Biosynthesis And Nanocapsule Preparation Of γ-Polyglutamic Acid

γ-Polyglutamic acid(γ-PGA) is a biodegradation, water solubility, non-toxicity,edibility biopolymeric product. In order to reduce γ-PGA production cost, itsbiosynthesis and extraction were studied; in order to widen the application field of it, weresearched its application in sustained-release carrier.1. γ-PGA was included in the fermentation fluid which was produced by Bacillussubtilis. Isopropanol was the precipitating agent which was used to extract the productfrom the fermentation fluid. A Box-Behnken design was used to evaluate the extractioneffects of the three related factors. The optimal isopropanol addition was4.5times ofthe zymotic fluid volumes, the optimal sedimentation temperature was-5℃, and theoptimal sedimentation time was23h. Under the optimum condition, the production ofγ-PGA was17.96g/L, the precision of prediction run up to99%. Thin layerchromatograph and infrared spectroscopy were used to identify the structure of γ-PGA;the purity with95%was measured by HPLC.2. The preparation of novel biodegradable and edible nanocapsule based onself-assembly of γ-PGA and Chitosan (CS) under normal temperature and pressure wasdescribed in this part. After the Plackett-Burman design by Design-Expert7.0, it wasfound that the average particle size (Z-Ave) and polydispersity index (PDI) ofnanocapsule measured by Malvern zetasizer Nano-ZS instrument depends on the massconcentration of γ-PGA, volume of γ-PGA and pH value of CS. A Box-Behnken designwas used to optimization the γ-PGA/CS nanocapsule preparation conditions, and thenthe best experimental conditions was obtained as follows: pH value of CS was4.0;volume of γ-PGA was18m; mass concentration of γ-PGA was.1g/L. The Z-Ave andPDI of the nanocapsules prepared under the best contidions were175nm and0.15,respectively.3. The preparation of nanocapsule was based on self-assembly of γ-PGA and CS,using nifedipine (NF) as a model drug. When2mL of nifedipine solution with theconcentration of0.5g/L was added to prepare nanocapsule, the Z-Ave and PDI would be250nm and0.202, respectively; what’s more, the drug loading and encapsulationefficiency were59.72%and12.44%. Sustained-release performance measurementsshowed that there was obvious sustained release effect of the nanocapsule in simulatedintestinal fluid, while almost no sustained release effect in simulated gastric fluid. Andthe cumulative release of drug could be well fitted Higuchi equation(Mt/M∞=0.1601t1/2+0.0486, R2=0.973) and Peppas equation (Mt/M∞=0.2043t0.4376,R2=0.9816).4. The preparation of nanocapsule based on self-assembly of γ-PGA and CS using jasmine essence as a model. With10%of Teewen-80,2%of essence and0.5mL ethanol,the Z-Ave, PDI and zeta-potential were153nm,0.208and35.2Mv, respectively.Andthen the Electronic Nose was used to measure the delayed release properties of thenanocapsules. The experiment results showed that the nanocapsule carried jasmineessence had slow release capability at room temperature and it could be used in essencerelease.To sum, at low temperatures taking the precipitating agent with isopropanol toextract γ-PGA from the fermentation fluid was a practical, effective and completely newmethod; nanocapsule prepared by self-assembly of γ-PGA and CS at normaltemperature and pressure can be used as drug carrier and essence carrier.