The Application Of Whey Protein Hydrolysates In Lactic Bacteria Culture

In this study, whey protein powder (WPC80) was used as raw material. On the basis of giving respective hydrolysis condition of alcalase and flavourzyme, with the hydrolysis degree as index, the hydrolysis technological process of protamex was optimized by orthogonal experiments. The physical and chemical properties of the product were determined and the application of whey protein hydrolysates (WPH) in lactic acid bacteria culture was discussed. The main conclusions are as follows:1Alcalase and flavourzyme were combined to hydrolysis whey protein. The results substantially increased compared with earlier data of single protease concluded from the project group. The average speed and DH of synchronous hydrolysis were both greater than step hydrolysis. The optimal technological hydrolysis process was determined:4h, pH9,55℃, E/S1:20, E1:E24:6. In such a condition, the degree of hydrolysis could reach64.3%. All physical and chemical index of the production were accord with the demands. The WPH were suitable for providing nitrogen source for microorganisms.2Lactobacillus bulgaricus was chosen to be tested strain. According to the result of determing growth curve, the result of replacing peptone with WPH was much better than commercial MRS. The optimal amount to replace was8g/L3It was effective that WPH replaced peptone and beef extract powder in MRS respectively to cultivate Lactobacillus bulgaricus、Streptococcus thermophilus、 Lactobacillus planetarium、Lactobacillus casei、Bifidbacteria. The amout of growth and growth trend reached the level of commercial MRS. However, it was effective for all tested strain except Lactobacillus bulgaricus. The growth of Lactobacillus bulgaricus was much lower than commercial MRS、4For Lactobacillus bulgaricus、Streptococcus thermophilus、Lactobacillus planetarium、Lactobacillus casei、Bifidbacteria, replacing peptone and any other nitrogen source simultaneously with WPH(double substitution) made bacteria growth close to even better than commercial MRS medium and the self-made MRS medium. Of five kinds of lactobacillus, the double substitution had better effect on Streptococcus thermophilus and Bifidbacteria. 5Replacing all kinds of nitrogen sources simultaneously with WPH(Complete substitution) led to that the growth quantity of Lactobacillus bulgaricus was so low that the exponential growth phase lasted only lh and the maximum absorption value was just0.19. For Streptococcus thermophilus、Lactobacillus planetarium、Lactobacillus casei and Bifidbacteria, complete replacement made bacteria growth close to or better than commercial MRS medium and the self-made MRS medium. Of five kinds of lactobacillus, the complete substitution worked best for Bifidbacteria.