8 Marine Biotechnology
303
been completely sequenced (Bowler et al. 2008). In this species, therefore, genomic
approaches can give important insights into the biology and the biochemistry of a
high lipid producing algae.
8.4.5 Algae for Ethanol Production
An alternative approach for biofuel production is to use the photosynthetic products of cyanobacteria to produce ethanol in vivo. The feasibility of the approach
was demonstrated by Deng and Coleman (1999) who used Synechococcus sp. PCC
7942 transformed with pyruvate decarboxylase and alcohol dehydrogenase from
the bacterium Zymomonas mobilis. The transformed cyanobacterium synthesised
ethanol from photosynthetates, which diffused into the culture medium. The system is claimed to be ready for commercial scale-up and the companies Algenol
and BioFields have committed 100 million USD for the construction of a full
scale factory (www.algenolbiofuels.com). The company Algenol now also claims
that the technique has been adapted for cyanobacteria growing in seawater. This
is an interesting example of one potential future for marine genomics in which
marine organisms and “terrestrial genes” (and vice versa) are combined to produce
promising products.
8.4.6 Algae for Hydrogen Gas Production
Many cyanobacteria and some green algae contain enzymes capable of producing
hydrogen gas (Tamagnini et al. 2002, Schütz et al. 2004, Melis and Happe 2001). In
this case the photosynthetic energy is converted directly to a useful high energy fuel
without the need for extraction since the hydrogen gasses off and can be collected.
Research on green algae has so far concentrated on Chlamydomonas reinhardtii,
which has an efficient but oxygen sensitive hydrogenase (Hankamer et al. 2007).
This constraint was partially overcome by Melis et al. (2000) by cycling between a
state of active photosynthesis and an anaerobic hydrogen producing state induced by
sulphur starvation. Strains have been developed with potential for increased hydrogen production for example in a work by (Surzycki et al. 2007) or with the selection
of strains with smaller light harvesting complexes (Polle et al. 2003) or a strain with
high starch content (Kruse et al. 2005). In cyanobacteria hydrogen can be formed
as a by-product of nitrogen fixation by nitrogenase. The hydrogen is normally oxidized by an uptake hydrogenase (for reviews see Tamagnini et al. 2002, Sakurai
and Masukawa 2007). As with hydrogen production in green algae, production by
cyanobacterial is inhibited by oxygen since the nitrogenase is oxygen sensitive.
8.4.7 Algae for Biomass Fermentation
It is also possible to grow or harvest microalgae and seaweeds for fermentation of
biomass. This fermentation could be either for ethanol or for biogas. In this case it
would be important to either achieve high growth rates or to increase the fractions
303
been completely sequenced (Bowler et al. 2008). In this species, therefore, genomic
approaches can give important insights into the biology and the biochemistry of a
high lipid producing algae.
8.4.5 Algae for Ethanol Production
An alternative approach for biofuel production is to use the photosynthetic products of cyanobacteria to produce ethanol in vivo. The feasibility of the approach
was demonstrated by Deng and Coleman (1999) who used Synechococcus sp. PCC
7942 transformed with pyruvate decarboxylase and alcohol dehydrogenase from
the bacterium Zymomonas mobilis. The transformed cyanobacterium synthesised
ethanol from photosynthetates, which diffused into the culture medium. The system is claimed to be ready for commercial scale-up and the companies Algenol
and BioFields have committed 100 million USD for the construction of a full
scale factory (www.algenolbiofuels.com). The company Algenol now also claims
that the technique has been adapted for cyanobacteria growing in seawater. This
is an interesting example of one potential future for marine genomics in which
marine organisms and “terrestrial genes” (and vice versa) are combined to produce
promising products.
8.4.6 Algae for Hydrogen Gas Production
Many cyanobacteria and some green algae contain enzymes capable of producing
hydrogen gas (Tamagnini et al. 2002, Schütz et al. 2004, Melis and Happe 2001). In
this case the photosynthetic energy is converted directly to a useful high energy fuel
without the need for extraction since the hydrogen gasses off and can be collected.
Research on green algae has so far concentrated on Chlamydomonas reinhardtii,
which has an efficient but oxygen sensitive hydrogenase (Hankamer et al. 2007).
This constraint was partially overcome by Melis et al. (2000) by cycling between a
state of active photosynthesis and an anaerobic hydrogen producing state induced by
sulphur starvation. Strains have been developed with potential for increased hydrogen production for example in a work by (Surzycki et al. 2007) or with the selection
of strains with smaller light harvesting complexes (Polle et al. 2003) or a strain with
high starch content (Kruse et al. 2005). In cyanobacteria hydrogen can be formed
as a by-product of nitrogen fixation by nitrogenase. The hydrogen is normally oxidized by an uptake hydrogenase (for reviews see Tamagnini et al. 2002, Sakurai
and Masukawa 2007). As with hydrogen production in green algae, production by
cyanobacterial is inhibited by oxygen since the nitrogenase is oxygen sensitive.
8.4.7 Algae for Biomass Fermentation
It is also possible to grow or harvest microalgae and seaweeds for fermentation of
biomass. This fermentation could be either for ethanol or for biogas. In this case it
would be important to either achieve high growth rates or to increase the fractions