High Cell Density Culture Of Lactobacillus Rhamnosus NCU239

Lactobacillus rhamnosus is very benifica to human body. This paper had studied following contents to achieve Lactobacillus rhamnosus NCU239 high desity culture.(1) The study of fermentation medium MRS-A. MRS culture medium was used as the basic medium for optimizing the fermented condition of Lactobacillus. rhamnosus. Using single factor test and Box-Behnken design, we finally got the improved MRS-A medium:4%glucose,1.2%peptone,4.8%corn steep liquor, with other components remaining the same as MRS medium. With 3% inoculation,18h culture at 37℃,the viable cell number could reach 2.56x109cfu/mL and 1.65-fold live bacteria counts in MRS-based culture medium, showing no difference with predicted value 2.68×109cfu/mL.(2) The study of fermentation medium MRS-B.MRS culture medium was used as the basic medium for optimizing the fermented condition of Lactobacillus. rhamnosus. Using Plackett-Burman design, Steepest ascent path and the Central Composite Design, we finally got the improved MRS-B medium:beef extract 2.6%, tween-80 0.3%, peptone 2%, diammonium citrate 0.4%, with other components remaining the same as MRS medium. With 3% inoculation,18h culture at 37℃,the viable cell number could reach 3.54×109cfu/mL and 2.19-fold live bacteria counts in MRS-based culture medium, showing no difference with predicted value 3.68×109cfu/mL.(3) The study of fermentation condition and cultivation strategy. Using the MRS-B medium as fermentation medium, we had investigated the fermentation temperature, the fermentation pH, the inoculation and the agitation rate. Then we had studied batch fermentation, batch fermentation with chemical neutralization and fed-batch fermentation with chemical neutralization. The results show that the most viable cell number can reach 6.92×109cfu/mL in the fed-batch fermentation with chemical neutralization.