Mutational impact of classical strain improvement on Penicillium chrysogenum

We have examined the impact of mutations introduced into P. chrysogenum during CSI in amino acid metabolism, and the resultsshows that many of the mutations served to inactive competing biosynthesispathway to optimize the precursor flux towards cysteine biosynthesis. Inaddition, the work shows that other mutations in metabolism in a subtler mannercontributed to optimized penicillin production, whereas some mutations had noeffect, likely reflecting side effects of the rather harsh way the mutations wereinduced during the CSI programme. Here in this thesis, a number of genes werestudied and their functions were identified. However, many other genes obtainedmutations and their functions still remain unknown. Along with the genome sequencingtechniques, the advent of novel genome editing system, namely CRISPR/Cas9 technology provides a powerful tool for unravelling the exact gene andpathway functions of interest. This can be approached by deleting certain genesand observing the changes and effects on phenotypes. Of interest would be theremoval of the direct sulfhydrylation pathway by deleting the Pc22g16570 geneencoding for the enzyme catalyzing the first-step reaction. This will contributeto a better understanding of the role of the two pathways for cysteine biosynthesisin P. chrysogenum. This should be combined with techniques of monitoring thelevels of intracellular and extracellular metabolites. By use of these technologies,the underlying mechanism of classical strain improvement on P. chrysogenumstrains for enhanced penicillin production will be revealed at an unprecedenteddetail and also will give guidance for increasing the titers of valuable secondarymetabolites in cells in a rational manner.

Dissertation: http://hdl.handle.net/11370/6f9b54f2-9506-46d6-9ea7-ef80eeae83c6