Engineering Escherichia coli for Efficient Biosynthesis of Gadusol
Abstract:Gadusol as a cyclohexenone compound has attracted intensive attention  because of its sunscreen and antioxidant properties. However, its limited  availability especially from microbial cell factories hinders its applications. Here,  we systematically engineered Escherichia coli for the efficient biosynthesis of  gadusol. First, the gadusol biosynthesis pathway was reprogrammed in E. coli,  yielding an initial titer of 45.2 mg/L. Then, a novel robust colorimetric assay was  developed for high-throughput quantification of gadusol. Through a sRNA  library screening approach, the pivotal regulatory targets were rapidly identified  and regulated, resulting in 700 mg/L of gadusol. Next, after directed evolution  of the committed enzyme TktA and optimization of the availability of cofactors  NAD+ and adenosylmethionine, the titer of gadusol was increased to 965 mg/L.  Eventually, by applying a fed-batch fermentation strategy, the production of  gadusol reached to 4.2 g/L. The results provide a comprehensive framework  for rapid screening and construction of gadusol microbial cell factories.