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Int. J. Mol. Sci. 2013, 14(1), 1728-1739; doi:10.3390/ijms14011728
Article

Gamma-Aminobutyric Acid Production Using Immobilized Glutamate Decarboxylase Followed by Downstream Processing with Cation Exchange Chromatography

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1 University of Science and Technology (UST), 217 Gajeong-ro, Yuseong-gu, Daejeon 305-350, Korea 2 Biotechnology Process Engineering Center, KRIBB, 125 Gwahak-ro Yuseong-gu, Daejeon 305-806, Korea
* Author to whom correspondence should be addressed.
Received: 17 November 2012 / Revised: 1 January 2013 / Accepted: 2 January 2013 / Published: 15 January 2013
(This article belongs to the Section Biochemistry, Molecular Biology and Biophysics)
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Abstract

We have developed a gamma-aminobutyric acid (GABA) production technique using his-tag mediated immobilization of Escherichia coli-derived glutamate decarboxylase (GAD), an enzyme that catalyzes the conversion of glutamate to GABA. The GAD was obtained at 1.43 g/L from GAD-overexpressed E. coli fermentation and consisted of 59.7% monomer, 29.2% dimer and 2.3% tetramer with a 97.6% soluble form of the total GAD. The harvested GAD was immobilized to metal affinity gel with an immobilization yield of 92%. Based on an investigation of specific enzyme activity and reaction characteristics, glutamic acid (GA) was chosen over monosodium glutamate (MSG) as a substrate for immobilized GAD, resulting in conversion of 2.17 M GABA in a 1 L reactor within 100 min. The immobilized enzymes retained 58.1% of their initial activities after ten consecutive uses. By using cation exchange chromatography followed by enzymatic conversion, GABA was separated from the residual substrate and leached GAD. As a consequence, the glutamic acid was mostly removed with no detectable GAD, while 91.2% of GABA was yielded in the purification step.
Keywords: gamma aminobutyric acid; glutamate decarboxylase; glutamic acid; immobilization; cation exchange chromatography gamma aminobutyric acid; glutamate decarboxylase; glutamic acid; immobilization; cation exchange chromatography
This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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Lee, S.; Ahn, J.; Kim, Y.-G.; Jung, J.-K.; Lee, H.; Lee, E.G. Gamma-Aminobutyric Acid Production Using Immobilized Glutamate Decarboxylase Followed by Downstream Processing with Cation Exchange Chromatography. Int. J. Mol. Sci. 2013, 14, 1728-1739.

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