One-Pot Bioconversion of Lignin-Derived Substrates into Gallic Acid.

Lignin is regarded as the most abundant renewable aromatic compound on earth. In this study, we established -based whole-cell biocatalytic systems to efficiently convert two lignin-derived substrates (ferulic acid and -coumaric acid) to gallic acid. For the synthesis of gallic acid from ferulic acid, we used the recombinant expressing feruloyl-CoA synthetase and enoyl-CoA hydratase/aldolase from , aldehyde dehydrogenase (HFD1) from , vanillic acid -demethylase (VanAB) from and a mutant version of -hydroxybenzoate hydroxylase (PobA) from . Under the fed-batch mode, 19.57 mM gallic acid was obtained from 20 mM ferulic acid with a conversion rate of 97.9%. To achieve gallic acid synthesis from -coumaric acid, we replaced VanAB with the two-component flavin-dependent monooxygenase (HpaBC) from . Under optimal conditions, 20 mM -coumaric acid afforded the production of 19.96 mM gallic acid with near 100% conversion. To the best of our knowledge, our work represented the first study to develop -based whole-cell biocatalysts for the eco-friendly synthesis of gallic acid from lignin-derived renewable feedstocks.