• Journal of Sericultural and Entomological Science
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• v.27 no.1
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• pp.47-50
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• 1985

The physical properties of graft polymerized silk fibre were investigated with various vinyl monomers. 1. The graft polymerization of styrene and methyl methacrylate onto raw silk reduced the tenacity and elongation of raw silk due to fixation of sericin covering silk fibre in, but the styrene grafting was more effective for sericin fixation of raw silk than the methyl methacrylate one. 2. The water absorbability of glycidyl methacrylate grafted silk increased 14.6% greater than that of methyl methacrylate grafted silk at the same degree of grafting polymerization. 3. The degree of grafting polymerization was increased mostly with ethylene glycol methacrylate. The water absorbability of ethylene glycol methacrylate grafted silk was higher than that of glycidyl methacrylate or ethyl acrylate grafted silk. But the grafted silk fabric increased the fabric flexural rigidity which was negatively related with the favorability of fabric hand-touch, as compared with that of nongrafted silk fabric. 4. The evenness of graft polymerization could be improved by agitating the polymerization bath at the fixed interval by reducing the inter size deviation of grafted silk skein and the thickness deviation of grafted silk fabric.

• Microbiology and Biotechnology Letters
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• v.47 no.4
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• pp.487-497
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• 2019

Fetal Bovine Serum (FBS) is an essential substance added to animal cell culture medium. However, its composition is unclear causing problems such as development of an immune response when cultured cells are transplanted into the human body. In this study, silk sericin, silk fibroin, and hemolymph obtained from silkworms were added to the cell culture medium in order to determine if it can replace FBS. After establishment of the cell culture, cell proliferation and expression levels of cell growth-related genes were compared with those of control cells (cells cultured in the medium with 10% FBS). Results showed that the test group treated with silk fibroin extracted from a Korean silkworm variety, Kumokjam could replace 10% FBS. In addition, expression levels of cell growth related genes such as Fibronectin and TGF-β1 increased significantly in cells cultured using silk fibroin, depending on the concentration used in cell adhesion and cell proliferation [24]. To date, no studies have been conducted to find a replacement for FBS. Thus, this study was carried out to develop a substitute for FBS by using silkworm-derived alternatives such as silkworm hemolymph, silk sericin, and silk fibroin, which are cheap and have various physiological effects, cell promoting effects, and can be mass produced.

• Journal of Fashion Business
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• v.8 no.5
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• pp.31-40
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• 2004

The purpose of this study is to investigate the change of the physical properties, bending and luster properties, which are related to the touch and appearance of silk fabrics modified by the degumming process. The silk has long been known as one of the most elegant and soft textile materials. The raw silk yarn, or cocoon bave, spun from the spinneret, is rather stiff due to the sericin covering the two fibroins together. The sericin can be removed during a degumming process. The removal of the sericin would result in remarkable change in the physical properties of the raw silk fabrics, including luster of the fabrics, which process parameters could possibly be utilized to adequately control the silk fabric properties. The KES(Kawabata Evaluation System) is a testing methodology that has been used with considerable success for predicting the hand and tailorability of apparel fabrics. This study uses one of the KES, bending tester, to measure the bending properties of the silk fabrics degummed for specified period to change the physical/mechanical properties of the fabric. The KES bending measurement revealed that the bending rigidity decreased for both the warp and weft direction of the silk fabrics with the increase of the degumming period. It has been shown in this study that the some of the hand-related physical properties, including the bending rigidity, drapability, and luster, could be modified with the change in the degumming period.

• Journal of Sericultural and Entomological Science
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• v.51 no.1
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• pp.68-72
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• 2013

Fibroin and sericin are natural proteins obtained from cocoon and one of the spotlight materials for medical device. Medical device made of these proteins also has the advantage that this material is biodegradable in to amino acid. In this study, we prepared silk sponges using fibroin, sericin and additives. The characterizations of the silk sponges such as morphology, stability, and blood absorbency were observed. The structural stability of the silk sponge decreased significantly by increasing sericin contents. The effect on the concentrations of ethanol to induce crystallization was observed to be superior to 70% ethanol. Structural stability of silk sponges containing additives was very lower than those not containing additives. The blood absorbency of the silk sponges was found to be excellent, regardless of the composition of sericin and fibroin. The resilient power of these sponges was also very good, in spite of the repeated soaking and drying. Therefore, we expect that the silk sponges can be used medical supplies such as plastic implants and hemostatic cotton.

