苜蓿中金属肽酶对青贮过程中蛋白降解的作用

为探讨金属肽酶在苜蓿青贮过程中对蛋白的降解作用，以苜蓿（Medicago stativa L.）绿汁发酵液模拟青贮发酵过程，添加金属肽酶抑制剂后，测定发酵后第0.5、1、1.5、2、2.5、3、4、5、7和14天时绿汁发酵液的蛋白组分。结果表明，在苜蓿发酵液发酵过程中添加金属肽酶抑制剂能够降低pH值、非蛋白氮、游离氨基酸和氨态氮含量，增加乳酸含量；发酵第14天时，抑制剂处理组非蛋白氮、游离氨基酸和氨态氮质量分数为483.98 g/kg TN，256.98 g/kg TN和26.11 g/kg TN，与对照组相比分别降低28.92%，38.59%和67.08%。金属肽酶对苜蓿发酵液蛋白降解起着一定的作用；添加金属肽酶抑制剂能够提高发酵液发酵品质。

Effects of metal endopeptidase in alfalfa on protein degradation of ensiling process

Effects of metal endopeptidase on protein degradation of alfalfa silage was investigated in this study. After adding metal protease inhibitor EDTA in the previously fermented alfalfa juice (PFJ), samples of each treatment were opened on day 0.5, 1, 1.5, 2, 2.5, 3, 4, 5, 7 and 14 d and the protein components were analyzed. Results showed that non-protein nitrogen (NPN), NH3-N, amino acid nitrogen (AA-N) and pH value in EDTA treatment significantly decreased during ensiling process, but lactic acid concentration increased. On day 14, the concentrations of NPN, NH3-N and AA-N of EDTA treatment were 483.98 g/kg total nigrogen (TN), 256.98 g/kg TN and 26.11 g/kg TN, which decreased by 28.92%, 38.59% and 67.08% respectively compared with the control. Metal endopeptidase plays a role on the degradation of NPN during proteolysis process of ensiled alfalfa to some extent. Adding metal endopeptidase inhibitor can improve the fermentation quality of alfalfa silage.