| Hyaluronic acid is a high molecular mucopolysaccharide, because of its special physiological action, extraordinary rheology character and moister-holding function, it is widely applied for health food, cosmetic industry and medical domain. The objective of this study is to explore the HA production by microbiology fermentation ,the rheology properties of HA and application of HA. The main results are as follows:1. The fermentation medium and condition of culture for the strain mutagenized were firstly optimized. On the basis of the single factor experiment, the carbon, nitrogen sources and inorganic salts were determined, and then the mathematical model was established by the quadratic rotary combination design. The optimum concentrations of culture medium were determined as 3.00 g/100mL yeast extract, 2.00 g/100mL peptone, 0.50 g/100mL glucose, 0.15 g/mL MgSO4. The conditions of fermentation were optimized by orthogonal test. The proper temperature, pH, rotating speed and medium volume in 250mL shake flask were 37℃, 7.8, 200 r/min, and 30 mL, the HA yield got 224.52 mg/L.2. The effects of concentration of glucose, pH, temperature and rotating speed on HA production by fermentation in 5L fermentor were investigated, and the dynamical model of HA in batch fermentation was established. The optimum conditions were as follows: concentration of glucose 30 g/L, temperature 35℃, rotating speed 200 r/min, pH 7.0, under the conditions, the yield of HA got 1.92 g/L. On the basis of optimium conditions, biomass and HA yield were simulated by Slogistic, Logistic and SGompertz model. The results showed that the Logistic model was suitted to the simulation of biomass, the simulation equation was as follows: y = 2. 933?1 +(x/21.18.41985)4.453, the correlation coefficient touched 0.999; the Slogistic model was fit for HA synthesis, the simulation equation was as follows: 10.318(13.413), the correlation coeffcient touched 0.996; the DoseResp model was suitted to gulcose consumption, the simulation equation was as follows: y = 2 .085+1 +12060..5156X6?2.80, the correlation coeffcient was 0.991.3.The optimal conditions to separate HA from fermentation broth were discussed in this chapter.The effect of HA concentration in broth, the addition of CTAB, precipitation temperature and time, NaCl concentration and alcohol concentration on the HA yield and protein impurity content were investigated. The optimum condition for purification were HA concentration 0.8 g/L in broth, the precipitation temperature 35℃, time 2 h, and NaCl concentration 1.5 mol/L, alcohol concentration 70%. Under the conditions, the HA yield got 96.62%, the protein content of HA 1.51%, the removed amount of protein in HA was 86.09%.4. The rheological properties and viscoelasticity of hyaluronic acid and some main influence factors on them were explored in this paper. The materials used in this paper were hyaluronic acid with different molecular weight and hyaluronic acid samples produced by fermentation in our laboratory. By using rheometer and fitting Newton Power Law equation, the effects of concentration, molecular weight, temperature and pH on rheological properties and viscoelasticity of hyaluronic acid solution were studied. The results showed that, with the increase of shear rate, viscosity of hyaluronic acid solution gradually reduced, which proved that hyaluronic acid belonged to a typical shear-thinning non-Newtonian fluid. With the increase of solution concentration, the fluid shear-thinning behavior was enhanced. It presented a positive correlation between viscosity of hyaluronic acid solution and molecular weight of HA, while a negative correlation between viscosity and temperature of solution. Under the same concentration of HA solution, the flow index of Newton Power Law equation gradually reduced with the increased molecular weight of HA. With the increased molecular weight and concentration of hyaluronic acid, the elastic modulus of liquid was enhanced while viscous modulus of liquid was reduced.5. The effect of the addition of HA and CMC on the flow behavior of milk systems were studied. Use the rheometer to test the rheological property of milk with HA added, with the increase of HA addition, the viscosity of milk gradually increased, the trend was similar with CMC added. We determined the thixotropy property of milk with HA or CMC added, when the addition of HA was 0.1%, the viscosity of milk varied little at the range of the shear rate, showed a Newtonian-type fluid. whereas when the addition of HA was 0.2%, the viscosity of milk gradually decreased at the range of the shear rate, show pseudoplastic and the shear-thinning fluid, which is different to the milk without addition HA or CMC. |
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