Efficient production of guanosine in Escherichia coli by combinatorial metabolic engineering

Abstract

Guanosine is a purine nucleoside that is widely used as a raw material for food additives and pharmaceutical products. However, the lack of strains with efficiently producing guanosine greatly limited industrial application. We attempted to efficiently produce guanosinein Escherichia coli using systematic metabolic engineering. First, we overexpressed the purine synthesis pathway from Bacillus subtilis and the prs gene, and deleted three genes involved in guanosinecatabolism to increase guanosine accumulation. Subsequently, we attenuated purA expression and eliminated feedback inhibition. Then, we modified the metabolic flux of the glycolysis and Entner-Doudoroff pathways and performed redox cofactors rebalancing. Finally, transporter engineering further increased the guanosine titre to 123.6 mg/L. After 72 h of the fed-batch fermentation in shake-flask, the guanosine titre achieved 145.2 mg/L. Our results reveal that the guanosinesynthesis pathway was successfully optimized by combinatorial metabolic engineering, which could be applicable to the efficient synthesis of other nucleoside products.