Project Outline

Lignin is an aromatic heteropolymer found in plant cell walls, and is the most abundant renewable source of aromatic carbon in the biosphere. There is considerable interest in the biorefinery concept, to convert plant biomass residues into renewable, low carbon fuels and chemicals. Lignin is challenging to break down, since it is not susceptible to hydrolytic cleavage, but Professor Bugg’s group have discovered several bacterial enzymes for lignin degradation (DyP peroxidases, multi-copper oxidases, manganese superoxide dismutase), and accessory enzymes (dihydrolipoamide dehydrogenase, glycolate oxidase), and they have pioneered the use of engineered lignin-degrading bacteria, such as Rhodococcus jostii RHA1 and Pseudomonas putida KT2440, to generate high-value bioproducts from lignin breakdown. Current areas of interest as follows:

Enzymology of lignin degradation. We have recently shown that combinations of lignin-degrading enzymes with accessory enzymes show improved yields and novel product formation from polymeric lignin [1,2]. We are therefore interested to study the molecular basis of action of lignin-degrading enzymes, especially Agrobacterium sp. LigE [1] and Rhodococcus jostii glycolate oxidase [2] using lignin model compounds, and using isotope-labelled lignin [3].

Metabolic engineering of lignin degradation to generate high-value products. We have demonstrated that engineered Rhodococcus jostii RHA1 can be used to generate pyridine-dicarboxylic acid bioproducts from lignin or lignocellulose [4,5], which are monomers for bioplastic production, in collaboration with Biome Bioplastics Ltd. We are therefore interested in strategies to improve the PDCA titre from lignin or plant biomass. We have also generated aroma chemical 4-vinylguaiacol using engineered Pseudomonas putida KT2440 [6], and are interested in generation of other flavour/aroma chemicals via that route, and fine chemical derivatives.

Projects would involve enzymology, recombinant DNA technology, and genetic modification work, together with microbial transformations of lignin, and product identification using HPLC and LC-MS.

References

[1] G.M.M. Rashid, T.D.H. Bugg, Catalysis Sci. Technol., 11, 3568-3577 (2021). [2] A. Alruwaili, G.M.M. Rashid, and T.D.H. Bugg, Green Chemistry, 25, 3549-3560 (2023). [3] A. Alruwaili, G.M.M. Rashid, V. Sodré, J. Mason, Z. Rehman, A. Menaketh, S.P. Brown, and T.D.H. Bugg, RSC Chem. Biol., 4, 47-55 (2023). [4] Z. Mycroft, M. Gomis, P. Mines, P. Law & T.D.H. Bugg, Green Chemistry, 17, 4974-4979 (2015). [5] E.M. Spence, L. Calvo-Bado, P. Mines, and T.D.H. Bugg, Microb. Cell Fact., 20, article 15 (2021). [6] J.J. Williamson, N. Bahrin, E.M. Hardiman, and T.D.H. Bugg, Biotechnology J., 15, 1900571 (2020).

Techniques

• Enzymology
• Recombinant DNA technology using Escherichia coli, Rhodococcus jostii RHA1 or Pseudomonas putida KT2440.
• Microbial biotransformations, using growing or resting cells, in shake flasks or 2.5L bioreactor.
• Analytical chemistry for bioproduct identification, using HPLC, LC-MS and GC-MS