(246d) Biocatalytic Amine Transfer to Lignin-Derived Carboxylic Acids and Aldehydes

The selective introduction of nitrogen heteroatoms within deconstruction products of lignin could generate building blocks that are attractive for materials applications. Here, we built and characterized enzyme cascades that create primary amines from diverse model lignin deconstruction products using a carboxylic acid reductase (CAR) and an omega-transaminase (TA). We achieved several advances over existing knowledge of these enzymes, including successful activity on substrates not previously reported. These include molecules that are functionalized with acrylate and methacrylate groups to be polymerization-ready by RAFT methods, where amine sidechains are difficult to obtain using traditional synthesis. In addition, we performed detailed characterization of cell-free and resting whole-cell reactions, ultimately overcoming bottlenecks in resting whole-cell reactions to achieve 97% yield in comparison to 75.38% using cell free system, which is very much dependent on exogenous supply of expensive cofactors. We also demonstrated the recyclability of resting whole-cells for multiple batches of catalysis without significant loss in productivity proving robustness of whole cell biocatalysts. Finally, we used the knowledge gained from this study to produce several amines from carboxylic acid precursors for the first time using one-pot biocatalytic reactions, including (meth)acrylate vanillyl amine. These results show how biocatalysts can enable green synthesis of higher-value monomers for eventual production of macromolecules from waste biomass.