Introduction

The growth of microorganisms occurs within a wide range of pHs and temperatures, and on a wide variety of nutrients. Figure 1 shows a typical batch experiment where a substrate (starting at concentration Cso) is converted by a microorganism (Cxo at t = 0). The microorganism grows exponentially at a specific growth rate imax and with yield Y DmX. After depletion of the substrate, which is characterized by the substrate affinity constant Ks and a threshold concentration, the biomass concentration reaches Cx = Cxo + ymXCso. Subsequently the biomass concentration decreases due to maintenance and/or biomass decay, which is characterized by the maintenance coefficient mD (or the decay coefficient kd). The relevant substrate always acts as electron donor, and therefore it is proper to define the biomass yield and maintenance on donor (D).

In the design of processes with growing microorganisms (fermentation processes and biological waste-treatment processes) the key parameters that need to be considered are the maximal biomass yield on substrate (y§X) , the substrate maintenance coefficient mD, the maximal growth rate (umax), and the substrate affinity constant (Ks). These four key parameters are sufficient to describe growth of

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Brew Your Own Beer

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