Japanese oak silkmoth (Antheraea yamamai) cocoons were treated by proteinase K solution (dissolved by phosphate buffer) or heated by 0.05% (w/v) NaHSO3 solution as traditional method. Cocoons were reeled by automatic reeling machine to get silk fiber. Fiber and silk that couldn’t reel as silk fibers (thin inner shell layer that is no longer able to be reeled and brushing waste that arisen by brushing to pull out the cocoon filament from the cocoon surface and feeding to the automatic reeling machine) were measured their weight and calculated the ratio of silk fiber and total weight of cocoon shell to know the reeling efficiency (recovery). According to the t-test, there was significant difference between at the recovery of silk fiber cooked by using proteinase K (average ± standard deviation (SD): 72.4 ± 3.8%) and traditional method (average ± SD: 63.0 ± 7.9%). Reeled fibers were also taken the tensile testing and t-test. The results showed that there was no significant difference between the average of tensile strength [N] per denier [d] of fibers cooked by using proteinase K (average ± SD: 46.1 ± 5.2 mN/d) and traditional method (average ± SD: 44.9 ± 4.8 mN/d). These results suggest that the method of using proteinase K solution to the cocoon of A. yamamai for reeling makes possible to get silk fiber more efficiently with same mechanical property as that of traditional method. This can be expected to use as efficient method for reeling silk from wild silkmoth cocoon.
Backcross of Japanese oak silkmoth Antheraea yamamai (A. yamamai) was undertaken to breed a strain with greater silk production capacity by hybridizing a strain showing a high fertilization rate (SUB-52) and a strain showing heavy cocoon weight (SUB-11). By repeating backcross from 2010 to 2018, we obtained and stored backcross strain (Bn; n represents the number of generations) from third generation (B3) to seventh generation (B7). Comparing SUB-52, SUB-11 and each Bn by statistic method showed that B6 was superior to other strains in terms of silk productivity. Although cocoon weight and cocoon shell weight in the latest backcross strain B7 was significantly higher than that of SUB-52, there was no significant difference between B7 and their recurrent parent SUB-11. We consider that B7 was getting closer to SUB-11 and appropriate backcross should be limited until B6. As for future research, we plan to improve the fertilization rate by using Bn for hybridization.
A stable and reproducible preparation of A. pernyi fibroin (APF) aqueous solution is an important theme for using APF for medical applications. We experienced gelation and aggregation of APF during its preparation when following reported literatures. We reconsidered the whole preparation process to prepare AFP aqueous solution. The pretreatment and degumming process of the cocoons didn’t have influence. More than 15 M LiSCN was required for complete dissolution. The dialysis time was sensitive on gelation and shorter time was an improvement for the aqueous solution stability. Finally, addition of small amount of Ca2+ was effective to improve stability of the aqueous solution.
The Antheraea pernyi silk fibroin (A. pernyi fibroin) has been studied as an expecting material for medical use with good cell proliferation in tissue engineering thanks to its RGD sequence in its molecule that improves cell adhesion. We developed an improved process to make the aqueous solution stably without gelation during the dialysis process and reported it in our previous paper. In this study, we reported the characterization of our A. pernyi fibroin film fabricated from the aqueous solution prepared by the new process, and we compared the results with previously reported A. pernyi fibroin films. The secondary structure of A. pernyi fibroin was determined by ATR-FTIR measurement of the film, and the surface morphology was observed by AFM. The physicochemical properties of the surface were measured by contact angle and zeta potential. In order to evaluate the cell compatibility, cell adhesion and proliferation test, and cell mobility measurement were performed. The characteristic properties and cell behaviors on our A. pernyi fibroin film were then reported.
We have been using silkworms as biological materials such as the breeding of it, observation / dissection, crossing experiments of crossing tests. Sericin and fibroin of silkworm cocoons are processed into powder and film and are being researched and developed as new materials. However, their chemical properties have not been treated as experimental teaching materials. In this study, we tried developing new chemistry teaching materials focusing on the chemical properties of sericin and fibroin, and conducted a practical chemical experiment and a questionnaire survey.
