Heat Production in Fermentation Processes

Heat production represents one of the significant macroscopic process variables (see Fig. 2.3). Experimentally, heat evolution can be determined with the aid of measurements of temperature changes in the reactor and the volumetric heat [J/1] estimated according to the Uhlich approximation (see Equ. 3.70). An interpretation of the kinetic term dh /dtX in Equ. 3.69 is directly related 

A simplified equation is possible for the rate of heat formation for aerobic 

This procedure for estimating heat evolution is simpler than the previous method. The proportionality constant (1/To h,) for this correlation is independent of fi, slightly dependent on the substrate, and possibly dependent on the type of organism growth. This property of the constant (I/Tqih,) which is thought to be identical with the reaction enthalpy of fermentation, [MJ/mol O2] related to oxygen consumption. 

385 to 0.494 MJ/mole for filamentous fungi and from 0.385 to 0.565 MJ/mole for bacteria (Luong and Volesky, 1980), following the descending order bacteria, yeast, mold. 

As mentioned previously (Sect. 3.3) in connection with the rate of heat transport, the reaction enthalpy AH or AH is given in units of [kcal/gX] or [kcal/gS] for practical reasons. Table 5.3 summarizes AH for fermentations (Bronn, 1971). A systematic treatment is possible using classifications of aerobic and anaerobic processing versus substrate the numerical values are independent of the strain of microorganism. 

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