Study On The Separation And Purification Of Poly (Glutamic Acid) And Application

γ-PGA is a biomedical material with many many excellent properties.γ-PGA with different molecular weight in the fermentation broth of γ-PGA was separated and extracted by membrane separation.High molecular weight γ-PGA was used as water-retaining and sand-fixation material to study its water-retaining and sand-fixation properties.The low molecular polyglutamic acid was used in the preparation of nano-materials and the preparation process was optimized.Firstly,using γ-PGA purity as the index,the optimum conditions for extracting γ-PGA by 10 kDa ultrafiltration membrane were obtained as follows:inlet pressure 0.4 Mpa,solution temperature 31℃,γ-PG A concentration 9.7 g/L,water elution times 7 times.The lowest purity of trapped fluid was 88%and average molecular weight of trapped fluid was 1×106 Da.Secondly,with the removal rate of glutamic acid as the index,the optimum conditions for extracting γ-PGA with low molecular weight of 5 kDa ultrafiltration membrane were obtained by single factor and orthogonal experiment.The optimum conditions were as follows:dilution factor 3 times,inlet pressure 0.5 Mpa,solution temperature 30℃.elution times 4 times,the ion removal rate was taken as the index,and the optimum conditions of nanofiltration were obtained by single factor and orthogonal experiment.The optimum conditions of nanofiltration were as follows:inlet pressure 0.8 Mpa,solution temperature 50℃,and the average molecular weight of the elution was 1×105 Da.The molecular weight of the permeate was 1000 Da-3000 Da,the molecular weight was 2000 Da.Then,using the absorbent ratio as an indicator,The optimum conditions for preparation of γ-PGA/CS gel by single factor and orthogonal experiment were obtained as follows:total volume of reaction system 60 mL,γ-polyglutamic acid 0.6 g,chitosan 2.4 g,acetic acid 0.4 mol·L-1,acetic acid 20 mL.The ratio was 50.89±0.23.After 8 d,the addition of γ-PGA/CS water-retaining agent was 0.1%.After using γ-PGA/CS water-retaining agent,the cumulative evaporation rate in soil decreased by 23%,the wind erosion modulus decreased from 35.6 g·m-2·min-1 to 27.3 g·m-2·min-1 and the thickness of solidified layer was 1.5cm.Compared with the blank sample,the aggregate content of>0.25mm in soil particles increased by 13.7%after using γ-PGA/CS water-retaining agent.Finally,with the average particle size as the index,through Plackett-Burman experiment and response surface optimization,three factors which have significant influence on the particle size of γ-PGA/CS nanomaterials are obtained,which are the amount of CaCl2,the concentration of γ-PGA and the concentration of CS in the preparation of γ-PGA/CS nanomaterials.The optimum preparation conditions were as follows:the amount of CaCl2 1 1 mL,the concentration of γ-PGA 1 g/L,the concentration of CS 0.9 g/L,and the particle size of nano-materials was 126.10 ±0.13 nm.Be used for the preparation of calcium nutrition fortifier,γ-PGA and Ca2+ reaction rate increased with the increasing of Ca2+ concentration and,when the mole ratio of 1:2,combining rate is close to a 1-0.54,and temperature on the binding reaction.