Sericin was fractionated into two by the difference in solubility between hot water and alkaline aqueous solution. According to the scanning electron microscope (SEM) image, we confirmed the presence of sericin in cocoon thread treated with hot water. The fibroin aqueous solution produced from cocoons tends to undergo gelation, so long-term preservation is difficult. Therefore, to make it a practical chemistry experiment sample, we examined long-term storage methods of fibroin aqueous solution at low temperature. We confirmed that the fibroin solution frozen at -80 °C maintained the state of the aqueous solution even after thawing for over 6 months. The results of questionnaires to people who participated in chemical experiments using silkworm cocoons suggested that experiments on the chemical properties of sericin and fibroin could be expected to raise awareness about methods other than clothing fibers.
Differences in raw silk cohesion and physical properties between usual and low temperature cocoon cooking methods were assessed. Cocoons of a commercial silkworm race, Gunma × 200, were used for these analyses. Physical properties such as stress and strain were slightly but significantly lower in raw silk made from low-temperature cooked cocoons compared to the properties of usually cooked cocoons, although no significant difference was found for Young’s modulus. The raw silk surfaces of usual and low-temperature cooked cocoons after reeling showed no significant difference, and binding of cocoon filaments was observed. However, the cohesion of raw silk made from low-temperature cooked cocoons was significantly lower. To investigate factors affecting the reduction of cohesion, further analyses were performed. Results revealed that both detergent and alkaline agent used in low-temperature cocoon cooking method adversely affected raw silk cohesion. In addition to cohesion, reeling tests were performed to ascertain the influence of detergent and alkaline agent used with cocoons during low-temperature cooking. Reeling tests revealed that alkaline agent treatment lowered the raw silk percentage of cocoon and the neatness, although those properties recovered when treated concomitantly with detergent. Furthermore, results demonstrated that reelability was improved when cocoons were treated with a combination of detergent and an alkaline agent.
The ration system of silk textile existing in Tokamachi textile production area was abolished after World War II, in June 1949, which allowed subsequent free economic activities. Since then, the system distributing all textiles produced in Tokamachi textile production area from textile manufacturers to wholesalers in gathering places for mass-consumption areas and finally to retailers through brokers was created and continued until around 1980. The system then has changed. While manufacturers of piece dyed fabrics, which are rather big in the area, have shifted to direct dealing, those of yarn-dyed fabrics, which are small and medium-sized in the area, still have made deals via brokers. The paper examines the changes in the distribution system and the current situation.
This study aims to analyze a vibration mode of fibroin in silk fiber quantitatively, and to create a new identification method of fibers using terahertz transmission spectroscopic analysis.
Terahertz spectroscopic analyses of 9 types of silks (4 types of domesticated silks and 5 types of wild silks) were carried out. Although it was difficult to distinguish between the domesticated silks, distinct spectral difference was obtained between the domesticated silks and wild silks. This may be originated from the difference of intermolecular linkage.
Terahertz spectroscopic analysis of fibers from boiled cocoons of domesticated silkworms has been demonstrated. The result revealed that the condition of boiling affected terahertz spectra, and the difference of the spectra was thought to be due to residual amount of sericin when boiled, indicating the possibility of evaluating the residual content of sericin in silk fibers.
The author conducted a restoration study of the 18th-century French court costume and is studying aesthetic sense and dyeing technique. Because costumes are being restored based on detailed research data such as composition data such as costume patterns and weaving techniques, weaving methods, etc. There is no previous study mentioning the reason such as silk costumes are lightweight.
In this study, from the survey of textiles in the Rococo era of domestic and overseas museums, it was hypothesized that the texture properties of this court costume texture might be related to silkworm varieties, and for four years from 2012, after obtaining the Grants-in-Aid for Scientific Research, we restored court costumes from breeding of the original race of European silkworm variety. First of all, we bred Sevenne white of European silkworm cultivar, reeled the raw silk, weave a white cloth and made a dress. Next, again breeding it, restoring the fabric of Kasuri made of natural dyestuffs, making it into a court costume．These studies demonstrate that the characteristics of the court costume ‘light, three-dimensional form, and soft’ properties are attributable to the characteristics of the European silkworm cultivar Sevenne White, and due to differences in silkworm varieties. We clarified the importance of fiber properties and the aesthetic sense required in the Rococo era. The characteristic is clearly to have them as a result of the experiment, it became clear that the difference in the form of the dress is caused by the fiber characteristics of the silkworm variety.
Hot air-drying, a widely used method for cocoon drying, uses multi-band progressive cocoon-drying machines. For hot air-drying, 115°C is recommended on contact with the cocoon. The finishing temperature should be reduced gradually from 60°C during hot air-drying.
