necessary to specify the dialysis amount and the dialysis membrane area. That is, desalting is performed using a multilayer membrane structure or a hollow fiber focusing structure that satisfies the following formula.

(Here, the priming capacity indicates the inner volume between the dialysis tube or the membrane.) When the above numerical value is less than 10, the membrane separation is not performed rapidly, so that the residence time in the dialyzer becomes longer and the resulting fibroin is obtained. In many cases, the aqueous solution has already started to rot.
In that case, the fibroin protein becomes insoluble in water (β structure) due to denaturation due to putrefaction, and it is difficult to make it soluble in cold water.

In particular, in order to carry out the present invention smoothly and economically, the above numerical value is preferably 30 or more, particularly preferably 50 or more. In order to satisfy this condition, for example, in the case of a hollow fiber bundle structure, the hollow fiber diameter must be 4 mm or less.

The dialysate obtained by the method of the present invention has a residual salt concentration of 0.
003 to 0.06% by weight, which is extremely small, especially when the diameter of the hollow fiber is about 0.2 mm, This can be achieved with a residence time in the dialyzer of several 10 minutes, and a silk fibroin peptide of extremely high quality can be obtained.

The dialysate transferred to freeze-drying has a silk fibroin concentration of 2 to
When the concentration of the peptide is adjusted to 40% by weight, preferably 3 to 30% by weight, more preferably 10 to 20% by weight, if necessary, and the average molecular weight of the peptide is several hundreds to several thousands. Prior to freeze-drying, this is hydrolyzed with an enzyme or acid or alkali.

Enzymes applicable to the present invention are obtained from usual proteolytic enzymes, for example, pronase obtained from actinomycetes, enzyme group considered to be a mixture of several proteases such as prolase obtained from papaya, and fungi such as Aspergillus niger. Proteases and proteases obtained from bacteria such as Bacillus subtilis, for example, Zuptilisin BPN
Alternatively, trypsin, chymotrypsin, papain, promelin and the like can be mentioned, and these can be used alone or in combination of two or more kinds. The amount of the enzyme used varies depending on the type of enzyme, the purity, the reaction conditions, the average degree of polymerization of the desired silk fibroin, etc., but is usually 0.01 to 10.0% by weight, and preferably 0.1% by weight based on the silk fibroin. 02-5.0
% By weight. The conditions of hydrolysis in this case differ depending on the kind and concentration of the enzyme used, but usually pH = 5 to 9, preferably 6 to 8.5, and the temperature is 20 to 70 ° C., preferably 3
It is carried out at 0 to 45 ° C. for 0.1 to 72 hours, preferably 0.5 to 12 hours.

Examples of the acid applicable to the present invention include inorganic acids such as hydrochloric acid and sulfuric acid or citric acid, organic acids such as liquor soap, malonic acid, succinic acid and maleic acid.

As the alkali applied to the present invention, sodium hydroxide,
Inorganic alkalis such as potassium hydroxide, lithium hydroxide and aqueous ammonia, and organic alkalis such as methylamine can be used, but sodium hydroxide and potassium hydroxide are preferred from the viewpoints of reactivity, economy and stability.

The condition of hydrolysis with an acid or alkali varies depending on the type of acid or alkali used, the average degree of polymerization of the desired powdery silk fibroin peptide, the degree of polymerization distribution, etc.
At a concentration of 0.03 to 3.0 N, preferably 0.3 N or less, the temperature is 20 to 110 ° C., preferably 30 to 100 ° C., and 0.5
The reaction is carried out for ~ 48 hours, preferably 1-24 hours, and then an alkali or acid is added to neutralize.

In the method of the present invention, the obtained silk fibroin peptide aqueous solution is subsequently dried by freeze-drying. Freeze-drying can be carried out by an ordinary freeze-dryer, but when the silk fibroin peptide concentration in the aqueous solution is less than 2%, the obtained dried product is almost the same as that in the spray-drying method and is extremely porous. And the bulk density was always less than 0.2 g / cm ³ . On the other hand, when the silk fibroin concentration exceeds 40%, the bulk density of the obtained dried product exceeds 0.7 g / cm ³ , and the solubility and dissolution rate in water become extremely low. For example, as a base for aqueous cosmetics. Not practical. As a result of factual analysis, the ratio of the peptide (α structure) easily soluble in cold water was less than 50% by weight. This ratio is 30%
75% by weight, and 20% concentration is virtually 100
% By weight.

