| Soy peptide is a peptide mixture obtained from a soy protein by acid or enzymatic hydrolysis or separation, purification. It consists mainly of small peptides. The protein content of soybean peptide is about 85%, and its amino acid composition is almost exactly the same as soy protein. Its balance of essential amino acids is good, and the content is also abundant. At the same time it was discovered that many small molecular weight peptide in the human body through the digestive tract without being hydrolyzed, can be directly absorbed by the body to use, and has lowering blood pressure, digestible, easy to absorb, the promotion of energy metabolism and anti-obesity effects, but also to eliminate fatigue, enhance muscle stretching and anti-allergy and so on.Lead and its compounds in the environment is everywhere. Especially in recent years its wide application in industry, makes lead poisoning has occurred frequently. Lead poisoning is manifested mainly as influenced the function and life of erythrocyte, induced the derangement of begetative nerve, hurt the composition of the long-lasting protein and cranial nerve, harmed the function of renal tubule, and so on.In this study, soy protein isolate, as the raw material was used to prepare soybean peptide with enzymatic matter. The soybean peptides were separated using gel filtration chromatography. Then we choose the antioxidant most soybean peptide applied to the lead-eliminating drink fluid, and study its synergy effects of promotion in eliminating lead.1. The optimization for process conditions of papain hydrolyzing soy protein. In this study, we used heating method to do pre-processing of soy protein isolate. The results showed that for isolated soy protein, the best pretreatment temperature is 85℃, pretreatment time is 20min. Under these conditions the degree of hydrolysis of soy protein isolate increased 38.13%. Besides, using a single factor experiment we studied the effects of five factors, as the hydrolysis temperature, pH, substrate concentration, enzyme concentration and hydrolysis time, on the degree of hydrolysis of soy protein isolate and anti-oxidation. Based on the single factor experiment, a five-quadratic orthogonal experimental design, and SAS statistical analysis were used to optimize isolating process parameters of the papain hydrolyzing soy protein. Optimization results were that: hydrolysis temperature was 56℃, pH=7.0, substrate concentration was 5.0%, the amount of enzyme was 4%, and hydrolysis time was 4h. In the hydrolysis conditions, anti-oxidant value of the hydrolysis liquid reached 4120.33μmol/L.2. The research of separating soybean peptide with gel filtration chromatography. Using sephadex G-25 gel filtration chromatography to separate soybean hydrolysates, we obtained four kinds of peptide components, and the relative molecular weight of the four peptide components was: SP1 in 74130Da above, SP2 of the range of 12540~74130Da, SP3 of the range of 1011~12540Da, SP4 of 148~1011Da. The anti-oxidation activity of these four kinds of peptide components was measured. And it is found that SP4 has the strongest antioxidant activity. Through the amino acid composition analysis, peptide SP4 is composed of 16 kinds of amino acids. Using reversed-phase HPLC analysis we find that SP4 contains three peptide peaks.3. Preparation of lead-eliminating drink fluid. The effect of sodium selenite, calcium gluconate, sodium dihydrogen phosphate, and konjac flour on the rate of lead-chelating was studied. The change in the scope of each single factor was determined. Based on the single factor experiment, calcium gluconate, sodium dihydrogen phoSPate and konjac flour was selected to do three factors and three-level orthogonal test. Using SAS8.2 statistical analysis for data processing, the best ratio of the stimulative lead-eliminating drink fluid was obtained: the additive amount of calcium gluconate was 7.5g/L, the additive amount of sodium dihydrogen phoSPate was 2.5g/, and the additive amount of konjac flour was 0.4%. The soy peptide prepared above was added to stimulative lead-eliminating drink fluid. With the rate of lead-chelating as indicator, it is showed that the additive dosage of soy peptides is 6%, when suitable.4. Animal experimental verification of soybean antioxidant peptides promoting lead-eliminating effect. According to body weight, 180 clean grade"Kun Ming"rats with 18~20g were divided into nine groups: blank group, negative control group, positive control group, drinking fluids with high-dose group and drinking fluids + peptide with high-dose group (0.4mL) drinking fluid with middle-dose group and drinking fluids + peptide with middle-dose group (0.3mL) and drinking fluid with low-dose group and drinking fluids + peptide with low-dose group (0.2mL). In addition to the blank group, the other groups containing lead acetate 0.24% in deionizer water solution were used to establish a preventive lead poisoning model. Six dose groups filled stomach with experimental liquid, the positive control group was given DMSA solution, and the negative group was given the deionizer water. When 20 days passed in the experimentation, the tail blood once, lead content were tested; in the administration of 40d at the end times, fasting 24h, got blood from eyes, broken neck to put to death, collected each group rat liver, femur and blood, and lead content was measured.The content of lead in the blood, liver and bone of the six-dose group tended to drinking liquid + peptide in the middle-dose group and high-dose group are prominently, followed by drinking fluids middle-dose group and high-dose group. This indicates that soybean peptide has a coordinating function to eliminate lead, and the functional drink fluid has a good lead-eliminating effect. And for the lead levels in the blood, liver and bone, drinking fluid + peptide middle-dose group is better than the high-dose group and has a lower cost. This indicates that dose effect relationship between the proportions of factors is strict within a certain range and comprehensive drinking fluid + peptide with middle dose group is the best dose group.
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