• Journal of Sericultural and Entomological Science
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• v.30 no.1
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• pp.33-39
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• 1988

In the case of white cocoon, the fluorescence colors are classified as a yellowish fluorescence cocoon(Y.F.C.) and a violet fluorescence cocoon(V.F.C.) by exposing to ultra-violet ray. Accordingly, experiments were carried out to investigate the difference of sericin behaviors between Y.F.C. and V.F.C. by measuring the sericin solubility, surface tension and viscosity of the sericin solution. Also, the reelability of two different type of cocoons was investigated in the silk reeling process. The results were summarized as follows; 1. The sericin solubility of Y.F.C. shell is higher than that of V.F.C. shell with the dissolution temperature and time. It is shown that the sericin solubility curves of Y.F.c. and V.F.C. are similar in shape, but the difference of sericin solubility between Y.F.C. and V.F.C. is more significant at higher bath temperature. 2. The initial sericin dissolution curves of Y.F.C. and V.F.C. cocoon shell can be divided by four parts within the range of dissolving time from 5 minutes to 60 minutes. The initial dissolution velocity of Y.F.C. shell is faster than that of V.F.C. but the velocity difference is negligible after 30 minutes of dissolving time. 3. The gelation of V.F.C. sericin solution is faster than that of Y.F.C. at early stage(in the range of 15 minutes to 60 minutes). 4. In the silk reeling process, the reelability of Y.F.C. is better than that of V.F.C. with about 11%. This is mainly due to the higher sericin solubility in Y.F.C. followed by the fast dissolution velocity.

• Journal of Sericultural and Entomological Science
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• v.45 no.1
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• pp.34-45
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• 2003

Silk was treated with calcium hydroxide for degumming at different treatment times, temperatures and Ca(OH)$_2$ concentration to optimize degumming conditions in this thesis. After degumming, soluble and insoluble sericin were seperated and then the soluble sericin was characterized by measuring the average degree of polymerization (D.P.), lysinoalanine (LAL) content, DSC, and by amino acid analysis. And degummed silk fibroin was characterized by measuring tenacity and SEM. Degumming loss was increased by increasing the treatment time and temperature until about 30 minutes. After then, a slight difference was found along with treatment times at the Ca(OH)$_2$ concentrations of 0.07% and 0.1% solutions. After degumming, insoluble sericin ratio on degumming solution was increased by increasing treatment temperature at Ca(OH)$_2$ 0.04% solution. At the concentration Ca(OH)$_2$ of 0.07%, a soluble ratio was almost 100% regardless of treatment time and temperature. At the beginning of treatment, insoluble ratio was high at Ca(OH)$_2$ 0.1% solution but it was decreased by increasing treatment time. At the Ca(OH)$_2$ concentration of 0.04%, D.P. of soluble sericin was maintained as a constant value of 10 at 100$^{\circ}C$ although treatment time was increased. However, at 80$^{\circ}C$ and 90$^{\circ}C$, it was hard to prepare a soluble sericin having a constant D.P. by increasing treatment time. At the Ca(OH)$_2$ concentration of 0.07%, D.P. was almost 10 irrespective of treatment temperature and time. Soluble sericins with high D.P. of 20∼30 were obtained at 0.1% and 100$^{\circ}C$. LAL was not detected in soluble sericin. As the results of amino acid analysis, it showed that Ca(OH)$_2$ degumming reduced the contents of hydroxy amino acids like Ser., Thr. and Tyr. In DSC analysis of soluble sericin, endothermic peak by thermal deformation and pyrolysis showed at 189$^{\circ}C$ and at 299$^{\circ}C$, respectively. The tenacities of degummed silk were 15∼30% lower than that of raw silk. And it was decreased with increasing treatment time. From the morphological study, the thickness of degummed silk fibroin became thinner by increasing degumming loss. The roughness of a silk fibroin surface was appeared as treatment concentration was increased.

• International Journal of Industrial Entomology and Biomaterials
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• v.8 no.2
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• pp.195-200
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• 2004

Trypsin can be immobilized on silk fibroin fiber (SFF) by introducing several spacer arms, such as ethylene diamine (ED), bovine serum albumin (BSA) and silk sericin (SS). Direct immobilization on silk fiber (SFFGA) has low activity because of the steric hindrance between the trypsin and substrate. The introduction of spacer arms onto SFF-GA can enhance the activity of trypsin by reducing the steric hindrance. When ED is used as a spacer arm, the activity of trypsin has increased but its stability decreased due to the increased hydrophobicity of SFF. BSA and SS, as a spacer arm, have better results in both activity and stability. SFF-BSA shows some decrease in the specific activity due to improper immobilizatin. SFF-SS maintained 90% of its initial activity even after 12 hrs incubation at $50^{\circ}C$. In the case of repeated hydrolysis of silk sericin with immobilized trypsin, SFF-GA and SFF-ED lost 50% of their initial activity right after first run, whereas SFF-BSA and SFF-SS maintained 80% of their initial activities even after 5 runs. Higher operational stability is due to increased hydrophilicity of SFF by introducing hydrophilic spacer arms such as BSA and SS. The high content of serine in SS increases the hydrophilicity of SFF resulting the best results among other spacer arms.

