Purification And Applications Of Poly-?-glutamic Acid From Bacillus Licheniformis

Poly-y-glutamic acid(y-PGA)is a natural,versatile and biodegradable biopolymer that is water-soluble,edible,and environment-friendly.In this study,y-PGA produced from Bacillus licheniformis CGMCC 2876 was separated,purified and characterized.Futherermore,the applications of y-PGA from this strain were investigated.Firstly,the separation and purification of y-PGA from B.licheniformis CGMCC 2876 was investigated.The crude product was obtained by the process of the separation including removing strain and ethanol precipitation.The purity and yield of it were 60.7%and 28.6 g·L-1,respectively.Afterwards,the purified puoduct was gained with ion exchange column chromatography and gel chromatography.The purity and yield of purified product were 93.8%and 4.79 g·L-1,respectively.And the molecular weight of purified product was distributed in the vicinity of 1700 kDa.Secondly,the properties of the y-PGA were researched by some characterization methods.With the ultraviolet and analysis of protein concentration,it showed that there was no protein,nucleic acids and other impurities in the purified product.With the infrared,elemental analysis and nuclear magnetic resonance,it was discovered that the polymer was polyamid which contained 33.36%C and 7.82%N.With the mass thermogravimetry,the purified puoduct exhibited excellent heat resistance because the temperature of thermal decomposition could be up to 300 ?.At last,the applications of these two kinds of products were studied.In the process of waste leachate treatment,the COD and turbidity were decresed by 19.56%and 98.01%,respectively,in 5 mins with the addtion of 0.2 g·L-1 ?-PGA,and the particle size changed from 20 ?m to 60 ?m in the pH=12.Compared with the polyacrylamide,the COD degradation rate was 4.34%higher and the turbidity was identical.This research also studied the water retention and water absorption capabilities of the purified product.Compared with the glycerin,the results showed that the moisture and water-absorption rate were improved by 10.79%and 7.47%,respectively,when the relative humidity was 43%.Similarly,the moisture and water-absorption rate were 5.05%and 6.29%greater than glycerin,respectively.When the relative humidity decreased from 81%to 43%,the reduction of the moisturizing and water-absorption rate were 2.28%and 17.13%lower than glycerol,respectively.