Enzymatic Production of .GAMMA.-Aminobutyric Acid Using Rice(Oryza sativa) Germ.

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Abstract
Production of γ-aminobutyric acid (GABA), which shows an antihypertensive effect, from glutamate was investigated using rice germ or bran as enzyme (glutamate decarboxylase; GAD) sources. GAD activity in the rice germ was dependent on the concentrations of glutamate and pyridoxal phosphate. The maximum activity in the germ was estimated to be 8.8 μmol/min/g. By a pH-controlled batch reaction using the rice germ, we produced 29.0 g of GABA per 100 g of the germ by incubation for 6 h at 40°C, with the conversion rate of 87.9% . The rice bran was also an effective catalyst for GABA production. These results suggested that our methods are efficient for manufacturing GABA, which is useful in the development of functional foods to manage hypertension.