(German title: Untersuchung des Prozessverhaltens von produktiven Biofilmen)

Although productive biofilms have long been used for industrial processes, such as the production of acetic acid, conventional reactor systems are still superior to biofilms as a production process. In order to better utilise biofilms industrially, a deeper understanding of the processes in a biofilm is necessary. This essentially involves understanding reaction and diffusion processes within the extracellular polymeric substance (EPS), a matrix consisting of a large number of organic compounds such as sugars, proteins, lipids and DNA. 
For this reason, this project aims to investigate the process behaviour of active biofilms using non-invasive FRAP measurements by means of confocal microscopy and to establish a link to the product yield. Based on these measurements, a mathematical model for productive biofilms in flow-through cells is to be developed, identified and validated in co-operation with the Fraunhofer ITWM. This model will describe the dependence of biofilm productivity on the nutrients supplied over time. The core of this model will be a reaction-diffusion equation system that describes the mass transport of nutrients and products between the medium and biofilm via the outer layer of the biofilm as well as the transport and metabolism within the biofilm over time. 

The CLSM will be used to determine both the biofilm density and the diffusion coefficients at certain time intervals during each experiment, the latter using a two-dimensional variant of fluorescence recovery after photobleaching (FRAP), which is also to be further developed in this project. The reaction rates (uptake rates of the nutrients and release rates of the product) cannot be measured directly and must therefore be calculated using mathematical methods. The mathematical model created in this way can be used in future as a basis for improved cultivation of biofilms and for online monitoring in the production phase.