1. Division of Environmental Engineering Science, Gunma University, Kiryu, Japan
2. Graduate School of Engineering, Gunma University, Kiryu, Japan
3. Department of Materials Science and Engineering, School of Materials and Chemical Technology, Tokyo Institute of Technology, Tokyo, Japan
4. Silk Materials Research Unit, National Agriculture and Food Research Organization (NARO), Tsukuba, Japan
5. Kyoto Municipal Institute of Industrial Technology and Culture, Kyoto, Japan
6. Faculty of Molecular Chemistry and Engineering, Kyoto Institute of Technology, Kyoto, Japan