| Selenium (Se) is an essential micronutrient for humans, it has many important physiological functions, such as enhance immunity, anti-cancer, anti-oxidation and so on, which has important significance to the human body. Inorganic Se species added in the environment can be transformed into organic Se species through the biological metabolism of the plants. Crops is a major source to increase Se nourishment level in the low-Se regions. Se can be ingested in two different forms: inorganic Se compounds and organic Se compounds in the plants. Generally, organic Se compounds (e.g., seleno-amino acids and selenoproteins) are higher bioavailable and lower toxic than the inorganic Se compounds. Mung bean sprouts have high protein content and rich nutrition. The inorganic Se species in the environment can be transformed into organic Se species effectively through the process of sprouting of mung bean.The aim of this study was to cultivate the Se-enriched mung bean sprouts in the laboratory, and to study the effect of Se on the physiological property through the growth of mung bean sprouts, determine the total Se species, soluble Se species and protein Se species in mung bean sprouts. High performance liquid chromatography coupled with mass spectrometry (HPLC-MS) was used to identify and quantitate the Se-MeSeCys, Se-Met and Se-Cys contained in Se-enriched mung bean sprouts, the conclusions were as follows:1,Low concentration of Se could promote the growth of mung bean sprouts, when the concentration of Se was less than 5 mg/L, Se appeared to provide a positive benefit of the germination rate and lengths for the mung bean sprouts compared with the control group. When the concentration of Se was more than 5 mg/L, the germination rate began to decrease. When Se concentration was 12 mg/L, germination rate was reduced by 30%, and length of hypocotyl and radicles was reduced by 36.7% and 31.6% respectively. The result of coomassie brilliant blue G-250 method showed that the protein content range in the Se-enriched mung bean sprouts is from 14% to 19%. Se can be beneficial to increase the protein content, and then promote the synthesis of nutrition in mung bean sprouts.2, Graphite Furnace Atomic Absorption Spectrometry (GFAAS) was used to analysis total Se content in Se-enriched mung bean sprouts, with HNO3 as the digestive reagent. Different dosages of digestive reagent were used to study the effect of the sample. The results showed that, total Se in the mung bean sprouts increased with the different concentrations of Se added in the solution, and reached the maximum value 7275 μg/kg when the Se concentration was 12 mg/L. But high concentration of Se could produce toxic for the growth of mung bean sprouts, and restrain the growth of the mung bean sprouts.3, Deionized water, HC1, NaOH and Tris-HCl were used as extraction solution to extract the soluble Se and GFAAS was used to determine the Se content in the mung bean sprouts. The results showed that, the sequence of soluble Se content in mung bean sprouts was as follows:acid soluble fraction> alkali soluble fraction> Tris-HCl soluble fraction> water soluble fraction. All dissolved Se content increased with increasing concentration of Se. The acid soluble fraction, alkali soluble fraction, Tris-HCl soluble fraction and water soluble fraction of Se accounted for 50%-55%, 35%-45%,30%-35% and 20%-30% of total Se concentration, respectively. As the results, acidic medium was advantageous for the extraction of Se, thus it is more easily to absorb Se for human body.Alkali soluble acid isoelectric point method was used to extract the soluble Se in the Se-enriched mung bean sprouts, the lye concentration, material/liquid ratio, extraction time, extraction temperature and isoelectric point were optimized to research the effect on protein extraction ratio. The result showed that the optimal condition forextraction was:extract concentration,0.20mol/L; material/liquid ratio, 1:50; extraction time,90 min; extraction temperature,44℃ and isoelectric point, pH=4.8. The soluble protein was extract under the optimized extraction conditions. The protein precipitation was digest by microwave digestion instrument and determine the Se content by GFAAS.The results showed that the Se content in the protein increased across the concentrations of Se in the solution, reached the maximum of 1710μg/kg, and accounted for 23.5% of total Se content. Therefore, a high concentration of Se can increase not only the Se content in protein, but also the proportion of total Se content in protein.4, High Performance Liquid Chromatography coupled with Mass Spectrometry (HPLC-MS) was used to identify and quantitate the Se-MeSeCys, Se-Met and Se-Cys was in Se-enriched mung bean sprouts. Different fragmenting voltages (Frag) and collision energy (CID) were optimized for each sample and the best extraction condition was chosen to measure the intensity of the eluted seleno-amino acids in multiple reaction monitoring (MRM).The results showed that Se-MeSeCys was the major seleno-amino acid in Se-enriched mung bean sprouts, while Se-Met and Se-Cys were both minor species, accounting for 5% of the total Se content. Therefore, organic Se can be transformed into inorganic Se effectively through the biotransformation of mung bean sprouts, which could provide a good source of dietary Se supplement to increase the Se level in low Se region. |
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