Effect of Amplification of Desensitized purF and prs on Inosine Accumulation in Escherichia coli

摘要

The effect of a phosphoribosylpyrophosphate(PRPP)synthetase gene(prs)that was desensitized to feedback inhibition by ADP on inosine accumulation was investigated using an inosine-producing mutant of Escherichia coli.At the same time,various types of plasmid having a PRPP amidotransferase gene(purF)that was desensitized to feedback inhibition by AMP and GMP were also investigated to improve inosine productivity using a compatible plasmid containing prs with a plasmid containing purF.The recombinant E.coli 1-9 harboring a low-copy-number plasmid having the desensitized-pwrF(pMWKQ)accumulated 3.6 g/l inosine from 40 g/l glucose in a 2-d culture.Furthermore,desensitized-prs amplification,in addition to purF,resulted in the accumulation of 6.2 g/l inosine.Additionally,through these experiments,a spontaneous mutant with an enhanced inosine-producing ability compared with the parent strain 1-9 was obtained.The spontaneous mutant I-9m harboring only pMWKQ and I-9m harboring both pMWKQ and pSTVDA(a plasmid having the desensitized-prs)accumulated 6.7 g/l and 7.5 g/l inosine,respectively,from 40 g/l glucose in a 3-d culture.