Study On Hydrolyzing Conditions Of Casein By Lactobacillus Bulgaricus And The Hydrolysate Analysis

Casein is the main protein in natural milk, it as a carrier of minerals promote the absorption of the body and have the effect of prevention related diseases, At the same time casein hydrolysis to produce some peptides with biological activities.Lactobacillus bulgaria is a common one of the major components of dairy starter cultures. In the process of fermentation cannot satisfy microorganisms need to grow, but Lactobacillus bulgaria can be generated by hydrolysis of casein small molecular peptides and amino acids for material synthesis and physiological activities in hydrolysis of casein in fermented dairy products at the same time affecting the flavor of fermented milk curd and formation.Casein hydrolysis is the first step of protein utilization of lactic acid bacteria in Fermented milk. Lactic acid bacteria generate small molecular peptides and amino acids by hydrolysis of casein proteolytic system, to enter the body through the internal related transport system, which was further hydrolyzed.This experiment mainly Lactobacillus bulgaria ATCC 11842 as the research object in Lactobacillus bulgaria KLDS 08007, KLDS 08009, KLDS 08010, KLDS 08014 and KLDS 08009 as control study. Through the fermentation of casein medium experiment to determine the best hydrolysis conditions, and the hydrolysate and related enzyme activity were studied.The result of the research are as follows:(1)By single factor experiment and response surface experiments to determine the optimum hydrolysis conditions of casein hydrolysis of lactobacillus bulgaria and culture conditions: p H 6.78, protein concentration was 0.97%(w/v), the inoculation amount was 109CFU/m L, 6.24%(v/v), 37 ℃fermentation 48 hours for the degree of hydrolysis can reach 13.9115%.(2)Under the best conditions of six strains Lactobacillus bulgaria ATCC 11842, KLDS 08007, KLDS 08009, KLDS 08010, KLDS 08014 and KLDS 08018 fermentation for 48 hours, determination of different strains fermented liquid of casein hydrolysis and peptide content,by comparing the found strain ATCC 11842 strongest hydrolysis ability, degree of hydrolysis was 13.89%, peptide content was 0.63 mg/m L. Determination of six strains of CEPs activity and ability to comparative analysis found that the hydrolysis of the enzyme activity and strain ability was correlation, lactobacillus bulgaria ATCC 11842 hydrolysis ability was stronger, the enzyme activity also was stronger, specific enzyme activity was 6.73U/mg.(3)SDS-PAGE analysis of casein hydrolysate of lactobacillus bulgaria ATCC 11842, through the map found gradually with the extension of fermentation time casein hydrolysis and produce different sizes of peptides.Through LC-MS analysis of hydrolysate, casein hydrolysis to produce 77 kinds of 6~25 peptide fragments, which accounted for 77% kinds of polypeptide 8~14 peptides.This experiment the contents of the above studies show that strains of hydrolysis ability was related to its activity of CEPs, The activity of enzyme is the stronger hydrolysis ability was strong.Hydrolysis of casein is mainly CEPs degradation and generate small molecular peptides and amino acids.