Modellbasierte Prozessführung zur Kultivierung des Bakteriums Photorhabdus luminescens
Nematodes (Heterorhabditis bacteriophora) are successfully used in pest control of soil-borne insects. A substantial cost reduction in the production of nematodes is a prerequisite for vast application. The industrial production process starts with a pre-culture of their symbiotic bacterium (Photorhabdus luminescens). The conditions in that pre-culture are very decisive for the development of the nematodes. Model-based control strategies for cultivation of the bacteria are presented, which guarantee reproducible growth conditions. Based upon a system of non-linear differential equations, the dynamics of bacterial growth were described. One application shown is the implementation of a non-linear estimation method. This allows an online estimation of all relevant process variables. Using concepts and ideas from the theory of differentially flat systems, one can calculate substrate feed rates and design closed loop trajectory controllers. As concrete example, fed batch cultivations at lab-scale are presented. These show, that the application of model-based control leads to a reproducible bacterial growth with high cell densities.