Using an engineered enzyme variant to redirect the microbial pathway to produce renewable propane as opposed to butanol, scientists at the University’s Manchester Institute of Biotechnology, in collaboration with Imperial College and University of Turku, have created a synthetic pathway for biosynthesis of the gas propane. This work has significant impact in commercial production of renewable propane and developing the next generation of biofuels.
Navya Menon1, András Pásztor2, Binuraj RK Menon1, Pauli Kallio2, Karl Fisher1, M Kalim Akhtar2, David Leys1, Patrik R Jones2,3* and Nigel S Scrutton1*. Biotechnology for Biofuels, 2015; 8 (1).Show Affiliations
1BBSRC/EPSRC Centre for Synthetic Biology of Fine and Speciality Chemicals, Manchester Institute of Biotechnology, Faculty of Life Sciences, 131 Princess Street, The University of Manchester, Manchester M1 7DN, UK
2Molecular Plant Biology, Department of Biochemistry, Tykistökatu 6A 6krs, University of Turku, FI 20014 TURUN YLIOPISTO, Turku, Finland
3Department of Life Sciences, Imperial College London, Sir Alexander Fleming Building, South Kensington Campus, London SW7 2AZ, UK.
Propane (C3H8) is a volatile hydrocarbon with highly favourable physicochemical properties as a fuel, in addition to existing global markets and infrastructure for storage, distribution and utilization in a wide range of applications. Consequently, propane is an attractive target product in research aimed at developing new renewable alternatives to complement currently used petroleum-derived fuels. This study focuses on the construction and evaluation of alternative microbial biosynthetic pathways for the production of renewable propane. The new pathways utilize CoA intermediates that are derived from clostridial-like fermentative butanol pathways and are therefore distinct from the first microbial propane pathways recently engineered in Escherichia coli.
We report the assembly and evaluation of four different synthetic pathways for the production of propane and butanol, designated a) atoB–adhE2 route, b) atoB–TPC7 route, c) nphT7–adhE2 route and d) nphT7–TPC7 route. The highest butanol titres were achieved with the atoB-adhE2 (473 ± 3 mg/L) and atoB-TPC7 (163 ± 2 mg/L) routes. When aldehyde deformylating oxygenase (ADO) was co-expressed with these pathways, the engineered hosts also produced propane. The atoB-TPC7-ADO pathway was the most effective in producing propane (220 ± 3 μg/L). By (i) deleting competing pathways, (ii) including a previously designed ADOA134F variant with an enhanced specificity towards short-chain substrates and (iii) including a ferredoxin-based electron supply system, the propane titre was increased (3.40 ± 0.19 mg/L).
This study expands the metabolic toolbox for renewable propane production and provides new insight and understanding for the development of next-generation biofuel platforms. In developing an alternative CoA-dependent fermentative butanol pathway, which includes an engineered ADO variant (ADOA134F), the study addresses known limitations, including the low bio-availability of butyraldehyde precursors and poor activity of ADO with butyraldehyde.