Professor David Leak
Profile
Current Research
We currently work on two themes: microbial metabolic engineering for production of chemicals from renewables, and bioprocessing for biopharmaceutical production. We also have long standing interests in applied biocatalysis. Much of our work is at the biology –chemistry/chemical engineering interface and has a strong focus in industrial biotechnology. We work closely with companies such as TMO Renewables and Fujifilm Diosynth and have links with a much wider network of industrial partners.
Metabolic engineering
Crop/waste lignocellulose conversion to fuels/chemicals involves inter-dependent steps: physical pretreatment; enzyme hydrolysis; fermentation and product recovery. Our work focuses on Geobacillus spp, bacteria which grow rapidly at 60-70oC on lignocellulose-derived oligomeric and monomeric carbohydrates. We worked with TMO Renewables in developing their “cellulosic” ethanol process using G. thermoglucosidasius (Cripps et al 2009). We are now creating a series of metabolic flux models, incorporating transcriptomic and 13C metabolic flux data to define strategies for making various chemicals from renewable feedstocks. We are also extending the catabolic versatility of this host to use complex carbohydrates in order to minimise the enzyme required for substrate pre-treatment, fundamental work which is being integrated with the use of real feedstocks (eg distillers dried grains, sugar beet pulp). This involves creation of new genetic tools employing a synthetic biology approach allowing the simple interchange of parts (Bartosiak-Jentys et al 2013). It also involves integrating substrate pre-treatment with the subsequent fermentation.
Bioprocessing
Pichia pastoris is a methylotrophic yeast commonly used for production of heterologous proteins including biopharmaceuticals. High heterologous protein titres can be obtained when cells are grown to very high cell density. However, the specific productivity is actually quite low and production is highly protein dependent. We are trying to unravel the rules which determine heterologous protein productivity in this host. This appears to be a combination of protein and host based factors
Publications
Bartosiak-Jentys, J., Hussein, A. H., Lewis, C. J. and Leak, D. J., 2013. Modular system for assessment of glycosyl hydrolase secretion in Geobacillus thermoglucosidasius. Microbiology, 159 (7), pp. 1267-1275.
Bartosiak-Jentys, J., Eley, K. and Leak, D. J., 2012. Application of pheB as a reporter gene for Geobacillus spp, enabling qualitative colony screening and quantitative analysis of promoter strength. Applied and Environmental Microbiology, 78 (16), pp. 5945-5947.
Xiao, Y., Liu, T.-T., Dai, H., Zhang, J.-J., Liu, H., Tang, H., Leak, D. J. and Zhou, N.-Y., 2012. OnpA, an unusual flavin-dependent monooxygenase containing a cytochrome b5 domain. Journal of Bacteriology, 194 (6), pp. 1342-1349.
Tredwell, G. D., Edwards-Jones, B., Leak, D. J. and Bundy, J. G., 2011. The development of metabolomic sampling procedures for Pichia pastoris, and baseline metabolome data. PLoS ONE, 6 (1), e16286.
Taylor, M. P., Van Zyl, L., Tuffin, I. M., Leak, D. J. and Cowan, D. A., 2011. Genetic tool development underpins recent advances in thermophilic whole-cell biocatalysts : Recent advances in thermophilic genetic systems. Microbial Biotechnology, 4 (4), pp. 438-448.
Brandt, A., 2011. Ionic liquid pretreatment of lignocellulosic biomass with ionic liquid-water mixtures P51157WO. UNSPECIFIED, 2011.
Brandt, A., Ray, M. J., To, T. Q., Leak, D. J., Murphy, R. J. and Welton, T., 2011. Ionic liquid pretreatment of lignocellulosic biomass with ionic liquid–water mixtures. Green Chemistry, 13 (9), pp. 2489-2499.
Brandt, A., Hallett, J. P., Leak, D. J., Murphy, R. J. and Welton, T., 2010. The effect of the ionic liquid anion in the pretreatment of pine wood chips. Green Chemistry, 12 (4), pp. 672-679.
Crowhurst, N. A. and Leak, D. J., 2010. Biobutanol : a better biofuel? International Sugar Journal, 112 (1334), pp. 64-73.
Ray, M. J., Leak, D. J., Spanu, P. D. and Murphy, R. J., 2010. Brown rot fungal early stage decay mechanism as a biological pretreatment for softwood biomass in biofuel production. Biomass and Bioenergy, 34 (8), pp. 1257-1262.
Leak, D. J., 2010. Venter creates synthetic life : should we be scared? Chemistry and Industry, 2010 (16), pp. 16-17.
Leak, D. J., 2009. Benchtop evolution : using forced evolution to generate gene and protein variants in the laboratory. The Biochemist, 31 (1), pp. 36-39.
Leak, D. J., Sheldon, R. A., Woodley, J. M. and Adlercreutz, P., 2009. Biocatalysts for selective introduction of oxygen. Biocatalysis and Biotransformation, 27 (1), pp. 1-26.
Jiang, X.-W., Liu, H., Xu, Y., Wang, S.-J., Leak, D. J. and Zhou, N.-Y., 2009. Genetic and biochemical analyses of chlorobenzene degradation gene clusters in Pandoraea sp. strain MCB032. Archives of Microbiology, 191 (6), pp. 485-492.
Borole, A. P., Hamilton, C. Y., Vishnivetskaya, T., Leak, D. and Andras, C., 2009. Improving power production in acetate-fed microbial fuel cells via enrichment of exoelectrogenic organisms in flow-through systems. Biochemical Engineering Journal, 48 (1), pp. 71-80.
Borole, A. P., Hamilton, C. Y., Vishnivetskaya, T. A., Leak, D., Andras, C., Morrell-Falvey, J., Keller, M. and Davison, B., 2009. Integrating engineering design improvements with exoelectrogen enrichment process to increase power output from microbial fuel cells. Journal of Power Sources, 191 (2), pp. 520-527.
Cripps, R. E., Eley, K., Leak, D. J., Rudd, B., Taylor, M., Todd, M., Boakes, S., Martin, S. and Atkinson, T., 2009. Metabolic engineering of Geobacillus thermoglucosidasius for high yield ethanol production. Metabolic Engineering, 11 (6), pp. 398-408.
Taylor, M. P., Esteban, C. D. and Leak, D. J., 2008. Development of a versatile shuttle vector for gene expression in Geobacillus spp. Plasmid, 60 (1), pp. 45-52.
Shen, Y., Yan, D.-Z., Chi, X.-Q., Yang, Y.-Y., Leak, D. J. and Zhou, N.-Y., 2008. Degradation of cyclohexylamine by a new isolate of Pseudomonas plecoglossicida. World Journal of Microbiology and Biotechnology, 24 (8), pp. 1623-1625.
Baptista, I.I.R., Emanuelsson, E. A. C., Peeva, L.G., Mantalaris, A., Livingston, A.G., Zhou, N.Y. and Leak, D.J., 2008. Evidence of species succession during chlorobenzene biodegradation. Biotechnology and Bioengineering, 99 (1), pp. 68-74.
Thompson, A. H., Studholme, D. J., Green, E. M. and Leak, D. J., 2008. Heterologous expression of pyruvate decarboxylase in Geobacillus thermoglucosidasius. Biotechnology Letters, 30 (8), pp. 1359-1365.
