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pH control in biological systems using calcium carbonate
Author(s) -
Salek S.S.,
van Turnhout A.G.,
Kleerebezem R.,
van Loosdrecht M.C.M.
Publication year - 2015
Publication title -
biotechnology and bioengineering
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.136
H-Index - 189
eISSN - 1097-0290
pISSN - 0006-3592
DOI - 10.1002/bit.25506
Subject(s) - alkalinity , chemistry , calcium carbonate , mass transfer , carbonate , chemical equilibrium , phase (matter) , reaction rate , chemical engineering , chromatography , catalysis , organic chemistry , engineering
Due to its abundance, calcium carbonate (CaCO 3 ) has high potentials as a source of alkalinity for biotechnological applications. The application of CaCO 3 in biological systems as neutralizing agent is, however, limited due to potential difficulties in controlling the pH. The objective of the present study was to determine the dominant processes that control the pH in an acid‐forming microbial process in the presence of CaCO 3 . To achieve that, a mathematical model was made with a minimum set of kinetically controlled and equilibrium reactions that was able to reproduce the experimental data of a batch fermentation experiment using finely powdered CaCO 3 . In the model, thermodynamic equilibrium was assumed for all speciation, complexation and precipitation reactions whereas, rate limited reactions were included for the biological fatty acid production, the mass transfer of CO 2 from the liquid phase to the gas phase and the convective transport of CO 2 out of the gas phase. The estimated pH‐pattern strongly resembled the measured pH, suggesting that the chosen set of kinetically controlled and equilibrium reactions were establishing the experimental pH. A detailed analysis of the reaction system with the aid of the model revealed that the pH establishment was most sensitive to four factors: the mass transfer rate of CO 2 to the gas phase, the biological acid production rate, the partial pressure of CO 2 and the Ca +2 concentration in the solution. Individual influences of these factors on the pH were investigated by extrapolating the model to a continuously stirred‐tank reactor (CSTR) case. This case study indicates how the pH of a commonly used continuous biotechnological process could be manipulated and adjusted by altering these four factors. Achieving a better insight of the processes controlling the pH of a biological system using CaCO 3 as its neutralizing agent can result in broader applications of CaCO 3 in biotechnological industries. Biotechnol. Bioeng. 2015;112: 905–913. © 2014 Wiley Periodicals, Inc.