The degradation behaviors of Thai Bombyx mori called Samrong and Nanglai silk fibroins exposure to protease enzymes; protease XIV, protease XXIII and α-chymotrypsin type II were studied in this work. The degradation behaviors were expressed by their weight loss, morphological and secondary structure changes as well as thermal properties. Samrong showed higher percentage of weight loss than Nanglai. SEM micrographs indicated that silk fibroin were de- stroyed and showed many holes on their fiber surfaces. All of silk samples were increasable destroyed when exposure to the protease enzyme for long incubation period. With thermal analysis, both silk fibroin presented the thermal stability in the same profile. The result suggested that the selected silk fibroin should be composed of similar pattern of amino acids and their ratios. However, the protease susceptibility of each silk fibroin slightly varied in case of morphology observation. This might be affected by their genetic variety.
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