Development of carboxyl methyltransferases for sustainable synthesis

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The research proposed aims to provide new sustainable processes for the production of chemicals using nature's catalysts, enzymes. In particular we will focus on an enzyme that is able to catalyse the production of chemicals called esters, which are ubiquitous in chemical products such as pharmaceuticals and also important as chemical intermediates for synthetic processes. The formation of an ester from an acid often involves energy demanding processes or the use of toxic chemicals and the reactions must be done in the absence of water. The enzyme under development in this project will allow the formation of esters under aqueous conditions, making it compatible with other enzyme catalysts and allowing the development of biological synthetic pathways for chemical synthesis, or cascades. In this project, we will develop highly efficient mutants of the ester forming enzyme that are able to catalyse the formation of key intermediates for the syntheis of bioplastics and pharmaceuticals. We will use state-of-the-art screening technology that is already in use in our laboratories to identify the mutants. We will then couple the new enzymes with other smaller enzyme cascades that we have already developed for the synthesis of biodegradable bioplastics from biorenewable materials such as cellulose and lignin. We will also develop new cascades for the synthesis of pharmaceuticals by coupling with other new enzymes we have discovered recently that are surprisingly able to catalyse the formation of amide bonds in water. Amide bonds are important bonds within pharmaceuticals. The combination of the ester formation followed by the amide formation will enable replacement of expensive coupling reagents used in conventional amide bond synthesis. The ester forming enzyme needs a specific molecule found in cells called SAM to act as a catalyst. We will develop optimised cell hosts (so-called microbial cell factories) to produce all the required enzymes and the SAM, such that cell fermentations can be used to carry out the synthesis of the target chemicals. We will demonstrate a fermentation for the conversion of waste plastic, PET, into a pharmaceutical drug. We also will develop cells able to metabolise methanol that will drive the synthesis and a novel strain that can recycle the methanol produced in the amide bond forming reaction which is used by the ester forming enzyme making the whole process able to function with very small amounts of methanol.