Abstract
Biofuels
are the current, commercial solution to mitigating dependence on fossil
petroleum and are fundamental for the transition to a low carbon economy.
Existing biofuels – alcohols and biodiesels – are derived from plant sugars or
oils, mixed with gasoline and diesel respectively. So called “blend walls”
limit the amounts of biofuels that can be added to fossil petroleum
distillates. Moreover, the use of comestible sugars and vegetable oils as the
precursors for biofuels diverts much needed calories from food to fuel and
alters food production and markets on a global scale.
We
used Synthetic Biology to design and construct artificial metabolic pathways
for the production of fuel molecules that are structurally identical to fossil
fuels; i.e. bio-alkanes and -alkenes of varying C-chain lengths and branching
configurations. However, a number of challenges remain before such solutions
can be deployed in the marketplace, notably the improvement of
biomass-degrading and hydrocarbon synthesis enzymes, the identification of
reliable and predictable molecular control systems and the “domestication” of
bacterial hosts that are compatible with industrial fermentation.
The
thermophile, Geobacillus thermoglucosidans, is a promising candidate for
development as an industrial microbial host and has previously been engineered
for bioethanol production. G. thermoglucosidans grows between 40 – 70 °C, can
naturally degrade a variety of biomass sugars, is genetically competent and
belongs to a large genus with a number of sequenced genomes.
This
seminar will use G. thermoglucosidans as a model case-study to describe the
challenges and opportunities of deploying new, non-model bacteria for
industrial-scale biofuels production.
Production
of fuel-grade alkanes in engineered bacteria: Synthetic, molecular modules (in
green, blue and red) were engineered into bacteria to transform the native
fatty acid pool (in black) to bio-alkanes of different sizes and chemical
properties. The green module is used to generate branched products, the blue
module to change the C-chain length and the red module to generate the
bio-alkanes. Rectangles represent genes; circles denote metabolites.