固定化胰蛋白酶亲和层析法制备低STI残存大豆分离蛋白质

聚苯乙烯阴离子交换树脂(GM201)经预处理除去杂质后先与戊二醛(2—6％)反应,再与胰蛋白酶(5000u/mg,8—10mg/mL,pH 8.0)反应即制得固定化胰蛋白酶。此法得到的固定化胰蛋白酶具有良好的热稳定性,贮藏稳定性和操作稳定性,可用于工业化目的。脱脂豆粉经萃取(PH9.0)后,稀释4倍,在pH5.0下沉淀分离出大豆球蛋白,然后用酸性水(pH5.0)洗涤两次,并进行碱溶与酸沉淀两次,即可将大豆分离蛋白质的STI残留降低到1.85％,比活性降到1u/mg以下。最后再用固定化胰蛋白酶亲和层析,就可以除去大豆分离蛋白质中残留的STI。

Preparation of Low-STI Soybean Protein Isolates by Affinity Chromatography on Immobilized Trypsin

A new method for the preparation of low-STI soybean protein isolates was developed which included preliminary separation of STI from. soybean protein extract by acidic precipitation followed by affinity chromatography on immobilized trypsin.Polystyrene anion exchange resin GM 201,which had been purified to remove impurities, was treated first with glutaraldehyde (2-6%), then coupled with trypsin (5000 u/mg, 8-10mg/mL, pH8.0). Immobilized trypsin thus obtained was more stable on storage and to heat-treatment than solubilized trypsin and had good operational stability. Defatted soybean flour was extracted with water at pH9.0,the extract was diluted with water and precipitated with acid at pH5.0. The precipitate, mainly soybean globulins, was washed twice with acidic water at pH5.0. Resolubilization with water at pH 9.0 and precipitation with acid at pH5.0 were repeated twice. The STI content in the soybean protein isolates was reduced to 1.85% with specific activity below 1u/mg. After affinity chromatography on immobilized trypsin,the STI in the soybean protein isolates was completely removed.