A Pilot Study on Stable Isotope Compositions of Bombyx Mori L. and Saturniidae Silks: Comparison of Species, Influence of Degumming Method and Tracing the Provenance of Bombyx Mori Silk

Cocoons of non-mulberry feeding silkworms from nine genera of the Saturniidae family were degummed and analyzed with regard to their 13C/12C and 15N/14N signature. The analyses reveal that the isotopic signature probably depends strongly on the habitat of the silkworms and the available forage plants. Furthermore, δ13C, δ15N, δ2H and δ18O values of Bombyx mori L. (BM) cocoons and degummed silks from China, Turkey, Germany, Italy and the Swiss Confederation were determined, and correlations of the isotopic signature with climatic and geographical parameters were examined. A negative correlation was found between the altitude and the δ13C and δ18O values of BM cocoons. A principal component analysis of the isotopic signature reveals differences between silks from low- and high-altitude regions. Thus, stable isotope ratios of light elements are confirmed as a promising tool to trace the provenance of BM silks. Studies on silks treated with various acids, bases, detergents and/or organic solvents of different polarity show that both the sample pretreatment and the degumming method have no or only a minor influence on the δ13C and δ15N values. However, δ18O values can change by up to 2.4 ‰ and δ2H values by up to 16.2 ‰, depending on the treatment method.