Optimization Of Probiotic Fed-batch Culture Processes And Study On Online Monitoring Of Viable Biomass

Probiotics are now mainly produced by batch fermentation which have been widely used ithe field of food, medicine and others, but both of viable cells density and production effici-ency is still low. In this parper, the fed-batch fermentation processes and viable biomass onli-ne monitoring of three kind of probiotic Bifidobacterium longum, Lactobacillus acidophilus and Streptococcus faecalis were investigated.The effect of different nitrogen concentrations on the growth of Bifidobacterium longum was investigated. The results showed that the optimum nitrogen concentration was skim milk powder50g/L and yeast extract lOg/L, the viable cell density was3.2×1010cfu/mL, which was33.33%higher than that of original process.For Lactobacillus acidophilus, the seed age and lactose feeding strategies were inverstig-ated. It was found that the optimum inoculum age was5.5±0.5h and cell growths under the two lactose feeding strategies were almost same, which laid a foundation for its industrial preparation and scal-up.The effect of pH, dissolved oxygen and glucose feeding strategy on the cell growth of Streptococcus faecalis was also studied. The results showed that the optimal pH of Streptoco-ccus faecalis YIT007cell growth was7.2. Dissolved oxygen had effects on its cell growth and organic acids generation, the oxygen demand in different growth stages were different. According to this, we proposed step control dissolved oxygen, useing exhaust carbon dioxid to adjust the amount of air flow rate to control the dissolved oxygen in fermentation broth at different levels. Using dissolved oxygen feedback to control the glucose feeding rate could improve the productivity significantly. The dry cell weight reached7g/L under the optimum culture condition, which was64.29%higher than that with initial condition, and the maxmam specific growth rate was1.3h-1.In order to know the changes of biomass in culture process, we studied online monitorin-g of viable biomass using viable cell-base biosensor. The results indicated that ABER viable-cell mass monitor could describe the cell growth of Bifidobacterium longum and Lactobacillus acidophilus, the correlation coefficient was0.99, and therefore the probe can be used in the fermentor directly.However, it was more fluctuated and interfered by ventilation and agitation when used in Streptococcus faecalis. According to this result, we developed a kind of device to put the fermentation broth in it and the problem was well solved.The results of this study, provides a basis for the industrial application of probiotics.