Calorimetry and thermodynamic aspects of heterotrophic, mixotrophic, and phototrophic growth

Ian William Marison, Urs von Stockar
2011
Article

Résumé

A simple stoichiometric model is proposed linking the biomass yield to the enthalpy and Gibbs energy changes in chemo-heterotrophic, mixotrophic, and photo-autotrophic microbial growth. A comparison with calorimetric experiments on the algae Chlorella vulgaris and Chlorella sorokiniana confirmed the trends but revealed large calorimetric measurement inaccuracies. The calorimetric data on purely photo-autotrophic growth was, however, in fair agreement with calculations. The thermodynamic characteristics of photosynthetic growth, including an estimation of the Gibbs energy dissipation, are compared with similar data for chemotrophic microbes. © Akadémiai Kiadó, Budapest, Hungary 2011.

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https://infoscience.epfl.ch/record/174432?ln=fr

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Calorimetry and thermodynamic aspects of heterotrophic, mixotrophic, and phototrophic growth

Ian William Marison, Urs von Stockar

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Can microbial growth yield be estimated using simple thermodynamic analogies to technical processes?

Urs von Stockar

In view of the prime importance of the biomass yield in microbial growth for research, for environmental and for industrial applications some thermodynamic concepts are reviewed that were developed over the years in order to understand the large variations observed in this parameter and to predict it. Special emphasis is given to a comparison between cellular growth and an energy transducer, which uses an input of chemical or mechanical energy to drive a useful output reaction. It turns out that it is impossible to calculate energetic efficiencies and to predict biomass yield based on correlations of the latter because the very concept is plagued with internal inconsistencies. Nevertheless, the energy transducer model reflects at least qualitatively the compromise between two extreme types of metabolism that must have emerged during evolution. On one hand, one can imagine that microbial metabolism could dissipate most of the Gibbs energy contained in the substrates for generating large driving forces and thus fast metabolism, but this would result in small biomass yields. On the other hand, metabolism could maximize biomass yield but this would minimize the chemical driving forces and thus the growth rate. It appears that a certain range of values of Gibbs energy dissipation somewhere between these two extremes may have emerged during evolution. Correlations for estimating this range of Gibbs energy dissipation for specific microbial growth system have been developed. Based on a Gibbs energy balance, the wide variety of growth yields occurring in nature may be explained and roughly predicted. (C) 2007 Elsevier B.V. All rights reserved.

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