| High Fischer ratio oligopeptides with a special amino acids composition of high branched chain amino acids (BCAA) and low aromatic amino acids (AAA) could play important physiologic functions on liver disease patients, high expend patients and athletes. CGM was a by-product in a wet corn starch plant, which was suitable for preparation of high Fischer ratio oligopeptides for its high branched chain amino acids content. It was utilized as raw material to prepare for high Fishcher ratio oligopeptides by enzyme methods. Protein of CGM isolating, protease and hydrolysis condition selecting, hydrolysis process controlling, ultrafiltration and adsorption condition selecting were studied in this dissertation. The relative molecular mass (Mr) range and Fischer ratio were studied, too. The main results indicated:1. The basic processing was affirmed. Key facets concerned pre-treat of CGM, hydrolysis of protein of CGM, isolating of high Fischer ratio oligopeptides.2. Pre-treating was necessary for high Fischer ratio oligopeptides preparation. It concerned with 3 facets. First, decolor of material. The parameters of the pigment extractin: adding acton into CGM in proper ratio of substance to solvent (1:3), extracting 4h at 30℃, repeating this operation 3 times were the economical, high qualitative way. Second, remove starch. Decolor CGM mixed with water at 1:1, cultured Ih at 90℃, then added 1.0% a-amylase at pH 5.5, 60℃, after it didn't change to blue in the iodine experiment, given 2.0% p-amylase to culture 8h at pH 4.8, 45℃, protein of CGM with 83.5% protein content was obtained. Third, increase the solubility of protein of CGM. Dealing with alkaline, rising temperature and adding reductant Na2SO3 were good way. Adding 0.10% Na2SO3, heating 15 minutes at pH10.0, 90℃ was applied to increasing solubility to 14.24%, the index of nitrogen solubility (NSI) to 12.70%.3. The Mr range of hydrolysates was far away from predetermined only treated by one protease. Two proteases were used in hydrolysis. 2709 alcalase had powerful enzymatic hydrolysis. Results indicated that the optimum parameters for 2709 alcalase were 5.0% substance, 10.0% enzyme to substance, pH10.0, 45℃ and 8h. In such condition, the degree of hydrolysis was 33.5%, peptides content was 2:86g/100mL, ammoniac nitrogen content was102.94mg/100mL, the Mr ranges of hydrolysates above 5,000, from 2000 to 5,000, from 200 to 2000 and below 200 were 21.5%, 24.4%, 51.9% and 2.2% respectively. The optimum parameters for the second enzymatic hydrolysis by papain indicated 2.0% papain to substance, pH 7.0, 60℃ and 4h. Peptides and ammoniac nitrogen were 2.1g/100mL, 230mg/100mL respectively, the Mr ranges above 5,000, from 2,000 to 5,000, from 200 to 2,000 and below 200 were 10.6%, 16.6%, 67.1%, 3.7% respectively.4. The research of high Fischer ratio oligopeptides isolating and debittering indicated: The Mr 5,000 withholded ultrafiltration was used to remove peptides and proteins. Mr ranges of hydrolysats passed through the membrane above 5,000, from 2,000 to 5,000, from 200 to 2,000 and below 200 were 6.4%, 12.2%, 76.9%, 4.5% respectively. It attained the demand of oligopeptides. In order to promote Fischer ratio, powdered activated carbon was studied as AAA adsorbent. The optimum parameters were adsorbent to the volume of hydrolysates 1:3, pH3.0, 20C and 3h. The product had 2.7g/L nitrogen content, Fischer ratio was 22.59, Mr ranges below 5,000 and below 2,000 were 94.6% and 70.5% respectively. The yield was 34.1% on protein of CGM by weight. The bitter weakened by the means of hiding bitter peptides in this research.5. The quantity standard was formulated according to the preliminary study on preparation of high Fischer ratio oligopeptides by two enzymes method from CGM. It could keep the quantity on sensory organ level, physical and chemical level and microorganism level in production controlling.Preparation high Fischer ratio oligopeptides by enzymatic hydrolysis belonged to protein engineering and enzyme engineering of biology techn...
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