Understanding the regulatory network of biofilm formation in Pseudomonas taiwanensis VLB120

Pseudomonas taiwanensis VLB120ΔC is a biofilm forming, solvent tolerant bacterium efficiently producing a variety of industrially attractive fine chemicals in catalytic biofilms. The primary goal of this thesis was to determine genetic targets related to biofilm formation in order to optimize the biofilm based synthesis of (S)-styrene oxide. Applying several mutagenesis approaches, more than 80 mutants were constructed that showed distinct changes in the multicellular growth format compared to the wild type. A novel quantitative assay for analyzing the biofilm formation of these mutants in a continuous flow-through system was developed. Amongst the 80 mutants, five showed a particularly interesting behavior by forming macroscopic cell aggregates in liquid culture in dependency on the carbon source. The autoaggregation was based on a substantially increased cell surface hydrophobicity caused by an altered lipopolysaccharide composition. The aggregating mutants exhibited a significantly stronger surface adhesion and enhanced biofilm formation compared to the parent strain. These characteristics proved beneficial for the synthesis of (S)-styrene oxide. Much more attached biomass was formed by the autoaggregating mutant in a capillary biofilm microreactor circumventing the initial unproductive adaptation phase of the wild type at the beginning of the process. Thereby, significantly enhanced final product concentrations and higher volumetric productivities were achieved. In conclusion, the present thesis revealed a huge number of possible genetic targets for further biofilm engineering of P. taiwanensis VLB120ΔC and demonstrated the potential of the application of hyperadherent mutants in product oriented biofilm processes.