Selection and activation of Escherichia coli strains for L-aspartic acid biosynthesis.

The strain of Escherichia coli K-12 with high aspartase activity was irradiated with UV. After mutagenesis and selection, the mutant B-715 was isolated which was 4-times more active in L-aspartic acid biosynthesis than parental K-12 strain. The highest productivity was achieved while the strain was cultivated in the ammonium fumarate medium in 37 degrees C for 18-30 hours. It was found that better results were obtained when before the main production step of biosynthesis of L-aspartic acid, the cells of E. coli B-715 were incubated in the activation medium with ammonium fumarate. Activation at 37 degrees C was the most advisable for high efficiency of L-aspartic acid biosynthesis. The productivity of E. coli B-715 during 1 hour biosynthesis process was at the range 0.19-0.35 g of L-aspartic acid per 1 gram of dry mass (biomass) per minute.