It was found (4) that the Gibbs energy dissipation required for the production of 1 C-mol biomass mainly depends on the C source used (equations 3a and 3b) The type of microorganism and the type of electron acceptor have only minor effects, as shown in Figures 5a and 5b. The influence of the C source on Y^X can be characterized by the following:

• Its number C of carbon atoms (e.g., for CO2 C = 1 and for glucose C = 6) as shown in Figure 5a

y is a stoichiometric number of a chemical compound that represents the number of electrons in the compound. For organic compounds y is per C-mol, for inorganic compounds y is per mol. For example, for CO2 y = 0, for CH4 y = 8, and for glucose y = 4. The concept of degree of reduction will be further elucidated extensively later in this article. For organic compounds (Fig. 5a), y has a value between 0 and 8. For inorganic compounds (Fig. 5b), only a lower value of 0 holds; a maximal value does not exist because there is no normalization per atom. It is relevant to know that biomass has a degree of reduction of about 4.2. Equation 3a and Figure 5a show that, in the situation that RET is not required for both hetero- and autotrophic growth, the Gibbs energy needed to produce biomass

This correlation was found to hold (with ± 40% accuracy) for a very wide variety of organisms, for different electron

• Increases if the number of C atoms in the carbon source (the parameter C in equation 3a) decreases

Figure 4. Maintenance Gibbs energy mG (in kJ/C-mol biomass h) for aerobic (a) and anaerobic (b) growth, shown as an Arrhenius function of temperature. The lines represent equation 2.


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Brew Your Own Beer

Discover How To Become Your Own Brew Master, With Brew Your Own Beer. It takes more than a recipe to make a great beer. Just using the right ingredients doesn't mean your beer will taste like it was meant to. Most of the time it’s the way a beer is made and served that makes it either an exceptional beer or one that gets dumped into the nearest flower pot.

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