One-Pot Bioconversion of Lignin-Derived Substrates into Gallic Acid
Bixia Fu, Gezhi Xiao, Yang Zhang, Jifeng Yuan
Abstract
Lignin is regarded as the most abundant renewable aromatic compound on earth. In this study, we established Escherichia coli-based whole-cell biocatalytic systems to efficiently convert two lignin-derived substrates (ferulic acid and p-coumaric acid) to gallic acid. For the synthesis of gallic acid from ferulic acid, we used the recombinant E. coli expressing feruloyl-CoA synthetase and enoyl-CoA hydratase/aldolase from Pseudomonas putida, aldehyde dehydrogenase (HFD1) from Saccharomyces cerevisiae, vanillic acid O-demethylase (VanAB) from P. putida, and a mutant version of p-hydroxybenzoate hydroxylase (PobAY385F) from P. putida. 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 p-coumaric acid, we replaced VanAB with the two-component flavin-dependent monooxygenase (HpaBC) from E. coli. Under optimal conditions, 20 mM p-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 E. coli-based whole-cell biocatalysts for the eco-friendly synthesis of gallic acid from lignin-derived renewable feedstocks.