| The Lactobacillus paracasei HD1.7 which was obtained by our lab could produce bacterocin, which had wide antimicrobial spectrum. The process of Lactobacillus paracasei HD1.7 fermentation was optimized in the paper, and its fermentation kinetic model was established, which could provided a theoretical basis for further study and industrial production.Inoculating fermentation conditions of the Lactobacillus paracasei HD1.7 are studied. The suitable age of the seed was determined to be 14h and the inoculation quantity was 6%. On the basis of single-factor test, the composition of the basic broth was determined: yeast 1%, peptone 1%, beef extract 0.5%, glucose 2%, Tween80 0.3%, K2HPO4 0.2% NaCl 0.3%, MgSO4 0.02%, MnSO4 0.003%. Based on this,Plackett-Burman design was used to evaluate the influences of all related factors in fermentation medium. The results showed that yeast powder, glucose and beef extract were the main affecting factors while the other additives had no significant effects on fermentation of Lactobacillus paracasei HD1.7. Then the optimum fermentation medium was determined according to CCD (Central composit Design) and Response Surface Analysis with SAS software. The optimal fermentation medium for Lactobacillus paracasei HD1.7 was: glucose1.5%, beef extract 0.62%, yeast extract 0.71%, peptone1%, Tween80 0.3%, K2HPO4 0.2% NaCl 0.3%, MgSO4 0.02%, MnSO4 0.003%. Under this fermentation medium condition, the activity of Lactobacillus paracasei HD1.7 fermentation was 389AU/mL.Fermentation was further conducted in 10L fermentation tank. The influence of pH and temperature on fermentation was studied. By analyzing kinetic parameters, the control methods were obtained respectively. pH control method of fermentation process was 0 15h keep pH 6.0 at first and then adjust pH to 3.5 till the end of fermentation. When fermentation experiment was conducted by using the optimized controlling method, the antimicrobial activity was 1100.2AU /mL in 42h. Temperature control method was temperature control at 37℃during 0 21h, then reduce the temperature to 33℃till the end of the fermentation. With this control method of fermentation, production quantity had increased. The antimicrobial activity increased to 1444.4AU /mL in 42h.Based on the optimized methods, fermentation (pH and temperature) experiment is carried out in 10L fermentation tank. Kinetic models are proved and developed with the biomass, glucose concentration and antimicrobial activity of Lactobacillus paracasei HD1.7.Dynamic model of cell growth:Dynamic model of production formation:Dynamic model of substrate consumption:By the verifiction of model, the results showed that the dynamci model could efectively reflect the fermentation process of Lactobacillus paracasei HD1.7. |
