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J.-F. Cornet et al.
chemical energy consumption or production as ATP taking all triphosphate
nucleotides to be equivalent and assuming that one monophosphate nucleotide
production is equivalent to the production of two ADPs. A more refined
technique would consider each metabolic reaction step separately leading to
a large number of stoichiometries to be considered and a large number of
metabolic intermediates that would have to be assumed at pseudo-steady state.
This approach implies calculating all metabolic fluxes and lies outside the scope
of this analysis.
Therefore, the biochemically structured model presented here involves four
rates (JxA), (JEPs), (Jcov) and (JATP)" The analysis of biochemical pathways,
still simplified, leads to two structuring relations (Eqs. 127 and 128). Two
relations remain to be established considering the light energy availability in
order to express a kinetic model for active biomass and exopolysaccharide
synthesis. Knowing that cofactor synthesis rate (JcoF) and ATP production
rate (JATP) are intimately linked to light energy transfer for photosynthetic
micro-organisms, this calls for a deeper analysis of the kinetics of photosynthesis
and photophosphorylations. Such an approach affords a better understanding
of the light energy limitation than an empirical evaluation of the exopolysaccaharide yield (JEPs)/(JxA) and provides clues to a correct formulation of
kinetic models for photosynthetic micro-organisms.
6.1.2 Bioenergetic Analysis of Coupling Photophosphorylations
and Photosynthesis
A detailed description of metabolism provides valuable relations between the
exopolysaccharide and active biomass production rates and the rates of the
intracellular turn over of chemical energy and reducing power carriers. The
basic idea here is to add a thorough description of the energy transducing
process in order to assess the ratio (JATP)/(Jcov) which is termed the P/2eratio.
6.1.2.1 Mechanistic and Biochemical Analysis
The central feature of photosynthesis is the conversion of light energy into redox
energy, meaning that photon capture causes a component to change its redox
potential from being moderately electropositive to being highly electronegative.
The electrons released from this component serve to generate an electrochemical
gradient, flowing through either a cyclic pathway back to rereduce the original
component, or a non-cyclic pathway to reduce additional electron acceptors, i.e.
NADP + in the case of thylakoid membranes [10]. In the non-cyclic pathway,
electrons are extracted from water, pass through a proton-translocating-electron transfer chain and then a second reaction centre and are ultimately donated
to NADP +. The production of ATP involves a proton circuit that is closely
analogous to the electron transport chain for respiration.
/
J.-F. Cornet et al.
chemical energy consumption or production as ATP taking all triphosphate
nucleotides to be equivalent and assuming that one monophosphate nucleotide
production is equivalent to the production of two ADPs. A more refined
technique would consider each metabolic reaction step separately leading to
a large number of stoichiometries to be considered and a large number of
metabolic intermediates that would have to be assumed at pseudo-steady state.
This approach implies calculating all metabolic fluxes and lies outside the scope
of this analysis.
Therefore, the biochemically structured model presented here involves four
rates (JxA), (JEPs), (Jcov) and (JATP)" The analysis of biochemical pathways,
still simplified, leads to two structuring relations (Eqs. 127 and 128). Two
relations remain to be established considering the light energy availability in
order to express a kinetic model for active biomass and exopolysaccharide
synthesis. Knowing that cofactor synthesis rate (JcoF) and ATP production
rate (JATP) are intimately linked to light energy transfer for photosynthetic
micro-organisms, this calls for a deeper analysis of the kinetics of photosynthesis
and photophosphorylations. Such an approach affords a better understanding
of the light energy limitation than an empirical evaluation of the exopolysaccaharide yield (JEPs)/(JxA) and provides clues to a correct formulation of
kinetic models for photosynthetic micro-organisms.
6.1.2 Bioenergetic Analysis of Coupling Photophosphorylations
and Photosynthesis
A detailed description of metabolism provides valuable relations between the
exopolysaccharide and active biomass production rates and the rates of the
intracellular turn over of chemical energy and reducing power carriers. The
basic idea here is to add a thorough description of the energy transducing
process in order to assess the ratio (JATP)/(Jcov) which is termed the P/2eratio.
6.1.2.1 Mechanistic and Biochemical Analysis
The central feature of photosynthesis is the conversion of light energy into redox
energy, meaning that photon capture causes a component to change its redox
potential from being moderately electropositive to being highly electronegative.
The electrons released from this component serve to generate an electrochemical
gradient, flowing through either a cyclic pathway back to rereduce the original
component, or a non-cyclic pathway to reduce additional electron acceptors, i.e.
NADP + in the case of thylakoid membranes [10]. In the non-cyclic pathway,
electrons are extracted from water, pass through a proton-translocating-electron transfer chain and then a second reaction centre and are ultimately donated
to NADP +. The production of ATP involves a proton circuit that is closely
analogous to the electron transport chain for respiration.
/