Theoretische Grundlagen des Auxiliarsubstratkonzeptes und seine praktischen Konsequenzen in biotechnischen Prozessen

Raw materials for microbial synthesis of single cell protein and metabolites are chemo-heterotrophic substrates. The growth and product yields are economically very important parameters. Therefore it is necessary to look for methods to optimize these biotechnological processes, i. e. to increase these values up to the theoretically possible limits. In the SCP production the growth yield is determined energetically and in the overflow production the yield is influenced by the amount of biologically useful energy which is produced during the product synthesis. It is demonstrated that the auxiliary substrate concept is appropriate to improving the yield both for SCP- und product synthesis. In the SCP synthesis two (or more than two) substrates must be mixed that way that the biologically useful energy, which is generated along the way from substrates to a central precusor for the cell substance synthesis, becomes a maximum thus no further substrate need to be oxidized merely for the purpose of energy generation. By using a substrate, which operates only as an energy donor in the mixture the carbon metabolism determined upper limit of the carbon conversion efficiency can be attained. For with the overflow production of metabolites the biologically useful energy seems to be responsible for the discrepancy between the metabolism-determined product yield and the experimentally obtained one, the energy liberated during the production of primary metabolites must be kept low. This might be reached by using substrate mixtures. Furthermore it is shown that in this way the specific production rate can be improved as well.