Identification of protease enzyme in salep orchid tubers, and investigation of the usability of the enzyme in casein and gluten hydrolysis

Abstract

In recent years, due to many diseases transmitted from animals to humans (coronavirus disease, severe acute respiratory syndrome, mad cow, and bird and swine flu), consumers are concerned about the use of protease enzymes derived from animal sources in the production of food products. These concerns have increased the demand for protease enzymes of plant origin. The fact that very few of the protease enzymes used in the production of foodstuffs are produced from plant sources has led researchers to seek a new source of plant-based protease. In the present work, the protease enzyme was isolated from the tubers of the salep orchid (Dactylorhiza osmanica) by ammonium sulphate precipitation and size exclusion chromatography. The isolated protease had an optimal pH of 6.5 and an optimal temperature of 48°C. The Km value was 8.22 µM. The molecular mass of the enzyme was 31 kDa. The enzyme retained its 100% activity up to 21 h at 40°C. At 50°C, the enzyme maintained its 100% activity for up to 4 h. The isolated protease acquired from the salep orchid tubers hydrolysed α-, β-, and κ-casein, and formed new peptides larger than 15 kDa. The isolated enzyme is known to be effective in milk clotting, which is the first step of cheese making, and might also contribute to the production of cheese with specific flavours. However, the protease extracted from the salep orchid tubers cannot hydrolyse gluten at the same level.