In this study, an inosine-producing strain Escherichia coli INO4-5 was used as the starting strain, and the metabolic flow of inosinic acid (IMP) node was optimized in view of the high content of byproducts, low inosine production and the requirement of additional adenine during fermentation. Firstly, the purAbsu gene from Bacillus subtilis was expressed using different promoters and ribosome binding sites to strengthen the adenosine synthesis branch, which enabled the strain to produce 29.5 g/L inosine in 5 L fermentor without extra addition of adenine. Then, the original promoter of guaB gene was replaced to weaken the guanosine synthesis branch and guaC gene was overexpressed to promote guanylic acid reflux to IMP, which significantly reduced the byproduct content of the strain and increased the inosine production to 35.1 g/L. Finally, different 5'-nucleotidases were screened and enhanced, and the introduction of specific 5'-nucleotidase gene (ISN1) from Saccharomyces cerevisiae was found to effectively promote inosine production. The resulting strain INO7-6 produced 41.2 g/L inosine with yield of 0.17 g/g glucose and productivity of 0.86 g/(L·h) in 5 L fermentor. The inosine production of this strain is the highest within the genetically engineered strains reported so far, laying a good foundation for the industrial production of inosine.
LIU Tiezhong
,
GAO Zhiqiang
,
HOU Dexin
,
XIE Xixian
,
WU Heyun
. Inosinic acid node metabolism optimization for efficient synthesis of inosine in Escherichia coli[J]. Food and Fermentation Industries, 2024
, 50(4)
: 44
-50
.
DOI: 10.13995/j.cnki.11-1802/ts.035599
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