Targeted Metabolomics for Strain and Bioprocess Development for Heterologous Microbial Monolignol and Lignan Synthesis

Metabolites of the monolignol and lignan pathway are promising plant natural products for the prevention and treatment of lifestyle-related diseases. Heterologous microbial production of these metabolites offers the potential for a more stable and sustainable supply, but more research regarding strain and process development is necessary. In the first part of this thesis, a targeted metabolomics method for the quantification of extra- and intracellular monolignol and lignan metabolites was developed. Comparing multiple extraction methods showed that hot water cell disruption is best suited regarding extraction efficacy from Escherichia coli and stability of these metabolites. A novel separation method enabling quantification of 17 monolignol and lignan metabolites was established. The use and applicability of the targeted metabolomics method were demonstrated by comparing enzymes to alleviate metabolic bottlenecks and by monitoring metabolite titers over time during cultivation of recombinant E. coli. In the second part of this thesis, the first stirred-tank reactor (STR) process for the biotransformation of coniferyl alcohol to secoisolariciresinol was set up with recombinant E. coli. After preliminary experiments in shake flasks, the batch process was transferred to an STR, and the impact of various process parameters was investigated. Via targeted metabolomics, the lignan pathway activity was monitored, demonstrating two phases of maximum intracellular lignan accumulation. The supplemented copper concentration and the substrate feeding strategy had remarkable influence on the production of lignans. The results emphasize the need for improved pinoresinol formation. This thesis facilitates future studies concerned with the microbial production of monolignol and lignan metabolites by providing a targeted metabolomics method. It indicates strain optimization targets and sets a basis for future bioprocess development and scale-up studies.