Enzymatic Production of D-Glu from L-Glu by Lactobacillus brevis ATCC 8287

Abstract

Enzymatic production of D-Glu was investigated by the succesive reactions of a glutamate racemase (EC 5.1.1.3) and a glutamate decarboxylase (EC 4.1.1.15) on L-Glu. Lactobacillus brevis ATCC8287 was chosen as a source of glutamate racemase. This strain produced a glutamate decarboxylase simulataneously. The glutamate racemase activity in the cell free extracts was 0.035 units/mg protein. The enzyme kept its activity even at 500 mM of L-Glu (74 g/liter). The optimum pHs of the racemase and the decarboxylase were at around 8.5 and below 4.0, respectively. Both enzymes had no activity at the optimum pH for the other enzyme. L-Glu was racemized first by the glutamate racemase at pH 8.5, then the pH was shifted to 4.0 at which L-Glu was decarboxylated by the glutamate decarboxylase. Starting from 100 g/liter of L-Glu, 50 g/liter of D-Glu was produced and no L-Glu remained in the reaction mixture.