Academic Education

Academic Career

Research Areas

• Research in my group is mainly concerned with elucidating molecular structure-function relationships and cellular modes of action of functional biopolymers, with a focus on partially acetylated chitosans. In a series of European, national and international collaborative research projects, we have analyzed the influence of the degree of polymerization (DP) and of the fraction of acetylation (F_A) of chitosans on their bioactivities, such as their antimicrobial and plant strengthening activities. We found a strong influence of F_A and, above a minimum threshold DP, a weaker influence of DP on most bioactivities. These results allowed commercial chitosan producers to optimize their production processes and to set up quality control measures so that today, ‘second generation’ chitosans with defined DP and F_A are beginning to replace the ill-defined first generation chitosan, and their reliable bioactivities are invigorating the development of chitosan-based applications e.g. in sustain­able agriculture. More recently, we have started to investigate the influence of the pattern of acetylation (PA) on bioactivities which we had predicted to be strong based on the observation of sequence-dependent chitosan hydrolases in target organisms. To this end, we have developed a strong research focus on chitin and chitosan synthesizing, modifying, and degrading enzymes (CCME). We have developed reverse mass spectro­metric fingerprinting techniques for the analysis of structure-function relationships of CCME, and bioinforma­tic as well as protein engineering tools to modify subsite preferences of these enzymes. Using well-defined recombinant enzymes and a mass spectrometric method we had developed for the quantitative sequencing of partially acetylated chitosan oligosaccharides (paCOS), we have then developed enzymatic-mass spectro­metric fingerprinting tools to analyze the F_A and PA of chitosan polymers. In collaboration with European partners, we are currently developing biotechnological production methods for chitosan oligomers and polymers with defined, non-random PA, both using in vivo production in bacterial cell factories and in vitro production using enzymatic biorefinery approaches. We are beginning to see a crucial influence of PA on the physico-chemical properties and on the biological functionalities of chitosan oligomers and polymers. We predict that this will lead to the development of ‘third generation’ designer chitosans which will offer new opportunities for chitosan applications. In parallel, we have started to intensify investigations into the occur­rence, chemical structure, and physiological roles of natural chitosans in fungal and microalgal cell walls.