Dataset Information

Extracellular expression of glutamate decarboxylase B in Escherichia coli to improve gamma-aminobutyric acid production.

ABSTRACT: Escherichia coli overexpressing glutamate decarboxylase GadB can produce gamma-aminobutyric acid with addition of monosodium glutamate. The yield and productivity of gamma-aminobutyric acid might be significantly improved if the overexpressed GadB in E. coli cells can be excreted outside, where it can directly transforms monosodium glutamate to gamma-aminobutyric acid. In this study, GadB was fused to signal peptides TorA or PelB, respectively, and overexpressed in E. coli BL21(DE3). It was found that TorA could facilitate GadB secretion much better than PelB. Conditions for GadB secretion and gamma-aminobutyric acid production were optimized in E. coli BL21(DE3)/pET20b-torA-gadB, leading the secretion of more than half of the overexpressed GadB. Fed-batch fermentation for GadB expression and gamma-aminobutyric acid production of BL21(DE3)/pET20b-torA-gadB was sequentially performed in one fermenter; 264.4 and 313.1 g/L gamma-aminobutyric acid were obtained with addition of monosodium glutamate after 36 and 72 h, respectively.

SUBMITTER: Zhao A

PROVIDER: S-EPMC4993724 | biostudies-literature | 2016 Dec

REPOSITORIES: biostudies-literature

ACCESS DATA

Publications

Extracellular expression of glutamate decarboxylase B in Escherichia coli to improve gamma-aminobutyric acid production.

Zhao Anqi A Hu Xiaoqing X Li Ye Y Chen Cheng C Wang Xiaoyuan X

AMB Express 20160822 1

Escherichia coli overexpressing glutamate decarboxylase GadB can produce gamma-aminobutyric acid with addition of monosodium glutamate. The yield and productivity of gamma-aminobutyric acid might be significantly improved if the overexpressed GadB in E. coli cells can be excreted outside, where it can directly transforms monosodium glutamate to gamma-aminobutyric acid. In this study, GadB was fused to signal peptides TorA or PelB, respectively, and overexpressed in E. coli BL21(DE3). It was foun ...[more]

PMID: 27549808

Similar Datasets

Project description:BackgroundGamma (γ)-Aminobutyric acid (GABA) as a bioactive compound is used extensively in functional foods, pharmaceuticals and agro-industry. It can be biosynthesized via decarboxylation of monosodium glutamate (MSG) or L-glutamic acid (L-Glu) by glutamate decarboxylase (GAD; EC4.1.1.15). GADs have been identified from a variety of microbial sources, such as Escherichia coli and lactic acid bacteria. However, no GADs from Streptomyces have been characterized. The present study is aimed to identify new GADs from Streptomyces strains and establish an efficient bioproduction platform for GABA in E. coli using these enzymes.ResultsBy sequencing and analyzing the genomes of three Streptomyces strains, three putative GADs were discovered, including StGAD from Streptomyces toxytricini NRRL 15443, SsGAD from Streptomyces sp. MJ654-NF4 and ScGAD from Streptomyces chromofuscus ATCC 49982. The corresponding genes were cloned from these strains and heterologously expressed in E. coli BL21(DE3). The purified GAD proteins showed a similar molecular mass to GadB from E. coli BL21(DE3). The optimal reaction temperature is 37 °C for all three enzymes, while the optimum pH values for StGAD, SsGAD and ScGAD are 5.2, 3.8 and 4.2, respectively. The kinetic parameters including V max , Km, k cat and k cat /Km values were investigated and calculated through in vitro reactions. SsGAD and ScGAD showed high biocatalytic efficiency with k cat /Km values of 0.62 and 1.21 mM- 1·s- 1, respectively. In addition, engineered E. coli strains harboring StGAD, SsGAD and ScGAD were used as whole-cell biocatalysts for production of GABA from L-Glu. E. coli/SsGAD showed the highest capability of GABA production. The cells were repeatedly used for 10 times, with an accumulated yield of 2.771 kg/L and an average molar conversion rate of 67% within 20 h.ConclusionsThree new GADs have been functionally characterized from Streptomyces, among which two showed higher catalytic efficiency than previously reported GADs. Engineered E. coli harboring SsGAD provides a promising cost-effective bioconversion system for industrial production of GABA.

Dataset Information

Extracellular expression of glutamate decarboxylase B in Escherichia coli to improve gamma-aminobutyric acid production.

Publications

Extracellular expression of glutamate decarboxylase B in Escherichia coli to improve gamma-aminobutyric acid production.

Similar Datasets

OmicsDI is part of the ELIXIR infrastructure

Tweets