Abstract
Red dragon fruit is one of famous fruits in Indonesia. High level of red dragon fruit consumption is followed by the high amount of the fruit peel waste. Red dragon fruit peel contains many important compounds, one of them is alkaline protease. Therefore, red dragon fruit peel can be used as an alternative to get an alkaline protease. This research has some purposes, i.e. to characterize the best pH and temperature for the alkaline protease, to determine the most efficient purification process for the protease and to determine the molecular size of alkaline protease. This research began with obtaining the crude extract of alkaline protease from red dragon fruit peel, followed by pH and temperature characterization, partial purification, i.e. ammonium sulfate precipitation 20%-80%, dialysis and Ion Exchange Chromatography using Biorex Cation Exchange Resins, and finally SDS PAGE. The result showed that the optimum temperature for alkaline protease activity was 60°C and the optimum pH for alkaline protease activity was 8. In the final step of purification, namely ion exchange chromatography (IEC), the specific activity value was 6,2 x 10-4 µmol/µg.min, indicating a 3,29 fold purification of the initial crude extract. In this research, the alkaline protease showed a molecular mass of 23 kDa.