Extraction of harp seal gastric proteases and their immobilization on chitin

Gastric proteases from seal stomach were isolated following homogenization, extraction, centrifugation and ammonium sulfate precipitation/fractionation. The crude seal gastric proteases (SGP) were stable in acid conditions with optimum stability at pH 3.0, but were unstable in the alkaline range. The crude SGP possessed excellent temperature adaptability with relative activities of 70 and 90% at 5 and 25 °C, respectively. The activity of crude SGPs was retained up to about 40 min incubation at 70 °C. The isolated SGP were immobilized on glutaraldehyde-treated chitin. The immobilized SGP exhibited optimum performance at pH 2.0, were most stable at pH 4.0 and had a 90 h half-life in a column with continuous operation for haemoglobin hydrolysis at room temperature. The native SGP clotted milk rapidly at pH 5.8 to 6.6; however, immobilized SGP had a lower milk-clotting activity.