Experimental Investigation and Reaction Kinetics Modeling of Biomass Formation, Substrate Consumption and Product Formation During Startup of Fixed-Bed Cultures with Immobilized Lactococcus lactis ssp. lactis

Abstract

Lactic acid bacteria (LAB) like Lactococcus lactis ssp. lactis are used in food industry as well as for prodn. of bacteriocins and optically pure lactic acid. Fixed-bed processes are highly productive but math. description is often complex. The aim of this work was to establish a mathematica model for process design. Biomass formation, lactose consumption and lactate prodn. during start-up of fixed-bed cultures with immobilized L. lactis was investigated exptl. and described by a reaction kinetics model. Appropriate modeling and simulation of fixed-bed processes require biomass data. Therefore, a low-vol. multiple fixed-bed reactor system (Multiferm) was used to investigate biomass formation of a L. lactis strain during the start-up phase of fixed-bed cultivation. The generation of data in parallel expts. was fast and easily compared to larger single reactor systems. Biomass data obtained from both fractions, retained and free suspended biomass, was used for modeling and simulation, together with data for lactose and lactate. The underlying Luedeking-Piret-like model structure was developed based on the results from suspension cultivations with the same strain. The fixed-bed system was described as perfusion culture with cell retention. For this, merely four addnl. parameters had to be defined to extend the suspension model to fixed-bed cultures. Exptl. trends and steady states of both biomass fractions besides substrate and product could be described very well. Thus, this model could be used for process layout during process development. [on SciFinder(R)]