Method for extracting and purifying polyglutamic acid

Abstract

The invention discloses a method for extracting and purifying polyglutamic acid by adjusting the pH value to carry out fractional precipitation in the presence of ammonium sulfate. The method comprises the following steps: adding 30-60% (W / V) of ammonium sulfate into a fermentation liquid containing polyglutamic acid, adjusting the pH value to 6.0-8.0, removing the precipitate after stirring, andcollecting the glutamic acid clear solution; adjusting the pH value of the polyglutamic acid clear solution to be acidic, and collecting the glutamic acid precipitate; then re-dissolving the polyglutamic acid precipitate with water, adjusting the pH value to be alkalescent by using an alkali, carrying out ultrafiltration until conductivity of the permeate liquid is smaller than 5 ms*cm, and collecting the retained liquid; and adding activated carbon into the retained liquid for decolorization to obtain a colorless clear liquid, and carrying out drying to obtain a white polyglutamic acid solid.According to the method, polyglutamic acid can be effectively separated with other impurities, and use of organic solvents such as ethanol and the like is avoided. The purity of the obtained polyglutamic acid is high, and production cost is effectively reduced.

Description

Technical field:

[0001] The invention belongs to the field of biotechnology, and in particular relates to a method for extracting and purifying polyglutamic acid. Background technique:

[0002] γ-polyglutamic acid is a water-soluble extracellular glutamic acid polymer produced by microbial fermentation [γ-polyglutamic acid, referred to as γ-PGA], generally referred to as polyglutamic acid in Chinese, and its relative molecular weight is generally between 100-2000KDa . Depending on the molecular weight, its application fields are also different, such as in soil modification, water flocculation, cosmetics, medicine, etc. Generally, the larger the molecular weight, the higher the viscosity. Due to the high viscosity of polyglutamic acid, separation and purification are extremely difficult. The purification methods reported so far mainly include organic solvent precipitation method, heavy metal precipitation method, alcohol-free purification method, etc. The organic solvent p...