Biocatalysis for biomass conversion to bioplastics precursors

There is a current unmet need for sustainable methods for the bioconversion of biomass derived compounds into chemical precursors for enzyme catalysed polymerisation to make bioplastics. The Carnell group at the University of Liverpool have recently reported a combination of enzymes for the efficient conversion of cellulose-derived 5-hydroxymethylfurfural (HMF) to the bioplastics precursor 2,5-furandicarboxylic acid (FDCA), an aromatic dicarboxylic acid, in a one pot continuous process. To use aromatic dicarboxylic acids as polymer building-blocks requires energy intensive processes to extract and purify the diacids to allow them to then be reacted with non-biomass obtained alcohols for esterification. The project will focus on the development of an unexploited group of methyltransferase enzymes for the direct esterification of bio-derived dicarboxylic acids such as FDCA and pyridine diacids. The majority of methyltransferases employ the ubiquitous cofactor SAM as the methyl donor to methylate a range of structurally distinct substrates including carboxylic acids. Enzymes have evolved to work under mutually compatible conditions for multi-step synthesis and methyltransferases are able to perform under the same aqueous conditions in which the diacids are formed. By forming methyl esters using methyltransferases, they are suitable for transesterification by further enzymatic action to deliver a streamlined, highly atom efficient and sustainable route to important bioplastic precursors.