Biofilms are resilient to a wide variety of environmental stresses. This inherited robustness has been exploited mainly for bioremediation. This thesis addressed the key challenges for the use of biofilms as biocatalysts on biological as well as on technical level. On biological level the question how do catalytic biofilms react to the biologically challenging compound styrene was studied. On technical level, crucial process parameters such as substratum for biofilm growth and oxygen mass transfer have been targeted.To address the biological question, a reliable toolbox based on a modified flow-cell coupled to confocal microscopy and a GFP-marker system was established. Through a time-resolved, non-invasive and quantitative approach, Pseudomonas sp. strain VLB120?C biofilm development and its response to the toxic solvent styrene was investigated. Although Pseudomonas cells experience severe membrane damage during styrene treatment, they are able to adapt to the toxic conditions and recover. The solvent styrene did not affect the growth rate and overall biofilm structural integrity. Compared to control experiments with planktonic cells, the Pseudomonas biofilm adapted much better to toxic concentrations of styrene, as nearly 65% of biofilm cells were not permeabilized (viable), compared to only 7% in analogous planktonic cultures.