Valorization of avian by-products such as turkey (Meleagris gallopavo) proventriculus in the preparation of milk clotting enzymes constitutes an alternative to commercial rennet. The clotting enzyme of Meleagris gallopavo has been prepared by ammonium sulfate at 50% saturation followed by purification by cation-exchange fast protein liquid chromatography (FPLC), and determination of the clotting protease activity performed on milk incubated at 35 °C. The clotting fractions are concentrated and dialyzed against Tris/HCl pH 7.0 through a membrane with cutoff 8000 Da, and separated by anion-exchange FPLC. The coagulating fractions obtained by cation-exchange chromatography are also separated by reversed-phase high-performance liquid chromatography, which revealed only one fraction able to coagulate milk. Electrophoresis analysis revealed a band with apparent molecular mass of 36.5 kDa and seemed to correspond to pepsin-like enzyme according to primary sequence alignment analyses. Maximal clotting activity was obtained for optimal conditions of temperature of 55 °C and pH 5.4.

在制备牛奶凝结酶过程中，对禽副产品（如火鸡（Meleagris gallopavo）原胃）进行增值处理构成了商业凝乳酶的替代品。鸡血lea的凝结酶硫酸铵是通过以50％饱和度的硫酸铵制备，然后通过阳离子交换快速蛋白液相色谱（FPLC）纯化，并测定在35°C孵育的牛奶上的凝结蛋白酶活性。浓缩凝结级分，并通过截留值为8000 Da的膜针对Tris / HCl pH 7.0进行渗析，然后通过阴离子交换FPLC进行分离。通过阳离子交换色谱法获得的凝结部分也通过反相高效液相色谱法进行了分离，这表明只有一种馏分能够凝结牛奶。电泳分析显示，根据一级序列比对分析，表带的分子量为36.5 kDa，似乎对应于胃蛋白酶样酶。