Study On Inhibitory Factors And Kinetics Of Metabolite Inhibition In Bifidobacterium Growth

The research described in this dissertation focuses on the inhibitory effect of factors on the growth and fermentation of Bifidobacterium and the kinetics model of metabolite inhibition in the growth of Bifidobacterium.The effects of the composition of meidium on the growth of Bifidobacterium were investigated. The results showed that the medium including glucose, trypeptone, and yeast respectively higher than 4 mg/mL,4mg/mL,3mg/mL was not a primary limiting factor. Although the biomass was increased 2.1 times under controlled-pH than uncontrolled, the product accumulation 0.28 mmol /ml caused feedback inhibition on the growth of Bifidobacterium leading to an uncoupling of biomass formation. The growth of Bifidobacterium was inhibited completely when 0.17 mmol /mL lactate and 0.17 mmol /mL acetate was added to the culture medium. The effect of acetate and lactate to Bifidobacterium were investigated. The results showed that the growth of Bifidobacterium was inhibited in the medium added respectively with 0.44 mmol /mL acetate and 0.28 mmol /mL lactate. With high concentration of acid (higher 0.22 mmol /mL), the order of different molar ratio acetate:lactate, from big to small, is 1:1>3:2>3:1, and with low concentration of acid (lower 0.22 mmol /mL) the order of that is 3:2>1:1>3:1. The mechanism of effect of weak organic acid to Bifidobacterium were investigated in primary, the results showed weak organic acid not only reduced the rate of drop of pH, but also inhibited the growth of Bifidobacterium.On the basis of the relation between different concentration of production and the specific growth rate μ and existing model, the kinetic model of Bifidobacterium inhibition of metabolite wasμi/μ0=K1[1-(P1/Pm1)α1]+K2[1-(P2/Pm2)α2].With help of Matlab6.5, kinds of kinetic parameter are estimate, and the kinetic model of acetate and lactate inhibition in the growth of Bifidobacterium is μ= 0.176[-0.60723 (1-(P1/38.41) 3.0908)+1.73246(1-(P2/25.64) 1.1724)]. Taking into account the influence of H+ on Pm, Pm'(A)= 1.3333X3-30.5714X2 +228.9524X -522.8, Pm'(L)=3.3333 X3-60.1429X2+366.2381X-730.0.Comparing with value of experiment, it was approved that the kinetic model was very closely to the growth of F-35, but the model of F-35 was not completely appropriate to other kinds of Bifidobacterium such as Bifidobacterium longum.