(94d) Thermodynamic Analysis of a Microbial Cell: a Process Synthesis Approach

In this contribution, it is shown that with the right kind of data measurement, it is possible to extract vital information (from an experimental measurement) that could be used for the analysis and design of a process. Using the three process synthesis tools (mass, energy and entropy balances), thermodynamic properties such as enthalpy of formation (Hfcell) and heat production (qcell) of a bacterium cell are estimated from a chemostat experimental measurement reported by Collet et al (2004). Gibbs free energy of formation (Gfcell) and maintenance free energy (mE) of the cell are also estimated. The values of Hfcell and mE agree well with the vast amount of literature present (von Stockar et al, 2005; von Stockar and Liu,1999; Tijhuis et al, 1993; Russel,1986; Roels,1983). The values for Gfcell and qcell were not far off literature values either (von Stockar et al, 2005; Russel, 1986). The results have allowed us to be able to predict possible thermodynamically feasible reaction for a given substrate and product(s); hence setting process targets (in this case, predicting maximum hydrogen production).

Key words: thermodynamics, fermentation reactions, process targets

References

Collet, C., Adler, N., Schwitzguébel, J. P. and Péringer, P. 2004. Hydrogen Production by Clostridium thermolacticum during continuous fermentation of lactose. International Journal of Hydrogen Energy, 29, 1479 ? 1485

Russell, J. B., 1986. Heat production by ruminal bacteria in continuous culture and its relationship to maintenance energy. Journal of Bacteriology, 168, 2, 694 ? 701

Roels, J. A., 1983. Energetics and Kinetics in biotechnology. Elsevier biomedical press, Amsterdam.

Tijhuis, L., van Loosdrecht, M.C.M., Heijnen, J.J., 1993. A thermodynamically based correlation for maintenance Gibbs energy requirements in aerobic and anaerobic chomotrophic growth. Biotechnol. Bioen., 42, 509-519

von Stockar, U., Liu, J-S., 1999. Does microbial life always feed on negative entropy? Thermodynamic analysis of microbial growth. Biochem. Biophys. Acta. 1412, 191-211.

von Stockar, U., Maskow, T., Liu, J., Marison, I. W., Patiño, R., 2005. Thermodynamics of a microbial growth and metabolism: An analysis of the current situation. J. Biotechnol.,DTD 5.