• Journal of Sericultural and Entomological Science
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• v.41 no.3
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• pp.185-195
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• 1999

This study was carried out to improve the skin care property of the polyester fabric by finishing with sericin. It was known that skin care function, anti-oxidation, anti-tyrosinase activity and anti-elastase activity can be achieved from sericin finish. But, the moisture regain of the finished fabric was measured simply, because the major cause of the discomfort from polyester fabric has been anounced to be wetness. The effects of various treatment conditions on the properties of the finished fabric were measured, and obtained results were as follows: 1. The moisture regain at 40$^{\circ}C$ 90% RH were increased with the sericin uptake increasing. while it was not significant for the effects on the moisture regain depending on the treatment conditions like the degree of polymerization and treatment concentration of the binder. The moisture release of the fabric having sericin uptake 1%, 2% was faster than non treated fabric. The change of the moisture regain of the finished fabric from 40$^{\circ}C$ 90% RH to room temperature was 4∼5 times higher than that of knitted cotton fabric. 2. The frictional static charge was decreased with the degree of polymerization of the binder increasing. While the sericin uptake and treatment concentration of the binder were not significant. 3. The whiteness value of the fabric was slightly decreased by finishing with sericin and binder. In that cases, W values of the finished fabrics were above 90 while that depending on the degree of polymerization of the binder was not significant. 4. The major cause of the yellowness of the finished fabric was proved to be catalyst. The yellowness of the finished fabric with sulfur containing catalyst was lower than that with amine group containing catalyst. 5. The effects of the treatment concentrations of the cross-linking agent, catalyst and drying time on the wash durability were not significant.

• International Journal of Industrial Entomology and Biomaterials
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• v.36 no.1
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• pp.10-14
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• 2018

A photo-crosslinkable sericin hydrogel has been prepared by introducing methacrylate groups on sericin. Lysine was the amino acid for methacrylation and the degree of methacrylation was increased with the amount of methacrylic anhydride added. When the concentration of methacrylic anhydride was 20% of sericin, 0.635 mmol/g of methacrylate group could be introduced. The storage modulus of sericin hydrogel was increased proportionally with the degree of methacrylation. However, the swelling ratio of sericin hydrogel decreased with the increase of methacrylation.

• Journal of Sericultural and Entomological Science
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• v.2
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• pp.1-31
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• 1962

The purpose of this treatise is to prove the presence of cystine in silk fiber through wide sampling throughout all the sericultural processes of Bombyx mori.; also to show that disulfide cross linkages exist in the silk fiber. The conclusions reached were as follows: 1. Crystalline cystine was obtained from silk fibroin using Folin's Method. 2. Analytical data showing the cystine content of silk fiber and its related materials were obtained using Sullvan's Method as follows: Material Percent Cystine A. Mulberry leaf protein 0.175 B. Silkworm egg 0.33 C. Silkworm Body, matured, fat extracted, without silk gland 0.41 D. Silk gland, matured 1.23 E. Silkworm feces none F. Silkworm pupa, fat extracted 0.30 G. Silkworm moth, fat extracted 0.60 H. Raw Silk 0.22 I. Fibroin 0.175 J. Sericin 0.30 3. The presence of cystine in the silkworm was substantiated the existence of 0.175 % methionine in mulberry leaves and 0.12% methionine in the silk gland. 4. Part of the sulfhydryl compounds in the silk gland is believed to transfer to serine and methionine, with the former being secreted into the liquid silk finally as silk fiber and the latter used for nutritive purposes in the growing of silk gland tissue. 5. The cystine content is variable by mulberry species, silkworm species, sex, breeding process, and other culturing environments. 6. Hybrid silkworms require more nutritive amino acids for effective growth than the original parents, and secrete less of them as silk fiber. 7. From such an observation, the amino acid composition of silk fiber is believed to be fairly flexible. Cystine if included in the amorphous part of the fiber, especially in sericin. 8. The result from enriching the silkworm diet with pure cystine or wool cystine did not result in any advantage, therefore it is believed that the natural cystine and methionine contents in the mulberry leafaregoodenoughforsilkwormnutrition. 9. The disulfide cross linkage in silk fiber was verified by using the Harris Method. Contraction took place following the treatment of the fiber with various salts and acids. Comparisons were made with wool fiber. 10. During these experiments, the fibrious structure of silk fiber and the net-globular liquid form were photographed microscopically. It is believed that the globules of liquid silk are net-formed by the inter attraction of the OH ion of the globular peptide and the H ion of water as shown by the hair cracking behavior of the film. The net-globular protein precipitation from the mulberry protein solution showed that mulberry is a proper diet for the formation of fibrous protein in the silk fiber. 11. The significance of the presence of cystine in silk fiber as emphasized in this paper should result in modification of the general conception that cystine is absent from this fiber. NOTICE: A part of this treatise was presented at the annual Korea Sericultural Society meeting held in 1961.