Degumming raw silk by a halotolerant metalloprotease isolated from metabolites of Vibrio sp. LA-05

Abstract

The crude sample of a halotolerant metalloprotease produced by Vibrio sp. LA-05 was systematically investigated as a silk degumming agent. The experimental results showed that the required time, when the sericin was completely eliminated, varied with the incubation temperatures. The sericin was almost completely removed when raw silk was co-incubated with the crude protease solution (490 U/mL) at 45 °C for 3 h. The results of SEM, thermal analyses, tensile properties and regenerated silk fibroin indicated that the properties of silk fibre degummed with crude protease were superior to those of the traditional Na2CO3 method. Furthermore, SDS-PAGE analyses revealed that the sericin could be hydrolyzed into small peptides by protease during the degumming process. Sericin proteolysis product (SPP) recovered from the protease degumming solution displayed dose-dependent ABTS˙+ scavenging activity and ferric ion reducing capacity. The antioxidant activity of SPP was significantly better than that of sericin recovered from the Na2CO3 degumming solution. The findings in this study suggest that this halotolerant metalloprotease may be developed to an eco-friendly, energy- and resource-saving silk degumming agent.