| Poly y-glutamic acid,or y-PGA for short,is a kind of water soluble amide compounds.It can be produced by a variation of bacillus.The anionic material is a polyamide,polyamide is generated after the formation of peptide bond by a amino and y carboxyl of L-Glutamic acid or between D-Glutamic acid monomer.y-PGA has special physicochemical properties and biological characteristics,such as good film reforming property,fibre forming property,oxygen resistance activity,plasticity,binding property,moisturizing performance,and biodegradability etc.It is also a new type of polymer biological material whith non-toxicaction to human body and environment.So it can be used widely in food,cosmetics,medicine,agriculture,industry,oil dehydration,environmental protection,water treatment,coating,daily necessities.The culture medium of prouducing y-PGA was optimized by one factor test,design of PB,steepest ascent path and response surface method.The optimum medium composition was:7.00g/L ammonium C,100.00g/L corn saccharification liquid,6.00g/L NaCl,5.00g/L KH2PO4,0.08g/L MnSO4,40.00g/L monosodium glutamate,0.42g/L CaCl2 and 1.25g/L MgSO4.Under the optimal culture conditions,the production of y-PGA was 73.40g/L.The production of y-PGA was further improved by fed-batch fermentation of corn saccharification liquid,ammonium C and monosodium glutamate.And eventually the yield of y-PGA could be up to 79.80 g/L.In order to improve the quality of y-PGA,single factor experiment was used to determine the best conditions of removing bacteria cells using filtering agent A,basing on physical and chemical properties of the y-PGA fermented mash.Filtering agent A was used to simulating plate and frame model to remove bacteria cells,basing on the single factor experiment.The amount of filtering agent A was studied using bacterial eliminating rate,protein concentration,y-PGA concentration as the target.The results showed that:when the fermented mash was heated 50? before diluted 4 multiples,then filtered by 1.6cm thickness(about 25g)filtering agent A four times,the bacteria cells were almost removed completely from the 130mL y-PGA fermented mash.The protein concentration was 0.32 mg/mL,the loss rate of y-PGA was 34.8%.Using the plate and frame filter,the bacteria cells were almost removed completely from the 3.4mL y-PGA fermented mash whith 1.0g filtering agent A.In order to improve the purity of y-PGA and make its application more widely,y-PGA fermented mash after removing bacteria cells was purified through the way of decolorizing,removing irons,concentrating and drying.The optimum technological conditions adsorption agent B as follows:adsorption agent B 0.7%,decolorization speed 80 r/min,decolorization time 15 min.The best order of fermented liquid though the ion exchange resin was acidic ion exchange resin first,alcaline ion exchange resin last.Small molecules could be removed completely 3 times after the process of enrichment-dilution-enrichment of membrane.White flake material was obtained by using the technology of the drying.After purification the final yield of ?-PGA was 1.56%.In the end,properties and purity of y-PGA were researched.The product was detected by UV and IR,we could see that the polymer's largest ultraviolet absorption wavelength was located in 216 nm and it coincided with ?-PGA's,so the polymer wasn't protein or nucleic acid;the sample had a series of characteristic absorption and though it the sample could be determined to ?-PGA.By high performance liquid chromatography(HPLC)analysis available:the sample only had one obvious absorption peak,indicated that the sample reached a certain purity;The molecular weight of ?-PGA was 1095kDa determined by GPC and its degree of polymerization was high. |
PDF Full Text Request