Eco-friendly enzymatic dehairing of goatskins utilizing a metalloprotease high-effectively expressed by Bacillus subtilis SCK6

Abstract

In this study, an extracellular metalloprotease (EMPr) from Bacillus sp. LCB14 was cloned, successfully expressed in Bacillus subtilis SCK6, and utilized to dehair goat skins in leather-making processes. Through optimization of fermentation conditions, the expression level of EMPr reached 6973 U/mL after 72 h of incubation. Then the crude enzyme was purified 6.30 fold through a three-step purification process of centrifugation, dialysis and SP Sepharose Fast Flow. The purified protease EMPr was established by 12.5% SDS-PAGE and showed 40.08 kDa. It exhibited highest activity 77,302 U/mg at pH 6.5 and 50 °C respectively. Protease activity was slightly enhanced by Li+ and K+. Interestingly, the protease activity was enhanced by the surfactants, such as, Tween 20, Tween 80, SDS, and Triton X-100 respectively. The dehairing experiments showed that the crude EMPr completely dehaired goatskins during 6 h at 33–35 °C without use of sodium sulfide. The enzymatic dehaired belt showed well opening up of fiber structure and the collagen was not damaged. Therefore the protease EMPr displayed great potential application in dehairing process without using sodium sulfide.