A Biofactory for the Production of High Impact Flavour and Fragrance Compounds

Volatile organo-sulphur compounds (VOSCs) are high impact flavour and fragrances (F&Fs), with their natural variants being premium-valued fine chemicals. The objective of this three year project is to harness plant and microbial diversity in biocatalysis to derive a novel bioprocess for the commercial production of VOSCs from natural feed-stocks. Due to the specialized nature of the F&F market, the innovative process being developed is designed to be applicable to the sustainable production of a range of VOSCs using bioreactor technology. The project is led by Oxford Chemicals Ltd (OCL), a world player in high impact F&F fine chemicals and brings together the expertise in sulphur natural product biochemistry (Centre for Bioactive Chemistry, Durham University), applied biocatalysis (Novacta Biosystems) and bioreactor operation (Centre for Processing Innovation). The approach to be adopted is based on a two-tiered strategy. In objective 1 (0-18 months) we will develop an enzyme based bioprocess for the scaled up production of VOSCs from natural product precursors. This objective will deliver the capability of producing new high impact aroma chemicals (HIACs) within 18 months of the start of the project. In objective 2. (12- 36 months) we will develop fermentation technology to renewably produce VOSC precursors from basic naturl feedstocks. This objective will deliver the means to sustaniably produce VOSC precursors using novel metabolic engineering and will provide the consortium with new enabling technology to produce natural HIACs. The technical approach has been to establish a method for bioproduction which can produce a diverse range of VOSC chemistries using a conserved central metabolic pathway with custom enzymes controlling the entrance of substrates and the exit of products. The programme proposes to introduce sulphur into reactive natural products acceptor molecules found in essential oil components or plant concentrates using the tripeptide glutathione (?-Glu-Cys-Gly) as the donor. This 'entry' reaction will be catalysed by plant glutathione transferases. Using recombinant bacteria, the resulting glutathione conjugates will then be processed through a core metabolic pathway which sequentially hydrolyses the glutamate and glycine moieties to leave a simple cysteine conjugate. In the final stage of the process, the cysteine conjugates are then acted on by the 'exit' C-S lyase enzymes which cleave the cysteine conjugate, leaving the sulphur atom incorporated into the VOSC. All end products and by-products of the proposed pathway are of commercial value with the process both reducing waste and minimizing energy usage. The role of the Durham University academic partner within this consortium is to develop the basic science and technology (biocatalyts & metabolic engineering expertise) required for the applied production of VOSCs using bioreactor technology.