Production of aspartic acid and enzymatic alteration in pyruvate kinase mutants of Brevibacterium flavum.

Abstract

A pyruvate kinase-lacking mutant of Brevibacterium flavum produced 22.6 g/liter of l-aspartic acid with glutamic acid as a by-product, when cultured for 48 hr in a medium containing 100 g/liter of glucose. The production clearly depended on the amount of biotin added. This strain, 70, was derived by several steps of mutation from wild strain 2247 producing glutamate, successively via a citrate synthase-defective glutamate auxotroph, strain 214, a prototrophic revertant, strain 15-8, producing 10 g/liter of l-aspartic acid, and an S-(2-aminoethyl)-l-cysteine-resistant mutant, strain 1-231, having low pyruvate kinase and homoserine dehydrogenase and producing lysine. Strain 70, a methionine-insensitive revertant from strain 1-231, had a normal level of homoserine dehydrogenase but no pyruvate kinase. Its citrate synthase activity was about half that of the wild strain at saturated concentrations of the substrates with Michaelis constants for oxalacetate and acetyl-CoA of 110 and 6 times as high as those of ...