Production Of ACE-inhibitory Peptides By Lactobacillus Casei D400

ACE inhibitory peptide has a function on lowering blood pressure. Enzymatic or microbial fermentation is the primary means of obtaining ACE inhibitory peptides from milk. Lactobacillus casei belong to the same type fermentation of lactic acid bacteria, has good acid production activity and protein hydrolysis activity, widely used in the various of dairy products. This paper studies screening and identification of the Lactobacillus casei, the determination of proteolytic activity of the strain, ACE inhibitory activity of the strain and contents of amino acids in fermentation milk whey and other aspects, which establishes screening model of Lactobacillus casei with ACE inhibitory activity. Major findings are as follows:1. After 4 hours digestion by the artificial gastric juice( pH = 2.5), the viable rate of D400 and Y5-2b can reach 89.09% and 86.28%, and the viable rate of digestion is still 96% to 98% after the artificial intestinal juice and 0.3% concentration bile salt. Therefore, D400 and Y5-2b have good resistance to gastrointestinal environmental performance. Further more, D400 in terms of the growth state in the milk, acid production or proteolytic activity areas were higher than Y5-2b, ACE inhibitory activity of D400 fermented milk was higher than Y5-2b. therefore, selected L.casei D400 as the experimental strains. Based on experiment data of physiological, biochemical and 16S rRNA gene sequence, determins D400 and Y5-2b as Lactobacillus casei.2. With the cell biomass and titratable acidity of L.casei D400 fermented milk increased, the proteolytic activity and the ACE inhibition rate rised, which indicated with the growth of cell biomass, ACE inhibitory peptide included in the milk protein gradually released, proteolytic activity and ACE inhibition has significant correlation.3. Single factor test showed that the fermentation temperature, fermentation time and the concentration of non-fat milk solids will affect the proteolytic activity and the efficiency of ACE inhibition of the strain. Optimized L.casei D400 in milk fermentation conditions are: SNF concentration of 10%, fermentation time 24 h, fermentation temperature 37°C. In such conditions, ACE inhibition rate of L. casei D400 is 81.15%.4. After the digestion of pepsin and trypsin, ACE inhibition rate of L.casei D400 decreased from 81.15% before to 67.83%, indicating ACE inhibitory peptides produced by L.casei D400 has a certain tolerance to the gastrointestinal tract protease digestion. 5. The amino acids content in the L.casei D400 fermented milk analysis show that the hydrophobic amino acids in the proportion of the total amino acids increased from the fermentation before 22.29% to 48.50%, proline proportion in the total amino acid has increased significantly from 1.67% before to 18.75%, and the relative increase contents was higher than other amino acids. Leucine and threonine content were relatively large increase, isoleucine, arginine, lysine, valine followed, and found methionine and phenylalanine. Combination structure of ACE inhibitory peptide sequence which has known, the conditions of producing ACE inhibitory peptides formed. Therefore, the capacity of L.casei D400 produce ACE inhibitory peptides is because of its hydrolyzed protein activity producing proline, other hydrophobic amino acids and aromatic amino acid.