Development of a Commercially Viable Itaconic Acid Fermentation Process

Methacrylates are currently produced from petrochemical feedstocks and are used to manufacture a range of bulk and specialist polymers. For example, methylmethacrylate (2-methylpropenoic acid methyl ester) is used as the monomer for polymethylmethacrylate, a transparent, UV-resistant, biocompatible polymer which can easily be recycled. The polymer and its blends are used for numerous applications, such as construction, paints, coatings, automotive components, biomedical materials and as Perspex and Plexiglas, thus supporting a large, diverse supply chain. The acrylics industry requires 2000 kilotonnes of methylmethacrylate annually and the market size is 3 Billion USD. Lucite International has over 35% of the global market share for methacrylate monomers, methyl methacrylate and methacrylic acid, with 28% of their production in the UK. Therefore, methacrylate manufacturing and use provides an important contribution to the UK economy. The dependence on petrochemical feedstocks is an increasing risk factor for the future sustainability of the acrylics industry. Oil reserves are rapidly being depleted, and this is already causing increased feedstock costs. Longer term, there are concerns over the availability of feedstock supplies. Therefore, a transition to renewable feedstocks will be required to 'future-proof' the supplies of methacrylate monomers. Lucite is exploring the potential to introduce a new Hybrid Bio- and Chemocatalytic Process to produce methacrylic acid from renewable feedstocks. The proposed process involves production of organic acids by fermentation, followed by base-catalysed decarboxylation to produce methacrylic acid in near- or supercritical water. The great advantage is that both processes operate in water. This avoids the need to separate the organic acid from the fermentation broth, which would otherwise require a costly crystallization process. The chemocatalytic stage has already been developed successfully in an EPSRC-funded CASE project at the University of Nottingham, using itaconic acid and citramalic acid as substrates. The aim of this project is to develop an improved route to produce itaconic acid by fermentation and to demonstrate that raw fermentation broth can be fed directly into the hot water process, after removing the cells. The traditional itaconic acid fermentation depends on the use of filamentous fungi, and is reasonably efficient. However, there are mass transfer problems both within the fermentation process (because the fungi grow as pellets) and at the intracellular level, because aconitate has to be transferred from the mitochondria to the cytoplasm. Both problems contribute to limited productivity. Furthermore, acid pH is required in the fungal process, whereas the base-catalysed Hybrid Process requires the neutral salt. Therefore, we shall develop engineered E. coli strains to produce itaconic acid. The project will include overexpression of citrate synthase, aconitate hydratase, and aconitate decarboxylase in E. coli for initial proof of concept. Subsequently, a two stage fermentation process will be developed, with initial, rapid growth to produce the biocatalyst under aerobic conditions, followed by a switch to anaerobic conditions to produce itaconate using non-growing cells. Although this will automatically suppress the downstream reactions of the TCA cycle, further metabolic engineering will be needed to develop a robust manufacturing process. Therefore, metabolic modelling will be used to design strains which produce itaconic acid precursors efficiently, and which do not divert the precursors and product into unproductive metabolism. Some of the preliminary designs will be constructed and tested in the Hybrid Process for methacrylic acid production. This will provide a platform for future follow-on projects to construct metabolically engineered biocatalysts, based on the designs, and to develop a fully integrated Hybrid Process