Directed breeding of an Arthrobacter mutant for high-yield production of cyclic adenosine monophosphate by N+ ion implantation

To obtain a cyclic adenosine monophosphate (cAMP) high-yield production strain, Arthrobacter NG-1 was mutated by N+ ion implantation with an energy level of 10 keV and dose of 7×1015 ions/cm2. Combined with directed screening methods, a xanthine-defective and 8-azaguanine (8-AG)-resistant mutant Arthrobacter A302 was selected. The concentration of cAMP produced by this mutant was 41.7% higher than that of the original strain and reached 9.78 g/L. Through ten-generation investigation, the capability of cAMP production of A302 was found to be stable. Compared with the original strain, the special activities of key enzymes in A302, which influenced the cAMP biosynthesis, was analyzed. IMP dehydrogenase activity was defective, whereas PRPP amidotransferase, sAMP synthetase and adenylate cyclase activities were increased by 61.5%, 147% and 21.7%, respecitively, which might explain the mutagenesis mechanism by N+ ions implantation under the enzymatic level.