Patent ID: 7608432

Claim:
A method for producing a purine nucleoside by fermentation comprising: culturing an Escherichia coli microorganism in a culture medium to produce and accumulate the purine nucleoside in the medium, and collecting the purine nucleoside, wherein said microorganism has purine nucleoside-producing ability and is modified to inactivate a purine repressor wherein said microorganism has purine nucleoside-producing ability and is modified to inactivate a purine repressor, said purine repressor being encoded by a gene obtained by PCR amplification employing the primer pair of SEQ ID NO: 7 and SEQ ID NO: 8 and Escherichia coli chromosomal DNA as the template wherein said microorganism is further modified to desensitize feedback inhibition of phosphoribosyl pyrophosphate amidotransferase, said phosphoribosyl pyrophosphate amidotransferase being encoded by a gene obtained by PCR amplification employing the primer pair of SEQ ID NO: 1 and SEQ ID NO: 2 and Escherichia coli chromosomal DNA as the template, and wherein said microorganism is further modified to block reactions catalyzed by purine nucleoside phosphorylase and adenosine deaminase, said purine nucleoside phosphorylase being encoded by a gene obtained by PCR amplification employing the primer pair of SEQ ID NO: 5 and SEQ ID NO: 6 and Escherichia coli chromosomal DNA as the template, and said adenosine deaminase being encoded by a gene obtained by PCR amplification employing the primer pair of SEO ID NO: 11 and SEO ID NO: 12 and Escherichia coli chromosomal DNA as the template.