In the freeze-drying treatment, for example, first, a silk fibroin peptide aqueous solution is poured into a shallow vat-shaped container to a depth of 5 to 10 m / m, and the whole is once rapidly cooled to −20 to −30 ° C. and frozen. Insert this in multiple stages on the shelf in the freeze-drying chamber, about 0.5 torr at the beginning, 0.05 torr at the end
Dry under reduced pressure. During vacuum drying, the heat of vaporization is replenished by the heater embedded in the shelf to adjust the surface temperature of the frozen product to an appropriate range.

(Effect of the invention) The obtained powdery silk fibroin peptide has a large solubility and dissolution rate in water, good film-forming ability in an aqueous solution, good hygroscopicity and moisturizing property, and has an appropriate bulk density. Therefore, it is excellent in economical efficiency and operability, and is useful as a base for cosmetics, a capsule for pharmaceuticals, a base for analysis, and the like.

Hereinafter, the present invention will be specifically described with reference to examples. The measurement and the calculation of the measurement results in the examples were carried out by the following method.

a. Peptide average degree of polymerization measurement The molar amount of amino acids when the peptide is completely hydrolyzed is determined, and this is designated as (a). The amount of terminal groups of the peptide was measured and this is designated as (b). The average degree of polymerization is calculated as (a) / (b).
To obtain (a), (1) subtract the ash content from the absolute dry solid content, and obtain this from the average molecular weight of the amino acids constituting fibroin. (2) The amount of nitrogen atoms determined by Kjeldahl nitrogen measurement is defined as the amino acid molar amount (this is substantially small because the amount of basic amino acids that compose fibroin is very small). (3) After hydrolysis with sodium hydroxide or hydrochloric acid, the produced amino acid is subjected to ninhydrin colorimetric determination. Although there are slight differences in each measurement method, they generally show good agreement. In (b), the terminal —CO ₂ H group may be measured by the formol measurement method, but the constituent amino acids of fibroin are substantially neutral amino acids, and therefore the accuracy is good.

b. Peptide bulk density measurement method Using a commercially available powder tester, powder (average particle size 10
The bulk density of the silk fibroin peptide (prepared to ˜40 μ) was measured.

c. Peptide crystallinity measurement The crystallinity was measured including the crystalline state of the powdered silk fibroin peptide by the self-recording method (by the reflection powder method) by X-ray diffraction or the photographic method.

d. Measurement of ratio of peptide (α structure) easily soluble in cold water 10 g of silk fibroin peptide prepared to 10 to 40 μm in 50 cc of cold water at 25 ° C. was dissolved by stirring for 5 minutes, and the peptide that remained without being dissolved was weighed in absolute dry ( Wg) and calculated by the following formula.

Example 1 Using silk spinning waste as a raw material for silk fibroin,
00 parts was stirred and scoured with a solution of 30 parts of Marcel soap and 3000 parts of water at 95 to 98 ° C for 3 hours to give 0.1% residual glue.
The water content was reduced to the following, washed with water, and dried with hot air at 30 ° C. Calcium chloride (CaCl ₂ .4H ₂ O) was dissolved in water to prepare an aqueous solution having the concentration shown in Table 1 and heated to 70 ° C. 20 parts of the above spinning waste was dissolved in 100 parts of this with stirring using a kneader to produce a silk fibroin solution. As shown in Table 1, in the method of the present invention, the silk waste was easily dissolved, but Comparative Example 1- (1)
When the concentration of calcium chloride was less than 10% by weight as described above, it was hardly dissolved even for a long time (24 hours or more). Next, inner diameter 200μ, film thickness 20μ, length 500
Using a hollow fiber type dialysis machine in which 2,000 mm regenerated cellulose-based hollow fibers are bundled, and both ends of which are bundled and fixed (sealed) without blocking the hollow holes, It was made to flow in at a ratio and desalted to obtain an aqueous solution of fibroin. In this case, the dialysis membrane surface area (cm ² ) / priming capacity (cm ³ ) was 200, and the residual calcium chloride in the dialysate was 0.07 to 0.033% by weight. As a result of measuring the molecular weight of fibroin in the various fibroin aqueous solutions by the peptide average degree of polymerization measurement method, Comparative Example 1-
(21), 1- (22), when the calcium chloride concentration was about 90% by weight, the molecular weight was reduced to about 40,000, and it was presumed that the protein structure was considerably damaged. The product produced by the above method had a molecular weight of 50,000 or more, and no remarkable decomposition was observed.

