Biotransforming Phenylpropanoids derived from Biorefining: a Toolkit Approach

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The use of plants as renewable feedstocks to replace petrochemicals requires similar levels of efficiency in terms of refining and recovery of useful products. In biofuel production, which is currently the most advanced refining applied to recover platform chemical from plant biomass, a considerable amount of material is non-fermentable and remains as a low value by-product at the end of the process. Fractionating this residue and adding value to its components would enhance the efficiency economics and ultimately sustainability of biorefining. One relatively abundant and easily recoverable chemical in the non-fermented material is the secondary metabolite ferulic acid, a phenylpropanoid (PP) used extensively in plants for making biologically active polyphenolic compounds. In this project we propose to use ferulic acid and other PPs as precursors to produce dihydrochalcones and their glycosylated derivatives through fermentation in metabolically engineered yeast. These dihydrochalcones are widely used as artificial sweetners and flavour masking agents in the food industry and are currently made by non-chemical transformation methods. In our process, we will reconstruct pathways which function to produce polyphenolics in plants and engineer them into yeast, which on feeding with PPs will then produce these artificial flavouring agents through a sustainable biological process. As artificial flavouring agents, the use of genetic modification to produce these compounds will not affect their market value, as they are not 'natural' products. Furthermore, the modular assembly of our engineered pathway and the feeding of specific PP pre-cursors gives us the potential to produce novel dihydrochalcones which have the potential to be developed into new flavour enhancing products for the food industry. The programme therefore will therefore add value to existing fermentation processes which utilise plant material. In addition the process would also be highly compatible with processes aimed at deconstructing lignin, which is a major non-fermentable product derived from woody biomass composed of PP intermediates. Thus the project is both of immediate utility and establishes useful technologies of longer term value to the biorefining industries which have identified lignin deconstruction and the use of the respective products as a major future commercial opportunity.