Preparation method of gamma-aminobutyric acid, whole-cell catalyst and application
A whole cell catalyst, aminobutyric acid technology, applied in the whole cell catalyst and application, the field of preparation of γ-aminobutyric acid, can solve the problems of low γ-aminobutyric acid content, unsatisfactory glutamic acid decarboxylase conversion rate and the like , to achieve the effect of being conducive to maintenance, activity and stability, and avoiding the formation of inclusion bodies
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[0043] The preparation method of a kind of γ-aminobutyric acid provided in the embodiment of the present invention comprises the following steps:
[0044]S1) Preparation of whole-cell catalyst: using the autotransporter AIDA-1 as a carrier protein, the expression of glutamate decarboxylase is displayed on the cell surface to obtain a whole-cell catalyst;
[0045] S2) Preparation of γ-aminobutyric acid: L-glutamic acid or its salt is used as the substrate, catalyzed and converted under the action of whole cell catalyst to generate γ-aminobutyric acid.
[0046] Using surface expression display technology, the expression of glutamate decarboxylase is displayed on the cell surface, so that in the process of catalytic conversion, the glutamate decarboxylase expressed on the cell surface can directly react with the substrate to avoid intracellular expression. Compared with intracellularly expressed enzyme proteins, the surface expression display method is more conducive to the foldi...
Embodiment 1
[0068] Example 1: Whole cell catalyst preparation
[0069] 1) Recombinant expression plasmid:
[0070] Primers were designed according to the gene sequence of glutamate decarboxylase gadB encoded by Escherichia coli str.K-12substr.MG1655 reported in GenBank.
[0071] Forward primer: 5'-CGGggtaccATGGATAAGAAGCAAGTAACGG-3'
[0072] Reverse primer: 5'-GCgagctcGGTATGTTTAAAGCTGTTCTGTTG-3'
[0073] The target gene was amplified by DNA polymerase Pfu using Escherichia coli genome as template, and the PCR product size was 1415bp. The target fragment was recovered and digested with the restriction enzymes KpnI and SacI together with the plasmid pAIDA1. The obtained target gene fragment was connected to the vector backbone overnight, and then transferred to Escherichia coli DH5α competent cells and coated on a chloramphenicol-resistant plate. , incubate overnight at 37°C upside down. Then single colonies were identified by colony PCR with forward and reverse primers, and double-enzym...
Embodiment 2
[0083] Example 2: Whole-cell catalytic preparation of γ-aminobutyric acid
[0084] In a 20L transformation tank, put 400g of the whole-cell catalyst obtained in Example 1, 374g of sodium glutamate monohydrate, and 164g of sodium acetate, add water to dissolve, adjust the pH value to 5.0 with acetic acid, set the volume to 10L, and heat up to 37 ℃, 2 g of magnesium chloride hexahydrate and 0.26 g of PLP (pyridoxal phosphate) were put in, and the conversion was started. During the biotransformation process, the temperature was controlled at 35 to 40°C, and the rotational speed was controlled at 250 rpm.
[0085] When the pH begins to rise, add glutamic acid to control the pH at 5.4 to 5.6, and control the content of L-glutamic acid to be below 5 g / L during the process; the pH rises slowly in the later stage of the reaction, and the foam gradually decreases, stop adding L-glutamic acid; then use a small amount of sulfuric acid to control the pH value, and the reaction ends when ...
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