Studies On High Cell Density Culture And Technology Of Lactobacillus Acidophilus

This thesis is mainly about the high cell density cultivation of Lactobacillus acidophilus, including the optimization of the medium and culture conditions, and the amplifying of fermentation technique was implemented in 8L agitating ferment vat. The aim of this study was to provide some theoretical and practice guidance, from these studies, we can make conclusions as following:The influence of the carbon sources, nitrogen sources and multiplication factors on the growth of Lactobacillus acidophilus was discussed to optimize the composition of the proliferation medium for Lactobacillus acidophilus. By single-factor tests and synergic-effect tests, the optimum composition of the media were determined as following: the carbon sources: glucose: Lactose = 3:1, 4%; the nitrogen sources: de-fatted milk powder, 5% and yeast extract, 0.8% ;multiplication factors:extract fluid from pig liver, 40%. By optimization, the viable bacterial count of Lactobacillus acidophilus could reach 1.0×109 CFU/mL.Culture conditions and processes were researched on the basis of optimization of proliferation medium, and this research mainly included neutralization test for constant pH and fed-batch. The study showed that the optimum culture conditions and processes were determined as following: inoculation amount was 1×106 CFU/mL, cultivate temperature was 37℃, initiative pH was 5.70, medium added in 16h, incubating time was 21h, the amount of medium added was 25%, and the cultivate pH was controlled between 5.50~5.70 by adding 25% (w/w) NH4OH during the cultivation. The maximum viable bacterial count of Lactobacillus acidophilus could reach 1.0×1010 CFU/mL at the end of culture.A pilot-scale experiment was carried out on the basis of hell cell density culture of Lactobacillus acidophilus at the laboratory level, to do some research on the feeding time, incubating time and the number of viable bacteria. The results showed that in the course of experiment, medium added in 8.5h, incubating time was 9.5h, and the viable bacterial count of Lactobacillus acidophilus freeze-dryed could reach 7.2×1010 CFU/g.