Microencapsulated alkaline protease with enhanced stability and temperature resistance for silk degumming

Abstract

Alkaline protease plays a critical role in enhancing protein digestion and absorption but is sensitive to environmental factors, particularly pH value and temperature. Only under appropriate conditions, alkaline protease can catalyze the cleavage of amide bonds in macromolecular proteins. To enhance the stability and temperature resistance of alkaline protease (AP), microencapsulation using ethyl cellulose (EC) was employed. EC, known for its biocompatibility and biodegradability, was used as the wall material in an oil phase separation method, with dichloromethane serving as low boiling point solvent. The microencapsulated alkaline protease (Mic-AP) was characterized using scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR) and thermogravimetric analysis (TGA). The enzyme activity was evaluated using casein as the substrate. It was found that optimal conditions for Mic-AP preparation were m_core:m_wall of 1:1, emulsifier of 5 wt%, and volatilization temperature of 40 °C, yielding up to 90 % microencapsulation efficiency, the enzyme activity up to 17,000 U/g. Microencapsulation of alkaline protease not only enhances its stability but also preserves its natural properties. It is proved that Mic-AP exhibits improved temperature resistance. Furthermore, the enzyme activity of Mic-AP is higher than that of AP at high temperature of 60 °C, 80 °C, 100 °C and 120 °C. Therefore, Mic-AP has significant potential for high-temperature applications, such as the feed industry and silk degumming.