Kinetics and Energetics of Photosynthetic Micro-Organisms in Photobioreactors
201
and because it is easier to work with experimentally measured variables, the
biotic state vector will be
X = (Cpc , Cpr , CCH , CX, CG)
and the abiotic state vector will be
Y = (CN, Cs, Cp)
The state vector is therefore
C = (Cpc , Cpr , CCH , Cx, CG, CN, CS, Cp)
where PC, Pr, CH, X, G, N, S, P denote respectively the phycocyanins, proteins,
chlorophylls, biomass, glycogen, nitrates, sulfates and phosphates. In addition,
we can define the mass biotic fraction of a component i as zi = Ci/Cx and the
total biomass as CXT = Cx + CG.
Before the appearance of the limitation by sulfur or nitrogen, the previous
experimental results indicate that the biotic mass fractions of proteins (Zpr),
phycocyanins (Zpc), and chlorophylls (ZcH) remain constant whatever the energy
flux, in exponential or linear growth phases:
Zpr = 0.63 kg Pr.kg X- 1
Zpc = 0.15 kg PC.kg X- 1
ZCH = 0.009 kg CH.kg X- 1
Some assumptions can be made here [73]:
-
the C, H, O, N, S and P elemental composition of the biomass X remains
constant; this assumption was experimentally confirmed for exponential and
linear growth phases - under mineral limiting conditions, i.e. for stationary
phases, this assumption is taken to remain valid;
-
the biotic mass fraction of proteins remains constant under nitrate and
phosphate starvation but decreases under sulphur starvation;
-
the biotic mass fraction of chlorophylls remains constant under nitrate,
sulfate, or phosphate starvation;
- the biotic mass fraction of phycocyanins decreases under nitrate and
sulfate starvation, but remains constant under phosphate starvation.
In this case, the stoichiometric equation associated with growth is given by
Eq. (30) or Eq. (31) if ionic species are considered. It should be noted that this
equation implies a constant elemental formula for biomass with 10% of
exopolysaccharide, i.e. for incident radiant energy fluxes down to 20W.m -2.
The conversion yields for nitrate, sulfate and phosphate are given by Eqs.
(33-35). For higher incident fluxes, a new single stoichiometric equation must be
constructed from different percentages of exopolysaccharide obtained by Cornet
et al. [86] in continuous cultures and confirmed by Lu [87] in batch cultures.
These results are summarized in Table 6. Such metabolic deviations with
varying incident fluxes have been also observed on other photosynthetic microorganisms [88].
201
and because it is easier to work with experimentally measured variables, the
biotic state vector will be
X = (Cpc , Cpr , CCH , CX, CG)
and the abiotic state vector will be
Y = (CN, Cs, Cp)
The state vector is therefore
C = (Cpc , Cpr , CCH , Cx, CG, CN, CS, Cp)
where PC, Pr, CH, X, G, N, S, P denote respectively the phycocyanins, proteins,
chlorophylls, biomass, glycogen, nitrates, sulfates and phosphates. In addition,
we can define the mass biotic fraction of a component i as zi = Ci/Cx and the
total biomass as CXT = Cx + CG.
Before the appearance of the limitation by sulfur or nitrogen, the previous
experimental results indicate that the biotic mass fractions of proteins (Zpr),
phycocyanins (Zpc), and chlorophylls (ZcH) remain constant whatever the energy
flux, in exponential or linear growth phases:
Zpr = 0.63 kg Pr.kg X- 1
Zpc = 0.15 kg PC.kg X- 1
ZCH = 0.009 kg CH.kg X- 1
Some assumptions can be made here [73]:
-
the C, H, O, N, S and P elemental composition of the biomass X remains
constant; this assumption was experimentally confirmed for exponential and
linear growth phases - under mineral limiting conditions, i.e. for stationary
phases, this assumption is taken to remain valid;
-
the biotic mass fraction of proteins remains constant under nitrate and
phosphate starvation but decreases under sulphur starvation;
-
the biotic mass fraction of chlorophylls remains constant under nitrate,
sulfate, or phosphate starvation;
- the biotic mass fraction of phycocyanins decreases under nitrate and
sulfate starvation, but remains constant under phosphate starvation.
In this case, the stoichiometric equation associated with growth is given by
Eq. (30) or Eq. (31) if ionic species are considered. It should be noted that this
equation implies a constant elemental formula for biomass with 10% of
exopolysaccharide, i.e. for incident radiant energy fluxes down to 20W.m -2.
The conversion yields for nitrate, sulfate and phosphate are given by Eqs.
(33-35). For higher incident fluxes, a new single stoichiometric equation must be
constructed from different percentages of exopolysaccharide obtained by Cornet
et al. [86] in continuous cultures and confirmed by Lu [87] in batch cultures.
These results are summarized in Table 6. Such metabolic deviations with
varying incident fluxes have been also observed on other photosynthetic microorganisms [88].