80–247 μM (Badger and Bek 2008). Non-carboxysomal form I Rubisco has higher
affinities for CO 2 and its KCO 2 values in the range of 6–138 μM (Badger and Bek
2008), while those packaged into carboxysomes, have KCO 2 values in the range of
72–250 μM; 6, 65, 69, 84, 92 (Scott et al. 2007; Badger and Bek 2008; Gibson and
Tabita 1977).
11.5 Metabolic Product of CO2 Sequestration
Hydrocarbons and triacylglycerol are the major metabolic products of CO 2 sequestration in bacteria fungi, algae, higher plants, and animals. Alkane production occurs
by decarboxylation of fatty aldehydes. It occurs in a three step process using
different enzyme: (1) fatty acid elongase elongates hexadecanoic acid to an evencarbon number fatty acid; (2) fatty acid reductase reduces the fatty acids to
aldehydes; and (3), Aldehyde decarbonylase decarbonylates the aldehydes to yield
alkanes (Metzger et al. 1985; Banerjee et al. 2002). It has been reported that
odd-carbon number alkanes are found in a large proportion as compared to evencarbon number alkanes in higher plants while they contain even-carbon number fatty
acids as the major fatty acid components. In contrast, in some bacteria, similar levels
of even and odd-carbon number alkanes have been reported, where even-carbon
number fatty acids were predominant inside bacteria. As the decarbonylation pathway does not adequately explain these facts, we are forced to consider that an
alternative alkane synthesis pathway may exist in the bacteria.
The fuel oils are comprised of the aliphatic alkanes (paraffins) and cycloalkanes
(naphthenes), aromatics (e.g., benzene) and olefins (e.g., styrene and indene compose 10–20% and 1%, respectively, of the fuel oils (Park et al. 2005). Less than 5%
of fuel oil consists of polycyclic aromatic hydrocarbons.
Triacylglycerols (TAG) are fatty acid trimesters of glycerol. There are different
types of TAG depending on their fatty acid composition. Biosynthesis and accumulation of TAG occur in a group of organisms belonging to the actinomycetes, such as
Streptomyces, Rhodococcus, Mycobacterium, Dietzia or Gordonia (Alvarez et al.
2002).
11.6 Biodiesel
Biodiesel is produced from renewable resources such as oil bearing plants, micro,
and macro algae. It is a mixture of Fatty Acid Methyl Esters (FAMEs). Due to the
shortage of the available energy resources and increase in environmental pressure on
green house gases, have been forced to discover some alternative method for
renewable energy sources. Biodiesel does not contribute to extra atmospheric CO 2
emissions as it is biogenic (Demirbas 2008). It reduces production of soot, sulfur,
unburned hydrocarbon, and polycyclic aromatic hydrocarbon emissions as compared to petroleum diesel (Aresta et al. 2005; Demirbas 2008). It can be applied in
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R. K. Bharti et al.
affinities for CO 2 and its KCO 2 values in the range of 6–138 μM (Badger and Bek
2008), while those packaged into carboxysomes, have KCO 2 values in the range of
72–250 μM; 6, 65, 69, 84, 92 (Scott et al. 2007; Badger and Bek 2008; Gibson and
Tabita 1977).
11.5 Metabolic Product of CO2 Sequestration
Hydrocarbons and triacylglycerol are the major metabolic products of CO 2 sequestration in bacteria fungi, algae, higher plants, and animals. Alkane production occurs
by decarboxylation of fatty aldehydes. It occurs in a three step process using
different enzyme: (1) fatty acid elongase elongates hexadecanoic acid to an evencarbon number fatty acid; (2) fatty acid reductase reduces the fatty acids to
aldehydes; and (3), Aldehyde decarbonylase decarbonylates the aldehydes to yield
alkanes (Metzger et al. 1985; Banerjee et al. 2002). It has been reported that
odd-carbon number alkanes are found in a large proportion as compared to evencarbon number alkanes in higher plants while they contain even-carbon number fatty
acids as the major fatty acid components. In contrast, in some bacteria, similar levels
of even and odd-carbon number alkanes have been reported, where even-carbon
number fatty acids were predominant inside bacteria. As the decarbonylation pathway does not adequately explain these facts, we are forced to consider that an
alternative alkane synthesis pathway may exist in the bacteria.
The fuel oils are comprised of the aliphatic alkanes (paraffins) and cycloalkanes
(naphthenes), aromatics (e.g., benzene) and olefins (e.g., styrene and indene compose 10–20% and 1%, respectively, of the fuel oils (Park et al. 2005). Less than 5%
of fuel oil consists of polycyclic aromatic hydrocarbons.
Triacylglycerols (TAG) are fatty acid trimesters of glycerol. There are different
types of TAG depending on their fatty acid composition. Biosynthesis and accumulation of TAG occur in a group of organisms belonging to the actinomycetes, such as
Streptomyces, Rhodococcus, Mycobacterium, Dietzia or Gordonia (Alvarez et al.
2002).
11.6 Biodiesel
Biodiesel is produced from renewable resources such as oil bearing plants, micro,
and macro algae. It is a mixture of Fatty Acid Methyl Esters (FAMEs). Due to the
shortage of the available energy resources and increase in environmental pressure on
green house gases, have been forced to discover some alternative method for
renewable energy sources. Biodiesel does not contribute to extra atmospheric CO 2
emissions as it is biogenic (Demirbas 2008). It reduces production of soot, sulfur,
unburned hydrocarbon, and polycyclic aromatic hydrocarbon emissions as compared to petroleum diesel (Aresta et al. 2005; Demirbas 2008). It can be applied in
246
R. K. Bharti et al.