| y-Polyglutamic acid(y-PGA) is a water soluble, biodegradable, non-toxic, edible high polymer material. It has been applied in fields of food, medicine and cosmetic. In order to improve the per unit output and reduce the cost of production of y-polyglutamic acid, its fermentation process was researched; in order to broaden the application fields of y-polyglutamic acid, its application in sustained-release carrier was researched.y-PGA was included in the fermentation fluid which was produced by Bacillus subtilis. Ethanol was the precipitating agent which was used to extract the product from the fermentation fluid. The single factor experiment and Box-Behnken experiment was used to optimize the composition of medium and conditions of fermentation. The optimal sucrose addition was44.9g/L, the optimal nitrogen addition was7.1g/L, the optimal sodium glutamate addition was51.1g/L, the optimal K2HPO4addition was1.8g/L, the optimal MgSO4addition was0.3g/L, the optimal pH was7.5. And the optimal fermentation time was24.5h, the optimal revolving speed of table concentrator was240r/min, the optimal inoculum size was5.9%, the optimal fermentation temperature was40℃. Under the optimum condition, the production of y-PGA was41.6g/L, it was improved32.9%than primary medium.The preparation of novel biodegradable and edible nanoparticle based on self-assembly of y-PGA and geltin under normal temperature and pressure was described in this part. After the Plackett-Burman design by Design-Expert7.0, it was found that the average particle size and Zeta-potential of nanoparticle measured by Malvern zetasizer Nano-ZS instrument depends on the mass concentration of y-PGA, concentration of geltin and pH value of gletin. A Box-Behnken design was used to optimization the y-PGA/geltin nanoparticle preparation conditions, and then the best experimental conditions was obtained as follows:the mass concentration of y-PGA was0.7g/L, the concentration of geltin was0.5g/L, pH value of geltin was3.0. The Z-Ave and Zeta-potential of the nanocapsules prepared under the best contidions were189.2nm and36.3mV, respectively.The preparation of nanoparticle was based on self-assembly of y-PGA and geltin, using rifampin as a model drug. When the concentration of rifampin was0.15g/L and the addition of ethanol was5g, the Z-Ave, intensity, Zeta-potential and PDI would be335.8nm,98.2%,13.7mV and0.237, respectively. What’s more, the drug loading and encapsulation efficiency were51.5%and17.2%. Sustained-release performance measurements showed that there was obvious sustained release effect of the nanoparticle in simulated intestinal fluid, while almost no sustained release effect in simulated gastric fluid. And the cumulative release of drug could be well fitted Higuchi equation (Mt/M24=0.0409t1/2+0.1005, R2=0.9785) and Peppas equation (Mt/M24=0.075t0.8664, R2=0.9892).The preparation of nanoparticle based on self-assembly of y-PGA and geltin using sweet-scented osmanthus essence as a model. With0.15g of Teewen-80,0.15g/L of essence,30min of emulsification time and400r/min of stirring speed, the Z-Ave, intensity, PDI and zeta-potential were378.6nm,93.4%,0.273and16.8mV, respectively.And then the Electronic Nose was used to measure the delayed release properties of the nanoparticle. The experiment results showed that the nanocapsule carried sweet-scented osmanthus essence had slow release capability at room temperature and it could be used in essence release.To sum, the response surface method was appropriate to improve the output of y-PGA. The nanoparticle prepared by self-assembly of y-PGA and geltin at normal temperature and pressure can be used as drug carrier and essence carrier. |
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