The influence of strain improvement and genetic modification on the pattern of secondary metabolites in industrial strains of Penicillium chrysogenum and Aspergillus niger.

July 2002

Lecture at the 10th IUMS (International Union of Mycological Societies) Congres in Paris, France (27 July - 1 August 2002)

By Piet W.M. van Dijck, Henk Spierenburg, Jens C. Frisvad and Rob A. Samson
DSM Food Specialties, Delft, The Netherlands, Bio-Centrum DTU, Techn. Univ. Denmark, Lyngby, Denmark and Centraalbureau voor Schimmelcultures (CBS), Utrecht, The Netherlands

Multiple rounds of mutation and selection markedly may change the phenotypic appearance of an industrial strain. And this up to the point that with classical taxonomy it becomes difficult to identify a strain as belonging to the same species as the original strain due to the loss/change of essential identification parameters. However, strain identification is an important parameter in the regulatory process of the approval of products made through biotechnology.
In this research the pattern of secondary metabolites produced by strains from a safe industrial strain lineage of Penicillium chrysogenum or Aspergillus niger, when cultivated under growth conditions optimal for the formation of secondary metabolites, has been studied. Strains were the result of a strain improvement program of classical mutation and selection and/or recombinant technology (both random and targeted integration of genes). Results show that the pattern of secondary metabolites remains the same or a gradual disappearance of the formation of secondary metabolites is observed. In any case, either by applying classical or by applying recombinant techniques, no novel secondary metabolites have been found.

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