Chemically Defined Medium for the Accumulation of Intracellular Malate Dehydrogenase by Streptomyces aureofaciens.

A chemically defined medium was developed for the production of intracellular malate dehydrogenases by Streptomyces aureofaciens NRRL-B 1286. The composition of the medium (per liter) was as follows: 50 g of starch, 4 g of ammonium sulfate, 7.32 g of l-aspartic acid, 13.8 g of MgSO(4) . 7H(2)O, 1.7 g of K(2)HPO(4), 0.01 g of ZnSO(4) . 7H(2)O, 0.01 g of FeSO(4) . 7H(2)O, 0.01 g of MnSO(4) . H(2)O, and 0.005 g of CoSO(4) . 7H(2)O. The pH of the medium was adjusted to 6.7 to 7.0 after sterilization. The activity of the intracellular malate dehydrogenases of the crude cell extract was greatest after 40 h of mycelium growth in a rotary shaker at 30 degrees C. The best temperature for the enzyme reactions was approximately 35 degrees C for NAD activity at pH 9.7 and 40 degrees C for NADP -linked enzyme at pH 9.0. The NAD activity required Mg, and both activities were sensitive to SH-group reagents. The NADP -dependent activity remained completely stable, and the NAD -dependent activity decreased to a very low residual level after 30 min at 60 degrees C.