Microbial conversion of lignin to monomers for bio-based plastics using synthetic biology (MILIMO)

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There is a societal need in EU countries to develop new types of bio-plastics that could be used to replace current petroleum-based plastics for a range of packaging applications. The industrial partner in this Project, Biome Bioplastics Ltd (UK), has been developing new polyester plastics containing replacements for terephthalic acid used in petroleum-based plastics such as PET or PBAT. Professor Bugg and Biome Bioplastics have developed a biocatalytic route from the biopolymer lignin, found in plant cell walls, to 2,4- and 2,5-pyridinedicarboxylic acid, which can be used as biobased replacements for terephthalic acid. This project will seek to enhance the yields of 2,4-PDCA and 2,5-PDCA from lignin, to the point where a commercially feasible method of production could be developed. The project will use synthetic biology methods to enhance the rate of lignin oxidation in two lignin-degrading bacteria: Rhodococcus jostii RHA1 and Pseudomonas putida KT2440. We will also aim to convert hydroxycinnamic acids or the cellulose fraction of lignocellulose into PDCA monomers. Synthetic biology will also be used to redesign the metabolic pathways of Pseudomonas putida KT2440 in order to optimise the production of PDCA monomers from different plant feedstocks. We will also investigate the use of consortia of different lignocelluose-degrading bacteria for the conversion of lignin into PDCA monomers, mimicking the situation in soil where consortia of lignin-degrading specialists and cellulose-degrading specialists co-operate in order to break down lignocellulosic biomass. Having developed a high-yield process for production of PDCAs on a small scale under laboratory conditions, the biocatalytic process will be scaled up to yield an efficient fermentation-based method for conversion of lignin or lignocellulose feedstocks to PDCA monomers, that could be commercialised by Biome Bioplastics.