Background Syringic acid (SA) is a high-value natural compound with diverse biological activities and wide applications, commonly found in fruits, vegetables, and herbs. SA is primarily produced through chemical synthesis, nonetheless, these chemical methods have many drawbacks, such as considerable equipment requirements, harsh reaction conditions, expensive catalysts, and numerous by-products. Therefore, in this study, a novel biotransformation route for SA production was designed and developed by using engineered whole cells.
Results An O-methyltransferase from Desulfuromonas acetoxidans (DesAOMT), which preferentially catalyzes a methyl transfer reaction on the meta-hydroxyl group of catechol analogues, was identifed. The whole cells expressing DesAOMT can transform gallic acid (GA) into SA when S-adenosyl methionine (SAM) is used as a methyl donor. We constructed a multi-enzyme cascade reaction in Escherichia coli, containing an endogenous shikimate kinase (AroL) and a chorismate lyase (UbiC), along with a p-hydroxybenzoate hydroxylase mutant (PobA**) from Pseudomonas fuorescens, and DesAOMT; SA was biosynthesized from shikimic acid (SHA) by using whole cells catalysis. The metabolic system of chassis cells also afected the efciency of SA biosynthesis, blocking the chorismate metabolism pathway improved SA production. When the supply of the cofactor NADPH was optimized, the titer of SA reached 133 μM (26.2 mg/L).
Conclusion Overall, we designed a multi-enzyme cascade in E. coli for SA biosynthesis by using resting or growing whole cells. This work identifed an O-methyltransferase (DesAOMT), which can catalyze the methylation of GA to produce SA. The multi-enzyme cascade containing four enzymesexpressed in an engineered E. coli for synthesizing of SA from SHA. The metabolic system of the strain and biotransformation conditions infuenced catalytic efciency. This study provides a new green route for SA biosynthesis.
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