Study On The Microbial Synthesis, Purification, Nature And Application Of γ-Poly Glutamic Acid

γ-poly glutamic acid (γ-PGA) which was produced outside the butcher by the minority bacterium could be used as the biodegradable biological compatible material and the water-soluble high polymer material,and it has the promising application in the environment improvement, the medicine,food,the chemical industry,the agriculture and the cosmetics domain, with the developed country using the biodegradable high polymer more and more, adding the global attention to the environment,people gradually take the synthesis ofγ-PGA seriously and expand its many new application area.So completely,systematically and largely building microbial production methods ofγ-PGA and researching and developing production technology ofγ-PGA have positive practical significance.γ-PGA was prepared by Bacillus subtilis via fermentation.At first,γ-poly-glutamic acid liquid shaker fermentation was used to obtain the greatest yield ofγ-PGA,followed by improving product separation and purification process,and the nature and the application ofγ-PGA were studied.The results showed:1 single-factor optimization of fermentation media and culture conditions were carried out.From these results,the medium composition which was able to get a larger output ofγ-PGA contained:L-glutamate 2%,peptone 0.6%,corn saccharification liquid 6%,NaCl1%; the suitable fermentation conditions were as follows:Flask content 50ml/250ml,pH7.0,temperatuer 37℃,rotation speed 150rpm,and fermentation time 48h.2 The extraction and purification ofγ-PGA:a high viscosity fermentation broth was got by microbial fermentation,then organic solvent was used to precipitation and obtainγ-PGA.The best extracted method was ethanol extraction.The concentration was 100%,the addition was 2.5 times.3 Product identification:degradation products identified by thin-layer chromatography to prove that degradation products were only the glutamic acid, and the product was detected by IR and UV,and we could see that the polymer was polyamide.4 Physical and chemical properties ofγ-PGA:the effect of temperature on the viscosity ofγ-PGA was studied to prove that viscosity ofγ-PGA decreased with temperature increasing;pH had an effect on the viscosity ofγ-PGA,andγ-PGA had maximum viscosity at pH=6;the concentration ofγ-PGA had an effect on the viscosity ofγ-PGA,the viscosity increased with the concentration increasing;the effect of metal ions on the viscosity ofγ-PGA was studied to find that the viscosity decreased with adding metal ions and different ionic had little difference about effect on the viscosity ofγ-PGA;the isoelectric point ofγ-PGA had been determined with the biuret method,we could see that the isoelectric point was 2.22;The molecular weight ofγ-PGA was 960kDa determined by GPC;influence of y-PGA drying method on outward appearance and receiving rate of product was studied,no matter outward appearance or receiving rate,we could find that the freezing drying method was best method to obtain the product;y-PGA had the water-retaining property truly,and the water-retaining property increased with the concentration increasing,and the hygroscopicity of y-PGA would increase if it underwent the ultraviolet illumination.y-PGA could have the red purple color in the strong alkaline solution with the cupric sulfate;the solution of y-PGA was joined with yin triketone solution then we could see lamination,and the lamination place had bright yellow belt;the solution of y-PGA was joined with the saturated cupric sulfate solutions to produce the blue color complex compound,after the vibration,but the complex compound did not vanish. These phenomena was the same as the protein.The purified y-PGA had two main peak in the high performance liquid chromatogram,and out of peak hours were respectively 1.722min and 2.728min,when peak areas were 90.35% and 3.96%.5 The application of y-PGA:high absorbent resin was preparated by y-PGA and styrene as raw material,aluminum hydroxide as the cross-linking agent,azo-bis-isobutyronitrile as initiator,and researched factors such as the amount of crosslinker,initiator solution usage and pH value to confirm whether the resin absorbent could be affected by them or not.The results showed that the best preparation process was as follows temperature 80℃,γ-PGA and styrene mass ratio of 3:1,initiator dosage 1.5% of the total mass,the amount of cross-linking agent 1% of the total mass,solution pH value 6.In addition,y-PGA had a certain effect on the sewage treatment.