| This study took the soybean as raw carrier. Enrich selenium in it by treating soybean with selenium solution of different concentrations and by way of soaking and spraying. Biological accumulation of selenium was realize during the process of soybean sprouting, The protein of selenium-enriched soybean sprouts is isolated from the selenium-enriched soybean sprouts by the method of alkali-solution and acid-isolation. And content of total selenium were determined by using a fluormetric method; the content of organic selenium is analyzed by the method of still-placed and oozing-out the inorganic selenium. The effect of selenium applied at different levels including different concentration and cultivation time on the ability to accumulate selenium during the soybean germinated was studied. The result indicates that Se concentration and cultivation time have determinant effect on the content of selenium enriched in soybean sprouts. The optimum content of total selenium in soybean sprouts is 42.46μg/g. Se content of soybean proteins extracted is 21.24μg/g. When treated with 10μg/ml selenium solution in soybean sprouts and cultivation time is 120h.REE as selenium-enriched accelerant was utilized for improving Se accumulation in the soybean sprouts because of outstanding biology function. In this paper, The REE selenium-enriched soybean sprouts were prepared by adding different concentrations of rare earth La3+,Ce3+,Nd3+ into different concentrations of selenium cultivation solution and The REE selenium-enriched soybean proteins was isolated, determine result show that REE can promote ability of soybean sprouts to absorb Se and increase the content of total selenium and organic selenium, but the impact of different rare earth element has discrepancy upon the kind and concentration of REE. The most effective rare earth element is La. Next is Nd, last is Ce. The result indicates that La3+ promotes the uptake of selenium in the soybean sprouts and Se organic degree at low concentrations. Content of total selenium and organic selenium in selenium-enriched soybean sprouts were both raised gradually when the concentrations of La3+ is below 6μg/ml, but decreased when the concentrations of La3+are above 7μg/ml. The same trend occur to Se content of the protein components extracted from Selenium-enriched Soybean sprouts treated with La3+. The highest Se content 65.83μg·g-1 and Se content of protein 26.13μg·g-1 were all observed at concentrations 6μg·mL-1 La3+, which was respectively increased by 55.06% and 23.02% as apposed to that from soybean sprouts treated without La3+.Data from Infrared spectrum scanning and Analysis of Amino Acids constituents show that Se of Selenium-enriched protein was found to be incorporated chemically into the protein structure rather than being bound physically to cell wall. And total content of amino acids in proteins extracts was increased by 18.86% as opposed to that from common soybean sprouts; especially content of glutamic acid was remarkably increased by 35.54 %. Furthermore, REE can further increase the total content of amino acids in the soybean sprouts. Antioxidant analysis shows that ability of selenium-enriched proteins to scavenge hydroxyl and superoxide radicals was increased effectively, especially for the superoxide radicals.The content of rare earth is analyzed. And the data indicates that the contents of rare earth in the samples increase with the increase of the concentration of rare earth added in the cultivation solution. When the concentrations of rare earth added in the soybean sprouts is 7μg·mL-1, the highest content of rare earth in the soybean sprouts and protein is 30.35μg·g-1 and 45.37μg·g-1 respectively, Which are both below the tolerable upper intake level of rare earth for adults12mg·d-1～120mg·d-1. In general, rare earth is an effective and safe selenium-enriched accelerant for soybean protein and of expansive application foreground in food field.
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