Pseudomonas and Beyond: Polyamine metabolism, lignin degradation and potential applications in industrial biotechnology

Renewable resources such as lignocellulosic biomass are promising feedstocks for the production of bio-fuels and value-added products. Biocatalysts are considered important tools in such processes. Pseudomonas putida S12 has a broad metabolic potential and is exceptionally tolerant towards a range of toxic organic solvents and aromatic compounds, which makes this bacterium a very suitable host for the production of aromatic compounds. The work described in this thesis provides insights into the metabolism of the polyamine putrescine in P. putida S12, which presumably plays a role in the response to solvent stress. The utilisation of lignocellulosic biomass as a renewable feedstock for sustainable energy and chemicals production, is gaining increased attention. Still, intensive research is required to enable efficient utilisation of all components contained within lignocellulose, and to expand the range of value-added products to be obtained from this resource. In this study, novel bacterial isolates have been investigated that could potentially serve as a source of lignin degrading enzymes. Application of such enzymes combined with the solvent tolerance of P. putida S12 could open up a new avenue for the valorization of the ubiquitously available renewable resource lignin. It has also been made clear, however, that the recalcitrant nature and complex structure of lignin greatly complicates the research into biological lignin depolymerization. Much is to be learned and possibly gained from bacterial lignin degradation, which justifies more and intensified research