Journal of Applied Phycology

, Volume 24, Issue 4, pp 657–668 | Cite as

Carbon metabolism and energy conversion of Synechococcus sp. PCC 7942 under mixotrophic conditions: comparison with photoautotrophic condition

  • Riming Yan
  • Du Zhu
  • Zhibin Zhang
  • Qingui Zeng
  • Ju Chu


To investigate the carbon metabolism and energy conversion efficiency of the cyanobacterium Synechococcus sp. PCC 7942 under mixotrophic conditions, we studied its growth characteristics in mixotrophic cultures with glucose and with acetate, respectively, and further discussed the carbon metabolism and energy utilization based on metabolic flux analysis. Results showed that both glucose and acetate could enhance the growth of Synechococcus sp. PCC 7942. The metabolic flux through the glycolytic pathway, tricarboxylic acid cycle, and mitochondrial oxidative phosphorylation was affected by the two organic substrates. Additionally, the cellular composition was also modulated by glucose and acetate. Under mixotrophic conditions, glucose exerts more significant impact on the diminishment of photochemical efficiency. Although the contribution of light energy was smaller, the cell yields based on total energy in mixotrophic cultures were higher compared with that of photoautotrophic one. On the basis of chlorophyll fluorescence analysis, the actual energy conversion efficiencies based on ATP synthesis in the photoautotrophic, glucose-mixotrophic, and acetate-mixotrophic cultures were evaluated to be 4.59%, 5.86%, and 6.60%, respectively.


Synechococcus sp. PCC 7942 Mixotrophic cultivation Carbon metabolism Energy conversion Metabolic flux analysis Chlorophyll fluorescence analysis 



Stoichiometric coefficient of metabolite i in the jth reaction (−)


m × n Matrix of stoichiometric coefficient (−)


Side area of flask receiving incident light (m2)


Light energy absorbed by the biomass unit (kJ g−1 h−1)


Actual light energy for photosynthesis (kJ g−1 h−1)


Chemical energy received from organic carbon resources (kJ g−1 h−1)


Chemical energy originated from acetate (kJ g−1 h−1)


Chemical energy originated from glucose (kJ g−1 h−1)


The total absorbed energy (kJ g−1 h−1)


Incident light intensity (μmol m−2 s−1)


Effective absorption coefficient of light (m−1)


Vector of m-dimensional metabolite accumulation rate (mmol g−1 h−1)


Relative rate of ATP synthesized (mmol g−1 h−1)


Relative rate of acetate consumption (mmol g−1 h−1)


Subvector of extracellular metabolite accumulation rate (mmol g−1 h−1)


Relative rate of glucose consumption (mmol g−1 h−1)


Accumulation rate of metabolite i (mmol g−1 h−1)


Subvector of intracellular metabolite accumulation rate (mmol g−1 h−1)


Reactor radius (m)


n-Dimensional flux vector (mmol g−1 h−1)


Flux through reaction j (mmol g−1 h−1)


Cell concentration DCW (g L−1)


Yield of cell mass based on ATP generation (g mol-ATP−1)


Cell yield based on total light energy (g kJ−1)

\( \Delta G_{\text{ACE}}^{\text{o}} \)

Free energy change of acetate complete oxidation (kJ mol−1)

\( \Delta G_{\text{ATP}}^{\text{o}} \)

Free energy change of ATP hydrolysis (kJ mol−1)

\( \Delta G_{\text{GLC}}^{\text{o}} \)

Free energy change of glucose complete oxidation (kJ mol−1)


Specific growth rate (h−1)


Vector of measurement noise variance–covariance (−)


The efficiency of photosystem II photochemistry (−)


The efficiency of energy conversion on ATP synthesis (%)



This work was supported by National Natural Science Foundation (No. 20506009); Natural Science Foundation of Jiangxi province (No. 0530095); and The Education Department of Jiangxi province (No. GJJ08147). We thank the Key Lab of Protection and Utilization of Subtropic Plant Resources for expert technical assistance. Moreover, we also wish to express our thanks to the anonymous reviewers for constructive comments.


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Copyright information

© Springer Science+Business Media B.V. 2011

Authors and Affiliations

  • Riming Yan
    • 1
    • 2
  • Du Zhu
    • 1
    • 3
  • Zhibin Zhang
    • 1
  • Qingui Zeng
    • 1
  • Ju Chu
    • 2
  1. 1.Key Laboratory of Protection and Utilization of Subtropic Plant Resources of Jiangxi ProvinceJiangxi Normal UniversityNanchangChina
  2. 2.State Key Laboratory of Bioreactor EngineeringEast China University of Science and TechnologyShanghaiChina
  3. 3.Key Laboratory for Research on Active Ingredients in Natural Medicine of Jiangxi ProvinceYichun UniversityYichunChina

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