JPH0767687A - Production of water-soluble silk fibroin - Google Patents

Abstract

PURPOSE:To provide a process for producing a water-soluble silk fibroin, capable of easily controlling the molecular weight of the silk fibroin between 1,000 and 5,000 and giving a water-soluble silk fibroin having excellent properties and useful as a raw material for foods, cosmetics, etc. CONSTITUTION:This process for the production of a water-soluble silk fibroin comprises the hydrolysis of silk with dilute alkali and the hydrolysis of the product with proteinase.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION Industrial field: A method for producing water-soluble silk fibroin from silk and the peptide are used for foods, cosmetic materials and the like.

[0002]

[Prior art]

BACKGROUND OF THE INVENTION Silk such as cocoon or silk thread has been finely pulverized and used for cosmetics and food materials. Further, it has been proposed that the silk is hydrolyzed with an alkali to obtain an aqueous solution of fibroin and / or an aqueous solution of sericin, and the aqueous solution is used as a food (Patent Application Publication No. 1-256351).

[0003]

However, it is difficult to control the progress of hydrolysis by the conventional methods. Also, when hydrolyzed with a mineral acid, the amount of mineral acid used is large and the amount of alkali required for its neutralization is large, so the amount of salt produced is large and the removal of acid after coloring or decomposition is complete. There is a drawback that it becomes complicated.

[0004]

The present invention is a method for producing water-soluble silk fibroin, which comprises hydrolyzing silk with a dilute alkali and further hydrolyzing it with a protease.

The present invention will be described in detail. The silk of the present invention can be used in any of silk products such as cocoon, silk cotton, silk thread or scrap silk thread. However, cocoon or scrap silk thread is economically suitable, and high purity obtained by removing proteins or sugars of mulberry and the like. Silk is the best. Alkali means a pH of 8 to 1 in an aqueous solution.
Alkali substances of 4 can be used. Specifically, Na2 CO
There are 3, NaOH and KOH.

The present invention will be described more specifically. As for silk, the central silk fibroin is covered with strong silk sericin,
Therefore, first, the silk is immersed in water and hydrolyzed at pH 8 to 14 to decompose the silk sericin. Decomposition varies depending on the type of alkali used and treatment conditions, but is 2 to 6 hours with dilute alkali (pH 8 to 13.5), preferably pH 9
It heat-processes for 3 to 5 hours by -12. For example, Na
Heat treatment with a 2-5% aqueous solution of OH for 3-4 hours. If a strong alkali is used, neutralize with acid as necessary. After the treatment, silk sericin is hydrolyzed to be gum-like or resin-like, and fibroin is sol-like or water-soluble. Therefore, silk sericin and its decomposition products can be easily separated. The separation can be carried out by an ordinary individual liquid separation treatment, for example, filtration, centrifugation or the like.

The sol or water-soluble silk fibroin obtained as the filtrate is further subjected to proteolytic enzymes at 35 ° C to 60 ° C for 24 to 72 hours, preferably 40 ° C to 55 ° C.
Fermentation is carried out at 36 ° C. for 36 to 48 hours for hydrolysis to obtain an aqueous silk fibroin solution. Depending on the conditions, silk fibroin is retained at a molecular weight of about 1000 to 5000. The silk fibroin aqueous solution can be used for various purposes as it is, but if necessary, it is treated with activated carbon for purification,
It is also possible to remove water to obtain powder. For example, an aqueous silk fibroin solution is freeze-dried or spray-dried to obtain powdery water-soluble silk fibroin.

The obtained water-soluble silk fibroin has a molecular weight of about 1,000 to 5,000, is tasteless and odorless, and has excellent moisturizing properties, degradability and water solubility, and is particularly absorbed in the small intestine.
It becomes an excellent functional food with good digestibility. When used for ice cream, drinks, etc., it has excellent foaming properties, smoothness, and aroma retention. When used in cosmetics and shampoo, it has excellent water retention and hydrophilicity. In the two-step hydrolysis with alkali and enzyme of the present invention, the progress of the reaction can be easily controlled and adjusted, and the molecular weight of the resulting water-soluble silk fibroin can be arbitrarily adjusted, and thus the product has excellent properties.

Example 1 A scrap cocoon 400 was placed in a round bottom flask equipped with a reflux condenser.
Grams and 300 ml of a 2.5% aqueous solution of caustic soda were added and the mixture was boiled and heated until the solid content disappeared (3 hours 30 minutes). Next, add about 50 ml of 4% hydrochloric acid to adjust the pH to about
Neutralized to 7 and filtered. The filtration residue is a solid resin material,
It was silk sericin. The filtrate was concentrated to 150 ml to obtain a viscous silk fibroin aqueous solution. To this, 3 g of a protease was added, and the mixture was kept at 45 to 50 ° C. for 48 hours for fermentation and hydrolysis. Then, the mixture is heated at 85 ° C. for 30 minutes to inactivate the enzyme and desalted through an ultrafiltration membrane to obtain a transparent silk fibroin aqueous solution (water-soluble silk fibroin aqueous solution).
Got The obtained silk fibroin aqueous solution was further freeze-dried to obtain flaky water-soluble silk fibroin powder.

[0010]

EFFECTS OF THE INVENTION The progress and control of hydrolysis are easy, and the water-soluble silk fibroin obtained has excellent properties.

Continuation of front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display area A61K 7/00 J

Claims (4)

[Claims] 1. A method for producing water-soluble silk fibroin, which comprises hydrolyzing silk with a dilute alkali and further hydrolyzing it with a protease. 2. The method according to claim 1, wherein the hydrolysis is carried out with a dilute alkali at pH 10 to 13.5 for 30 minutes to 3 hours. 3. The average molecular weight of silk fibroin according to claim 2, which is 1,000 to 5,000 by the protease.
To hydrolyze until 4. Production of water-soluble silk fibroin obtained by the method of claim 3.