The various aqueous fibroin solutions obtained were concentrated or diluted to the concentrations shown in Table 1, and 0.5% by weight of silk fibroin solid content was added with biopulase conc manufactured by Nagase Seikagaku Kogyo Co., Ltd. at 20 ° C to 70 ° C. The reaction was carried out for 4 hours while raising the temperature to. The mixture was boiled for 15 minutes to complete the reaction, and then a slight white precipitate that had precipitated was removed in excess to prepare a transparent pale yellow peptide aqueous solution. The obtained silk fibroin peptide aqueous solution was rapidly cooled to −30 ° C. and frozen. This is 0.5 torr at the beginning of drying and 0.05 tor at the end.
It was dried by an ordinary freeze-drying method at about rr to produce powdered silk fibroin peptide.

Table 1 shows the average degree of polymerization, bulk density, ratio of the peptide readily soluble in cold water, and crystallinity of the obtained silk fibroin peptide.

As can be seen from the results in the above table, the freeze-dried peptide when the fibroin concentration of the method of the present invention was 2 to 40% was almost amorphous, and 50% or more had the α structure. or,
If the fibroin concentration is 2% by weight or more, the bulk density is all
The amount was 0.2 g / cm ³ or more, which was appropriate. On the other hand, as seen in the comparative example, when the fibroin concentration is less than 2%, the bulk density is 0.2 g / cm ³ or less even if the average degree of polymerization of the peptide is 3 or more, which is very porous. The peptide was obtained. Further, when the fibroin concentration exceeds 40%, the silk fibroin peptide obtained by freeze-drying has a bulk density of 0.7 g / cm ³ or more, is hard and slightly crystallized, and only a low solubility in cold water can be obtained. It was

Example 2 According to Example 1, a solution of calcium chloride was dissolved at a concentration of 40% and then dialyzed to prepare an aqueous silk fibroin solution. This was concentrated or diluted to the concentration shown in Table 2, and concentrated hydrochloric acid was added to this to make a 0.1N-HCl solution, which was heated at 95 ° C for 8 hours with stirring and then neutralized with a 5N-NaOH aqueous solution to pH = 6 It was set to .8.
This was passed through a decolorization treatment with activated carbon and then desalted with an ion exchange resin to obtain a pale yellow transparent silk fibroin peptide aqueous solution.

This was freeze-dried according to Example 1 to produce powdered silk fibroin peptide.

Table 2 shows the average degree of polymerization, bulk density, proportion of cold water easily soluble peptide (α structure) and crystallinity of the obtained silk fibroin peptide.

Also in the case of acid hydrolysis, as in Example 1, the freeze-dried peptide was almost amorphous and 50% or more was α.
It was a structure. Also, the bulk density was 0.2 to 0.7 g / cm ³ when the fibroin peptide concentration was 2 to 40%, and a powder suitable for production and use was obtained. On the other hand, when the fibroin peptide concentration exceeded 40%, the silk fibroin peptide powder was, for example, 0.7 g / cm ³ or more, and the ratio of the cold water easily soluble peptide (α structure) was 50% or less.

In accordance with Example 3 Example 1 was dissolved silk material in anhydrous salt concentration in terms of 40% calcium nitrate _{(Ca (NO 3) 2 ·} 4H 2 O), then dialyzed to produce a silk fibroin aqueous solution.

This was concentrated or diluted to the concentration shown in Table 3, and an aqueous solution of sodium hydroxide was added to this to make a 0.3N-NaOH solution.
After heating at 5 ℃ for 3 hours with stirring, neutralize with 5N hydrochloric acid to adjust the pH.
= 6.8. This was decolorized with activated carbon, passed through and desalted with an ion exchange resin to obtain a light yellow transparent silk fibroin in peptide aqueous solution.

This was freeze-dried according to Example 1 to obtain powdered silk fibroin peptide. Table 3 shows the average degree of polymerization, the bulk density, the ratio of the peptide readily soluble in cold water (α structure), and the crystallinity.

Also in the case of hydrolysis with alkali, the silk fibroin peptide obtained by freeze-drying is almost amorphous in the case of the present invention as in Example 1, and the bulk density is 0.2 to 0.7 g.
A powder having a value of / cm ³ and being preferable in various senses was obtained.
On the other hand, if the average degree of polymerization of the peptide is 2 or less, the bulk density will be high even if the silk fibroin peptide concentration after freeze-drying is 2%.
0.2 g / cm ³ or less, and a concentration of 4 as in Examples 1 and 2.
When it exceeded 0%, the bulk density was 0.7 g / cm ³ or more.

