Abstract
Corynebacterium glutamicum mutants lacking ATP phosphoribosyl transferase (PRT) were selected by complementation with the Escherichia coli PRT gene. The recombinant plasmid pCH13 carrying a wild type PRT gene from C. glutamicum T106 was obtained in one of the mutants, LH13. Transformants, LH13/pCH13 and T106/pCH13, had three times higher PRT specific activity than T106. The plasmid pCH99 specifying the PRT, which was desensitized to feedback inhibition by L-histidine fifty-fold higher than the wild type PRT, was derived from pCH13. L-Histidine productivity of C. glutamicum F81, was markedly decreased by pCH13, but increased twice by pCH99. In cultivation in jar fermentors, F81/pCH99 continued to accumulate L-histidine through fermentation and yielded to the titer of 22.5g/liter, while F81accumulated only 11.5g/liter due to production retardation halfway through fermentation. Moreover, F81/pCH99 had a larger production rate than F81 even in its production phase. These results indicate that the yield improvement results from amplification of the highly desensitized PRT provided by pCH99.
