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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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 and
2,*
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 (CC BY 3.0).
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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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