pH control as an indicator of the microalgae culture density (model on the example of Arthrospira platensis)

R.P. Trenkenshu

 A.O. Kovalevsky Institute of Biology of the Southern Seas the Russian Academy of RAS, 2 Nakhimov ave., Sevastopol, Russian Federation


DOI: 10.33075/2220-5861-2023-1-46-52

UDC 579.017.8:57.036                                                                                            


   The article focuses on the possibility of assessing the density of microalgae cultures by the pH value, which depends on the concentration and forms of nutrients necessary for cell growth. The simulation is based on the mechanism of carbon assimilation by the cells of the cyanobacterium Arthrospira platensis (spirulina), which is usually grown on the nutrient medium Zarrouk, containing 16 g/l NaHC03 at pH > 8.2.  Spirulina under photoautotrophic growth conditions assimilates carbon with the participation of cellular carbonic anhydrase, which converts one molecule of НСО3̅ into CO2 and OH ̅.  CO2 in the Calvin cycle is consumed for the biomass synthesis and ensures the culture growth. OH ̅ remains in the medium and while interacting with another molecule of НСО3̅ forms CO3 ̅ ̅. That is, the biomass synthesis is accompanied by the assimilation of one carbon molecule and the transfer of another molecule into a form nonabsorbed by cells, with an increase in the culture pH. Using the calculation results in silico (according to the ratio of various forms of carbon in solutions at different pH in the form of diagrams), a semi-empirical equation for the relationship of carbon forms available for assimilation by microalgae cells with the pH of the medium is proposed. The equation broadly describes the data from the diagrams published in the literature and enables to find the proportion of carbon absorbed by the cells on the basis of the balance. Given that the biomass of most microalgae species, expressed in absolute dry weight, contains 50% of carbon, the biomass concentration can be expressed in terms of the carbon content in the cells by pH value of the culture. The application of the model to describe experimental spirulina density data by pH value showed a good correspondence in a wide pH range (determination coefficient of 0.98).

Keywords: microalgae, cultivation, density, pH, carbon assimilation, modeling, Arthrospira.

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  1. Richmond A. Handbook of microalgal mass culture. Boca Raton: CRC Press, 1986, 528 p.
  2. 2. Vladimirova M.G. and Semenenko V.E. Intensivnaya kul`tura odnokletochny`x vodoroslej (Intensive culture of unicellular algae). M: AN SSSR, 1962, 60 p.
  3. Gevorgiz R.G., Alisievich A.V., and Shmatok M.G. Ocenka biomassy` Spirulina platensis (Nordst.) Geitl. po opticheskoj plotnosti kul`tur (Estimation of the biomass of Spirulina platensis (Nordst.) Geitl. by optical density of cultures). Ekologiya morya, 2005, Vol. 70, pp. 96–106.
  4. Gulin A. S. and Trenkenshu R. P. Model` konstrukcii mikrovodoroslevoj fotometricheskoj yachejki (Design model of a microalgae photometric cell). Sistemy kontrolya okruzhayushhej sredy, 2021, No.1 (43), pp. 79–86. 2220-5861-2021-1-79-865.
  5. Gabrielyan D.A., Gabel B.V., Sinetova M.A., Gabrielian A.K., Markelova A.G., Shcherbakova N.V., and Los D.A. Optimization of CO2 Supply for the Intensive Cultivation of Chlorella sorokiniana IPPAS C-1 in the Laboratory and Pilot-Scale Flat-Panel Photobioreactors. Life, 2022, 12, 1469. https:// life12101469.
  6. Ifrim G.A., Titica M., Horincar G., Antache A., Baicu L., Barbu M., and Guzmán J.L. Model Based Optimal Control of the Photosynthetic Growth of Microalgae in a Batch Photobioreactor. Energies 2022, 15, 6535.
  7. Pencheva D., Rumenkina M., Al-Djasem A., Iliev M., Karamihov V., Genova-Kalou P., and Kantardj T. pH in cell biology, microbiology and biotechnology. 2013, pp. 23–29.
  8. Adamberg K., Valgepea K., and Vilu R. Advanced continuous cultivation methods for systems microbiology. Microbiology 2015, Vol. 161, pp. 1707–1719. DOI 10. 1099/mic.0.000146.
  9. Wonshak A. Outdoor Mass Production of Spirulina: The Basic Concept. Spirulina platensis (Arthrospira): Physiology, Cell-biology and Biotechnology. London: Taylor & Francis, 1997, pp. 79–101.
  10. Zarrouk C. Contribution à l’étude d’une cyanophycée. Influence de divers facteurs physiques et chimiques sur la croissance et la photosyntèse de Spirulina maxima (Stech. Et Gardner). Geitler. Paris, 1966, 138 p.
  11. Kamennaya N.A, Ahn S.E, Park H., Bartal R., Sasaki K.A., Holman H.Y., and Jansson C. Installing extra bicarbonate transporters in the cyanobacterium Synechocystis sp. PCC6803. Enhances biomass production. Metabolic Engineering, 2015, Vol. 29, pp. 76–89.
  12. Badger M.R. and Price G.D. CO2-concentrating mechanisms in cyanobacteria: molecular components, their diversity and evolution. Journal of Experimental Botany, 2003, Vol. 54, No. 383, pp. 609–622.
  13. Price G.D., Badger M.R., Woodger F.J., and Long B.M. Advances in understanding the cyanobacterial CO2-concentrating-mechanism (CCM): functional components, Ci transporters, diversity, genetic regulation and prospects or engineering into plants. Journal of Experimental Botany, 2008, Vol. 59, No. 7, pp. 144–1461.
  14. Lelekov A.S. and Gevorgiz R.G. Modelirovanie dinamiki rosta Arthrospira (Spirulina) platensis i rN sredy` v zakry`toj po uglerodu sisteme (Modeling of growth dynamics of Arthro-spira (Spirulina) platensis and medium pH in a carbon-closed system). Voprosy sovremennoj al`gologii, 2017, No. 1 (13), URL:
  15. Drobeczkaya I.V., Minyuk G.S., Trenkenshu R.P., and Vyalova O.Yu. Rostovy`e i bioximicheskie xarakteristiki Spirulina platensis (Nordst.) Geitler pri razlichny`x usloviyax mineral`nogo pitaniya (Growth and biochemical characteristics of Spirulina (Arthrospira) Platensis (Nordst.) Geitler under various conditions of nitrogen nutrition). Ekologiya morya, 2001, Vol. 56, pp. 41–46.
  16. Guiry M.D. and Guiry G.M. Arthrospira platensis Gomont, 1892. on 2022-10-13.
  17. Schwarzenbach G. and Meier J. Formation and investigation of unstable protonation and deprotonation products of complexes in aqueous solution. J. Irtorg. Nuclear Chem. 1958 8, pp. 302–312.
  18. Gutz I. G. R. (2012). CurTiPot – pH and Acid-base Titration Curves: Analysis and Simulation Software, Version 3.6.1 [Online]. Available at: http:// www2. gutz/ Curtipot. html [accessed 16 Dec 2012 2013].
  19. Pedersen O., Colmer T.D., and Sand-Jensen K. Underwater photosynthesis of submerged plants – recent advances and methods. Plant_Physiology, 2013, Vol. 4, pp. 1–19. DOI: 10.3389/fpls.2013.00140.
  20. Lim Y.A., Chong M.N., and Foo S.C. Ilankoon IMSK. Analysis of direct and indirect quantification methods of CO2 fixation via microalgae cultivation in photobioreactors: a critical review. Renew Sustain Energy Rev 2021; 137:110579.