The Journal of Silk Science and Technology of Japan
Online ISSN : 1881-1698
Print ISSN : 1880-8204
ISSN-L : 1880-8204
Current issue
Displaying 1-17 of 17 articles from this issue
Treatise
  • Tomohiko Hananouchi, Masaaki Okajima, Kaho Suzuki, Saori Ohori, Tika T ...
    2022 Volume 30 Pages 31-43
    Published: 2022
    Released on J-STAGE: September 27, 2022
    JOURNAL FREE ACCESS

      A size detector made of titanium was developed in the 「6A Project」, which aimed to achieve the highest rank of raw silk quality. Although the functions of the detector were highly regarded, it had a problem with respect to practical use. Silk reelers pointed out that, unlike in the case of the glass size detector, dirt and stains could not be checked because the insertion state of threads was not visible.

      In order to address this problem, a new hybrid-type size detector was developed, which consists of a plane gauge made of a transparent plastic material, and a titanium gauge with a level difference equivalent to the thickness of a spacer (a film inserted between the two round plates (gauges), which together function as a disk -type size detector).

      Comparison and examination of the characteristic evaluations made by the different detectors showed that a surface-treated polycarbonate hybrid-type size detector was promising for practical use, for the following reasons: (1) the target size could be controlled with a roundup denier adjustment device, (2) errors between the individual detectors were eliminated because a spacer was not required, and (3) easier maintenance, due to its ease of assembly and disassembly.

    Download PDF (921K)
  • Masaaki Aoki, Yasushi Tamada
    2022 Volume 30 Pages 45-54
    Published: 2022
    Released on J-STAGE: September 27, 2022
    JOURNAL FREE ACCESS

    This study investigated the gelation mechanism of regenerated silk fibroin (RSF) aqueous solution during storage. Gel permeation chromatography analysis of the RSF solution after various times in storage revealed decreasing molecular size by molecular cleavage according to the storage time. Rapidly decreasing molecular size was observed near the gelation time. However, no gelation was observed in the case of an RSF aqueous solution containing only lower molecular weight molecules. Particle analysis of an RSF aqueous solution during storage showed formation of around 100–400 nm diameter particles by storage. The RSF aqueous solution viscosity decreased according to the storage time. The secondary structure of RSF freeze-dried the aqueous solution at various storage times was measured using FTIR analysis, which indicated an increasing β-sheet structure ratio as the storage time progressed. Taken together, we proposed the gelation mechanism of RSF aqueous solution during storage and discussed the proposed mechanism.

    Download PDF (1570K)
  • Yutaka Kawahara, Masaki Yamamoto, Tomohiko Hananouchi
    2022 Volume 30 Pages 55-61
    Published: 2022
    Released on J-STAGE: September 27, 2022
    JOURNAL FREE ACCESS

    Weibull analysis was applied to the tensile strength data of the silk cocoon threads obtained from the Bombyx mori silkworms of 83 breeds reared in three seasons: early autumn in 2010, late autumn in 2010, and early winter in 2012. Results showed that the shape factor obtained from the Weibull analysis was almost independent of the changes in the fineness of raw silk, which was apparently related to the peculiar fiber formation process of the Bombyx mori silkworm that showed only slight dependence on the spinning speed. However, peeling of the sericin-layer or over degumming of the raw silk fibers would result in a decrease of the shape factor.

    Download PDF (825K)
  • Taichi Sonoda, Naohiro Shimada, Keiko Takaki, Eiji Kotani
    2022 Volume 30 Pages 63-73
    Published: 2022
    Released on J-STAGE: September 27, 2022
    JOURNAL FREE ACCESS

    Many proteins have been shown to be encapsulated in cypovirus (BmCPV) protein microcrystal polyhedra. However, a method to control the BmCPV polyhedron portion for encapsulation has not been elucidated. Herein, we report the development of a method to produce multi-layered BmCPV polyhedra. For this, isolated cultured Sf21 cells that stably expressed BmCPV polyhedra encapsulation signal (H1)-fused EGFP (H1-EGFP) were obtained, in which baculovirus carrying both BmCPV polyhedrin and H1-DsRed produced high percentage (91.56%) of multi-layered BmCPV polyhedra with H1-EGFP encapsulated in the inner layer and H1-DsRed in the outermost. In addition, we generated transgenic silkworms with cells, in which the H1-EGFP was continuously expressed and the recombinant baculovirus produced 82.33% of multi-layered BmCPV polyhedra. These results indicate that foreign proteins already abundant in the cells before the start of BmCPV poryhedrin crystallization are encapsulated in the inner layer of the polyhedra, whereas foreign proteins expressed simultaneously with BmCPV polyhedrin were encapsulated in the outermost layer. Dissolving the multi-layered polyhedra in buffer (pH 9.5) revealed the first phase of the outermost H1-DsRed release, followed by the second phase of inner H1-EGFP release, demonstrating that the multi-layered BmCPV polyhedra can release encapsulated proteins with different timings, which can be applied to the development of drug delivery carriers applicable for tissue engineering.

