Exploring the biotechnological potential of the UbiD (de)carboxylase family: novel biochemistry for renewable commodity chemicals

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The projected depletion of fossil oil resources, and the threat of global warming as a direct consequence of their continued use, has led to the challenge of providing alternative and renewable routes to oil derived fuels and commodity chemicals. However, any such process faces severe demands in terms of yield and costs before it can be considered industrially relevant. In addition, the production of oil derived compounds (ie hydrocarbons) or their functionalization does not belong to what can be considered the "standard" biochemical repertoire. Hence, comparably few biocatalysts, pathways or organisms have been reported to might support such processes. Therefore, while the challenge is clearly defined, the route to a suitable solution if far from clear, and there is an unmet industrial need for new biocatalysts that can produce commodity chemicals such as butadiene (precursor to synthetic rubber) and aromatic dicarboxylic acids (precursors to PET and other polymers). We have recently been able to provide some detailed insights into the mechanism of the UbiD family of enzymes. These act as reversible decarboxylates (ie adding or removing a CO2 group to/from an organic molecule). We and others have shown they are able to interconvert unsaturated hydrocarbons (ie containing a double bond) with the corresponding carboxylic acids (ie version containing the additional CO2 group). A wide range of substrates has been reported, and the reaction catalysed appears readily reversible depending on [CO2] levels. Our recent work on these enzyme has established the achieve this unusual chemistry by making use of a previously unknown enzyme cofactor. In this project, we seek to complete our understanding of how this cofactor is made, and also how it is inactivated, to guide future application.Building on our fundamental understanding, we seek to derive novel and green production routes to commodity chemicals using renewable feedstocks as UbiD substrates. More specifically, in this grant we will seek to establish to what extend UbiD enzyme can be evolved to produce compounds such as butadiene and aromatic dicarboxylic acids. We will make use of the renewable feedstocks muconic and benzoic acid as UbiD substrates respectively. Our results will provide proof of concept and outline the scope for future biotechnological application.