Optimization of Conversion Conditions for Biosynthesizing γ-Aminobutyric Acid by Recombinant Glutamate Decarboxylase from Escherichia coli
The conditions for the synthesis of γ-aminobutyric acid (GABA) using glutamate decarboxylase from recombinant E.coli cells were optimized in this work.The effects of temperature,pH,surfactants,metal ions,the ratio of substrate and cells and the transformation system volume on the productivity of GABA were studied.Results indicated that the optimal reaction system volume was 5 mL containing 0.1 mol/L sodium glutamate as the substrate,6.4 mg of E.coli cells (dry weight),0.06％ Triton-100 (volume fraction) and 0.6 mmol/L Ca2+ at pH 4.5.The reaction was allowed to proceed for 7 h at 45 ℃.Under these optimal conditions,the yield of GABA was 26.1 g/L.The transformation efficiency of GABA reached the highest level of 13.8 g/(g·h) after 1 h reaction,which is 2.5 times higher than that observed before optimization.
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