    Download PDF (852K)
  • Yaxi Tian, Masatoshi Iga, Hiromi Tsuboi, Hidetoshi Teramoto
    2022 Volume 30 Pages 75-85
    Published: 2022
    Released on J-STAGE: September 27, 2022
    JOURNAL FREE ACCESS

    Bombyx mori silk is a sustainable bioresource with diverse applications in textiles, electronics, and medicine. It attracts much research interest because of its mechanical toughness, controllable biodegradability, electrical properties, and broad biocompatibility. A novel silk type, AzidoSilk, was developed based on genetic code expansion (GCE) methodology: an emerging biotechnology that can expand the repertoire of amino acid building blocks used for protein biosynthesis. An azido-bearing synthetic amino acid, 4-azidophenylalanine (AzPhe), is incorporated in AzidoSilk. Because the azido group in AzPhe can be modified selectively with functional molecules by click chemistry reactions, AzidoSilk can be a versatile platform for producing functional silk-based materials for various applications. Unfortunately, low production of AzidoSilk by a current transgenic B. mori line hampers its practical applications. This report describes breeding of a novel transgenic B. mori line for mass production of AzidoSilk using a conventional backcrossing method from the current transgenic line H06 to the high silk-producing wildtype strain MCS4. The resultant line H06-MCS4 established after five times of backcrossing produced 2.6 times greater amounts of AzidoSilk per larva with 25% increased productivity. Although AzPhe incorporation in silk fibroin decreased by 21%, clear and selective modification of azido groups in AzidoSilk were verified using click chemistry reaction tests. The AzidoSilk fiber was prepared using standard machine reeling. Its mechanical properties were found to be equivalent to those of normal silk fiber from MCS4. The generation of H06-MCS4 will open possibilities for producing AzidoSilk on an industrial scale.

    Download PDF (538K)
  • Tetsuya Iizuka, Eiji Okada
    2022 Volume 30 Pages 87-92
    Published: 2022
    Released on J-STAGE: September 27, 2022
    JOURNAL FREE ACCESS

    Light-emitting diodes (LEDs) have become widely used in recent years. We investigated the deterioration of quality of silkworm artificial diets because of LED exposure. First, feeding tests were performed on first-stage larvae on artificial diets irradiated with blue, red, green, and white LEDs at 50 µmol/m2/s for 96 hr. Results showed that the larvae fed well on the artificial diet under dark conditions, while they did not feed on the artificial diet irradiated with LEDs of various types. Next, feeding tests of artificial diets irradiated with different levels of white LED indicated that artificial diets irradiated with 1 µmol/m2/s white LED for 96 hr were not consumed, whereas artificial diets irradiated with 5 µmol/m2/s white LED were consumed. Of the silkworm larvae, 100% fed on the artificial diet irradiated with 10 µmol/m2/s white LED for 12 hr, whereas the percentage of larvae feeding on the artificial diet irradiated for 24 hr dropped to about 14%. These results indicate that white LEDs are useful for rearing if the irradiance and irradiation time are considered.

    Download PDF (536K)
  • Munguti Peter Muindi, Fumiko Yukuhiro, Sosaku Ichikawa, Hidetoshi Tera ...
    2022 Volume 30 Pages 93-103
    Published: 2022
    Released on J-STAGE: September 27, 2022
    JOURNAL FREE ACCESS

    We have succeeded in producing nanoparticles consisting solely of intact high-molecular-weight sericin protein, which has molecular weight comparable to that of the native state. Such intact sericin was obtained from the “Sericin Hope” silkworm variety bred in Japan. Nanoparticles were prepared using a so-called anti-solvent diffusion method by which the aqueous solution of intact sericin was added dropwise to ethanol (EtOH). Morphological transmission electron microscopy (TEM) observations were performed of nanoparticle sericin dispersed in the 75% EtOH aqueous solution, which is a mixed solution produced by dropping an aqueous solution of sericin onto EtOH. Effect of the concentration of dropped sericin on particle size was evaluated using dynamic light scattering (DLS) measurements. The particle size became uniform at concentrations lower than 1.0 wt%. For concentrations <1.0 wt%, the average size of nanoparticles was 10–30 nm, and lower concentrations were associated with larger nanoparticles. Nanoparticle-dispersed EtOH aqueous solutions were colorless and transparent. The transparency remained unchanged for at least one month. The particle morphologies also remained unchanged. The nanoparticle structure, which was maintained even in water after EtOH was removed, was maintained even after freeze-drying. Results of SDS-PAGE show that the same molecular weight as those of native sericin was maintained in the nanoparticles. The intact or partially degraded high-molecular-weight sericin proteins constituted the nanoparticles obtained in this study.

    Download PDF (534K)
  • Yurika Saito, Takeshi Yokoyama, Yoshitaka Takahashi
    2022 Volume 30 Pages 105-116
    Published: 2022
    Released on J-STAGE: September 27, 2022
    JOURNAL FREE ACCESS

    This study focuses on the hitherto overlooked “Straw House for Silkworm Rearing” and aimed to find new examples of appropriate technological development by the Sericultural Experiment Station and Sericultural Training Institute in the 1887-1930s.The structure of Straw House for Silkworm Rearing was analyzed by using models and photographs from the period that remain in the Nature and Science Museum, Tokyo University of Agriculture and Technology. As a result, it was found that the structure was equipped with ventilation and heating systems that enabled the advanced sericultural technology of the time. In addition, the average temperature of the standard rearing method proposed by the Ministry of Agriculture and Commerce was 70 degrees Fahrenheit (21.1 degrees Celsius), and tests were conducted assuming rearing by a married couple. This result overturns a frequently raised hypothesis that the contribution of government sericultural educational institutions to the improvement of practical sericultural techniques during the Meiji period was lower than that of private educational institutions. In particular, the air adjustment mechanism of the Simple Straw House for Silkworm Rearing is suggestive for the development of non-electrified sericultural equipment in the present age, and contributes to solving the problem of sericultural diffusion to remote areas and poor farmers in the present age.

    Download PDF (1572K)
feedback
Top