Method for refining polyglutamic acid in biologic fermentation broth by using ultrafiltration and nanofiltration techniques

Abstract

The invention discloses a method for refining polyglutamic acid in biologic fermentation broth by using ultrafiltration and nanofiltration techniques, which belongs to the technique field of biologic synthesis and purification. Aiming at the distribution characteristics of target extracts and molecular weights of impurities in the fermentation broth, the method is used for effectively separating gamma-PGA of different molecular weights with the combination of modern film separation techniques, and the method mainly comprises the following steps: reducing the viscosity of kieselguhr, filtering and sterilizing, heating to be combined with ultrafiltration decontamination proteins and macromolecule active organisms, removing metal ions and impurities with positive charges by using a cation exchange resin, decoloring, subsequently removing micromolecule and ionic impurities in a nanofiltration mode, performing ultrafiltration and extraction at different stages so as to obtain refined gamma-PGA of different molecular weights. The extraction yield is kept greater than 92%, which is higher than the highest yield of 90.6% reported in documents, high market pertinence is achieved, production can be performed according to demands, and the economic benefits are professionally improved as gamma-PGA of different molecular weights are refined with the combination of ultrafiltration and nanofiltration techniques.

Description

Technical field: [0001] The invention belongs to the technical field of biological synthesis and purification, and in particular relates to a method for separating and purifying biodegradable macromolecular materials of different molecular weights in biological fermentation liquid—polyglutamic acid. Background technique: [0002] In today's increasingly harsh environment and increasingly scarce resources, it is particularly important to find a biodegradable biopolymer material with a wide range of uses. γ-Polyglutamic acid (γ-Polyglutamic acid) abbreviation γ-PGA is an extracellular polymer compound synthesized by certain Bacillus. It uses glutamic acid as the only monomer and is composed of L-glutamic acid (L-Glu) and D-glutamic acid (D-Glu) are a polypeptide molecule formed by the combination of amide bonds. γ-PGA is decomposed into glutamic acid by enzymes in the body and enters the tricarboxylic acid cycle without toxic side effects. In the natural environment, γ-PGA is...

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Problems solved by technology

[0003] Since the 1990s, some developed countries such as Japan and the United States have been very active in the research on the preparation and application of γ-PGA, and the technology of microbial fermentation to produce γ-PGA is also in the forefront of the world. Ajinomoto Co., Ltd., Meiji Foreign units represented by Confectionery Company and Hirosaki University have done in-depth research on the performance, synthesis and application of γ-PGA. γ-PGA has commercial products, and there are relatively few studies in this area in my country. The research on γ-PGA fermentation production has also made great progress. The research on γ-PGA mass production in mainland China is still lacking, especially in the viscous fermentation broth. For γ-PGA with a molecular weight within a certain range, the extraction of γ-PGA The efficiency of PGA is only 40-50%, resulting in a lot of waste and loss of γ-PGA

According to literature reports, most of the extraction of γ-PGA with different molecular weights is to change the fermentation conditions to produce γ-PGA with similar molecular weight as much as possible. Often the output γ-PGA is distributed within a certain molecular weight range, but in the traditional extraction process, there is no precise extraction of γ-PGA according to the molecular weight in the same batch of fermentation broth. Therefore, in the extraction process, the viscosity of the fermentation broth At the same time, how to efficiently extract γ-PGA according to different molecular weights and reduce costs in subsequent separations has always been the main problem that plagues B. licheniformis (B. licheniformis) fermentation to prepare γ-PGA, which requires great attention