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J.-F. Cornet et al.
biomass is composed of 10% exopolysaccharide and 90% active biomass. These
values have already been used to establish the stoichiometric equation for the
synthesis of total biomass under such incident flux conditions (Eqs. 27 and 30).
For such conditions, the P/2e- value is equal to 1.27 (Table 2) which is in fairly
good agreement with the theoretical value of 1.21 obtained in strict light energy
limitation conditions.
If the incident light energy flux is increased up to 300 W.m - 2, experimental
results show that the proportion of exopolysaccharide produced is sharply
increased, corresponding to an increase in the P/2e- ratio which can be
interpreted as a progressive removal of the light energy limitation. In the
extreme case, the synthesis of the exopolysaccharide only corresponds to
P/2e- = 1.73 (Table 2), compared to the theoretical value for non limitation
conditions of 1.71.
6.1.3.2 Nitrogen and Mineral Limitations
The experimental results presented in Sect. 4 indicate that biomass formed is
composed of 92 wt% of carbohydrates (glycogen and sulfated exopolysaccharides) and 8 wt% of lipids considering that the constitutive proteins are synthesized from the amino-acids produced by the breakdown of the phycocyanins.
The resulting stoichiometric equation for nitrate limited growth is written as
follows:
CO2 + 2.236H20 + 0.015H2SO4 + 3.435ATP + 2.012(NADPH, H +)
--~ CHt.65500.86080.015 + 3.435(ADP + Pi) + 2.012NADP + (154)
The corresponding P/2e- value is thus 3.435/2.012 = 1.71, which is identical
to the theoretical value obtained for non-limited light transfer conditions for the
coupling between photophosphorylation and NADP + reduction. This means
that a severe limitation by nitrogen nutrient in batch cultures may overcome the
influence of the light energy transfer limitation and impose new regulation rules
for the metabolism, i.e. towards an orientation of more ATP and less reducing
power productions. This switch of the metabolism towards non-light energy
transfer conditions can be macroscopically confirmed by the phycocyanin consumption indicating less need for antenna and light energy conversion devices.
6.1.3.3 Carbonate Limitation
The carbonate limitation induces, as expected, an inhibition of exopolysaccharide synthesis and an improvement of phycocyanins synthesis. The resulting
P/2e- calculated from the stoichiometric equation (Eq. 25) is equal to 1.23
corresponding to strict light energy transfer conditions. In this case, the limited
availability of COz at a fixed rate imposes a fixed ATP production rate
JATP whatever the light energy flux. This in turn produces the same effect as
a light energy transfer rate, i.e. the lowest P/2e- obtainable equal to 1.21.
J.-F. Cornet et al.
biomass is composed of 10% exopolysaccharide and 90% active biomass. These
values have already been used to establish the stoichiometric equation for the
synthesis of total biomass under such incident flux conditions (Eqs. 27 and 30).
For such conditions, the P/2e- value is equal to 1.27 (Table 2) which is in fairly
good agreement with the theoretical value of 1.21 obtained in strict light energy
limitation conditions.
If the incident light energy flux is increased up to 300 W.m - 2, experimental
results show that the proportion of exopolysaccharide produced is sharply
increased, corresponding to an increase in the P/2e- ratio which can be
interpreted as a progressive removal of the light energy limitation. In the
extreme case, the synthesis of the exopolysaccharide only corresponds to
P/2e- = 1.73 (Table 2), compared to the theoretical value for non limitation
conditions of 1.71.
6.1.3.2 Nitrogen and Mineral Limitations
The experimental results presented in Sect. 4 indicate that biomass formed is
composed of 92 wt% of carbohydrates (glycogen and sulfated exopolysaccharides) and 8 wt% of lipids considering that the constitutive proteins are synthesized from the amino-acids produced by the breakdown of the phycocyanins.
The resulting stoichiometric equation for nitrate limited growth is written as
follows:
CO2 + 2.236H20 + 0.015H2SO4 + 3.435ATP + 2.012(NADPH, H +)
--~ CHt.65500.86080.015 + 3.435(ADP + Pi) + 2.012NADP + (154)
The corresponding P/2e- value is thus 3.435/2.012 = 1.71, which is identical
to the theoretical value obtained for non-limited light transfer conditions for the
coupling between photophosphorylation and NADP + reduction. This means
that a severe limitation by nitrogen nutrient in batch cultures may overcome the
influence of the light energy transfer limitation and impose new regulation rules
for the metabolism, i.e. towards an orientation of more ATP and less reducing
power productions. This switch of the metabolism towards non-light energy
transfer conditions can be macroscopically confirmed by the phycocyanin consumption indicating less need for antenna and light energy conversion devices.
6.1.3.3 Carbonate Limitation
The carbonate limitation induces, as expected, an inhibition of exopolysaccharide synthesis and an improvement of phycocyanins synthesis. The resulting
P/2e- calculated from the stoichiometric equation (Eq. 25) is equal to 1.23
corresponding to strict light energy transfer conditions. In this case, the limited
availability of COz at a fixed rate imposes a fixed ATP production rate
JATP whatever the light energy flux. This in turn produces the same effect as
a light energy transfer rate, i.e. the lowest P/2e- obtainable equal to 1.21.