Because the fluorescent color is eliminated by high-temperature treatment, the harvested cocoons were dried at 60°C for 24 hr. Fluorescently colored silk, cocoon drying, and cooking all constitute bottlenecks that impede efficient production. To alleviate those bottlenecks, we used a vacuum cocoon cooking machine for fluorescently colored silk. The machine has been semiautomated and scaled up to overcome the productivity constraints. Nevertheless, cocoon drying of the fluorescent colored silk was not improved. This report describes the performance of reeling tests and color observations of freeze-dried cocoons produced by fluorescently colored silk strains and a standard strain. Results demonstrate that the cocoon color of the fluorescent silk strains faded slightly and that the percentage of reelability was decreased.
To understand the relationship between structure and mechanical property of silks, it is necessary for understanding their hierarchical structure over wide range of structural scales. In this study, hierarchical structure of Indian golden wild-silk, Antheraea assamensis (A. assama) silk, was investigated by wide-angle and small-angle X-ray scatterings (WAXD and SAXS). SAXS results revealed presence of nanofibril structure made up of periodically repeated β-sheet crystalline and amorphous domains. The correlation function analysis for SAXS data clarified each domain thickness in the periodic structure. The crystalline domain thickness was quantitatively ascribed to the 12 ~ 13 alanine residues in polyalanine blocks and the amorphous one to the roughly 40% slacking non-polyalanine blocks in the tandem repeating motifs of A. assama silk determined recently by Gupta et al. On the basis of quantitative quantitative WAXD and SAXS data, a detailed hierarchical structure model for A. assama silk was proposed.
In order to realize technological history of the French type silk-reeling process in modern Japan, we carefully examined 68 academic documents and technical books for raw silk production which published from the Meiji era, the Taisho era to the Showa era. As a result of analyzing geometrical structure and technological parameters such as distance between hook and surface of reeling basin, distance between hooks, number of crossing, length of crossing, angle of getting uncrossed threads, it was found that transition of technique for the French type silk-reeling cross and process can be classified into three period: the European technology introduced period, the adaption period and the Japanese technology established period. Furthermore, we analyzed experimental data in “Tomoyori Souchi Shiken” published by Mr. Mitani to know influences of technological parameters on the quality and productivity of raw silk. We installed density of crossing as a new parameter to realize the phenomenon of the French type silk-reeling cross. As a result, it seems that the French type silk-reeling cross includes a complexity of geometrical structure and a nonlinearity of each technological parameters. This situation might have been difficult to optimize the process conditions in the era. It turned out that factors of the technological transitions were attributable to adaptation of Japanese silk mills to the introduced Western style technology, quality of raw material cocoon and changes of the global market structure and needs.
Recently, there are demands for silkworm races which are superior in quantitative traits, easy to rear, and characterized by cocoon thread like thick and thin filament and double cocoons. Focusing on the fact that the physical properties of raw silk are different among silkworm races, we measured the strength, elongation and Young’s modulus of the silk for the regional type of the races possessed by NARO in order to establish a new breeding basis. As a result, the average value in Chinese native races was highest in strength, the elongation was in Improved European races, and the Young’s modulus was highest in European native races. In the comparison of individual race, there were races showing the maximum value of 6 kgf/d in strength or the value of 38.5% in elongation. In order to add these superior properties to silkworm races, we made a crossbred generation (F1) between existing type and high strength type and investigated inheritance on high strength properties. F1 with a parent of high strength or thin thread race has high value in strength, and F1 with a parent of thick thread is high value in elongation. These findings indicate that there is a moderate correlation between strength extension and size of thread. In this study, based on the results, we tried crossbreeding between existing race and high-strength strain and tried creating material for new silkworm race with excellent strength.
Incorporation of an unnatural amino acid bearing an azido group, 4-azido-L-phenylalanine, into the non-repetitive regions of silk fibroin has enabled its facile modification using azido groups as chemical handles. We have previously investigated crosslinking of fibroin using a bifunctional chemical crosslinker and found that the crosslinking reactions hardly proceeded between fibroin molecules. The difficulty of crosslinking was probably due to the steric constraint between fibroin molecules as well as the low abundance of azido groups. In this study, we investigated crosslinking of fibroin having an approximately 2.5-fold increase in azido groups. The results showed that the fibroin with an increase in azido groups was more prone to crosslinking. We infer that the azido groups exhibit different reactivities according to their incorporated positions in the non-repetitive regions, and that the increased incorporation of azido groups improved the likelihood of azido groups being in the positions most advantageous for crosslinking.