PhD ceremony: Mr. S.S. Weber, 16.15 uur, Academiegebouw, Broerstraat 5, Groningen
Dissertation: Engineering of penicillium chrysogenum for enhanced B-lactam biosynthesis
Promotor(s): prof. A.J.M. Driessen
Faculty: Mathematics and Natural Sciences
Enhancement of the industrial production of β-lactam antibiotics by Penicillium chrysogenum has been mainly the result of successive cycles of classical strain improvement. The research project of Stefan Weber aimed to gain more insight in the results of the classical strain improvement process, in particular on the transport processes involved in the production of β-lactam antibiotics. He improved and designed methods to construct gene deletion mutants in P. chrysogenum and GFP fusion proteins for functional analysis and subcellular localization. Analysis of all ABC transporters present in P. chrysogenum showed that ABC40 is dramatically upregulated in the presence of phenylacetic acid, the sidechain precursor for penicillin G. A detailed study showed that ABC40 functions as an ATP-dependent extrusion system for weak acids. Another attempt to identify transporters involved in β-lactam production, using a transcriptome analysis with phenoxyacetic acid, the sidechain precursor of penicillin V, resulted in 7 transporter genes that responded sufficiently significant for a more in depth analysis. From the candidate genes, 6 could be inactivated, but this did not result in a major phenotype. The introduction of additional copies of the genes coding for isopenicillin N acyltransferase (IAT) into the genome of P. chrysogenum showed that the overexpression of the gene encoding IAT relative to the other genes involved in biosynthesis resulted in a significant increase in penicillin V production.
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