Download the Algal Biofuels Roadmap draft document - Sandia

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evolution of microalgae, and these are likely to have significant effects on metabolic
pathways and regulation of fuel precursor synthesis. For example, fatty acid synthesis,
which occurs in the chloroplast, is at least partly regulated by nuclear-encoded gene
products, and there are fundamental differences in the interaction between the nucleus
and chloroplast in algae with different extents of endosymbiosis (Wilhelm, Buchel et al.,
2006). Continued exploration of the evolutionary diversity of algae is important to
identify species that are adept at making fuel precursors and those with high productivity
under various environmental conditions.
Choice of the number of algal model systems to study. Given the phylogenetic
diversity of microalgae, a large number of model systems could be studied. However, in a
practical sense, the number to be studied in depth should be limited because a critical
mass of researchers is required on a given species to make progress. In addition to the
requirement for making fuel precursors, other factors related to what model species to
study include ease of application of molecular and biochemical techniques, and
transgenic capabilities. Having a sequenced genomic is critical, but lack of genome
sequence at the outset should not be considered a barrier, considering that new
sequencing technologies can generate a eukaryotic genome‘s worth of data in a week. It
must be noted though, that the genomic data are only as useful as the annotation, so it
will be important to provide sufficient resources to allow for detailed analysis of the data.
Cyanobacteria
Cyanobacteria generally do not accumulate storage lipids but they can be prolific
carbohydrate and secondary metabolite producers, grow readily, and both fix atmospheric
nitrogen and produce hydrogen. Moreover, they can be genetically manipulated, making
them attractive organisms for biofuels production. A recent transgenic approach has
enabled cyanobacterial cellulose and sucrose secretion (Nobles and Brown 2008), and
previous work enabled ethanol production (Deng and Coleman 1999).
Cyanobacteria (blue-green algae) have many advantages over land plants, e.g., higher
solar conversion efficiencies, much smaller land footprint, shorter growth cycle, and the
ability to biosynthesize fuels and relevant biocatalysts. A significant advantage of
cyanobacteria over green algae is that they are much easier to manipulate genetically,
therefore allowing systematic genetic analysis and engineering of metabolic pathways.
The model cyanobacterium Synechocystis sp. PCC 6803 has the potential to become a
platform organism for the study of carbon metabolism toward production of hydrocarbon
fuels and intermediates. The genome of this strain was sequenced over a decade ago, as
the first among photosynthetic organisms. Many photosynthesis and carbon metabolism
mutants have been generated, and high-throughput analytical techniques have been
applied to the study of its transcriptome, proteome, and metabolome. However, a
comprehensive understanding of carbon metabolism and regulation is not yet available,
hindering the development of genetic engineering strategy for biofuel production.
In order to redirect carbon to a fuel production pathway, it will be necessary to remove
the normal carbon sinks, and to understand the consequences at cellular and molecular
levels. The important carbon storage compounds (sinks) in this cyanobacterium include
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