Although a slight degree of crystallinity was observed in 3- (6) of the present invention, in the case of the present invention, a silk fibroin peptide having substantially 50% or more α structure was obtained.

Example 4 Calcium nitrate (Ca (NO ₃ ) ₂ .4H ₂ O) 4 was prepared according to Example 1.
A silk raw material was dissolved at a concentration of 0% and then dialyzed to prepare an aqueous silk fibroin solution. Silk fibroin concentration 10%
Was added to the mixture and added at the concentration of bioprase / conc shown in Table 4, and reacted for 4 hours while raising the temperature from 20 ° C to 70 ° C. Then, treatment, purification and lyophilization were carried out according to Example 1 to obtain a silk fibroin peptide in powder form.

Table 4 shows the average degree of polymerization, bulk density, proportion of cold water easily soluble peptide (α structure) and crystallinity of the obtained silk fibroin peptide.

From the results in Table 4, the amount of enzyme for silk fibroin was 0.
It is understood that the amount is preferably from 01 to 10% by weight, more preferably 0.02% by weight or more, and if 10% by weight or more, the effect is poor in terms of economy. Even in the case of 4- (8) in which no enzyme was added, the α structure was 50% or more and the bulk density was 0.2 g / cm ³ or more.

In accordance with Example 5 Example 1, magnesium nitrate _{(Mg (NO 3) 2 ·} 6H 2 O)
Was melted by heating as it was, the silk raw material was dissolved therein, and then dialyzed to obtain an aqueous silk fibroin solution. In this aqueous solution, various proteolytic enzymes shown in Table 5 (enzyme activity 150,000 PU
N / g) is added to silk fibroin at 1%, and the temperature is 20 ° C.
Then, the reaction was carried out for 4 hours while raising the temperature to 70 ° C. Then, after treatment and purification according to Example 1, a silk fibroin peptide concentration was adjusted to 20%, and this was lyophilized to obtain a powdered silk fibroin peptide. Table 5 shows the average degree of polymerization, the bulk density, the ratio of the peptide readily soluble in cold water (α structure), and the crystallinity of the obtained silk fibroin peptide.

Claims (14)

[Claims] 1. A powdery silk fibroin peptide having an average degree of polymerization of ³ to 600 and a bulk density of 0.2 to 0.7 g / cm ^{3 with} an average particle size of 10 to 40 μm, at least 5
A substantially amorphous powdery silk fibroin peptide consisting of 0% by weight of an α structure which is easily soluble in cold water. 2. The powdery silk fibroin peptide according to claim 1, which has an average degree of polymerization of 5 to 100. 3. The powdery silk fibroin peptide according to claim 1, which has an average degree of polymerization of 10 to 40. 4. The powdered silk fibroin peptide according to claim 1, which has an α structure of at least 75% by weight. 5. The powdery silk fibroin peptide according to claim 1, wherein the α structure is substantially 100% by weight. 6. The silk fibroin solution in the silk fibroin solution obtained by dissolving the silk fiber in an aqueous medium is hydrolyzed, or the silk fibroin solution has a silk fibroin concentration of 2 to 40% by weight, The method for producing a powdery silk fibroin peptide according to the above-mentioned claim (1), characterized in that the pH is adjusted to 4.5 to 7.5, followed by freeze-drying. 7. The method for producing powdery silk fibroin peptide according to claim 6, wherein the aqueous medium is calcium hydrochloride or nitrate or magnesium hydrochloride or nitrate. 8. The powdered silk fibroin peptide according to claim 6 or 7, wherein the silk fibroin concentration of the silk fibroin solution is adjusted to 2 to 40% by weight by dialysis. Manufacturing method. 9. A dialysis is carried out using a multilayer membrane structure or a hollow fiber focusing structure satisfying [membrane surface area (cm ² )] / [priming capacity (cm ³ )] ≧ 10. A method for producing the powdered silk fibroin peptide according to the range (8). 10. The method for producing a powdered silk fibroin peptide according to claim 6, wherein the hydrolysis is carried out using a protease, an acid or an alkali. 11. The method for producing powdery silk fibroin peptide according to claim 10, wherein the proteolytic enzyme is bioprase, papain, trypsin or chymotrypsin. 12. A protease for silk fibroin
The method for producing a powdery silk fibroin peptide according to claim (10), which is used by adding 0.01 to 10.0% by weight. 13. The method for producing a powdery silk fibroin peptide according to claim 10, wherein the acid has a concentration of 0.3 N or less. 14. The method for producing a powdery silk fibroin peptide according to claim 10, wherein the alkali has a concentration of 0.3 N or less.