The effect of organic nitrogen sources on recombinant glucoamylase production by Aspergillus niger in chemostat culture

Richard J. Swift, Atul Karandikar, Alison M. Griffen, Peter J. Punt, Cees A M J J Van Den Hondel, Geoffrey D. Robson, Anthony P J Trinci, Marilyn G. Wiebe

    Research output: Contribution to journalArticlepeer-review

    Abstract

    Aspergillus niger B1, a recombinant strain carrying 20 extra copies of the native glucoamylase gene, was grown in glucose-limited chemostat cultures supplemented with various organic nitrogen sources (dilution rate 0.12 ± 0.01 h-1, pH 5.4). In cultures supplemented with L-alanine, L-methionine, casamino acids, or peptone, specific glucoamylase (GAM) production rapidly decreased to less than 20% of the initial level. Reducing the pH of the culture to 4.0 resulted in stable GAM production for up to 400 h. Morphological mutants (a light brown and a dark brown mutant) appeared in each fermentation and generally displaced B1. Light brown mutants had higher selection coefficients relative to B1 than dark brown mutants and became the dominant strain in all fermentations except those maintained at pH 4.0. Several mutants isolated from these cultures had reduced ability to produce GAM in batch culture, although few had lost copies of the glaA gene. Some mutants had methylated DNA. © 2000 Academic Press.
    Original languageEnglish
    Pages (from-to)125-133
    Number of pages8
    JournalFungal Genetics and Biology
    Volume31
    Issue number2
    DOIs
    Publication statusPublished - 2000

    Keywords

    • Aspergillus niger
    • Chemostat culture
    • Genetic instability
    • Glucoamylase
    • Nitrogen source
    • Recombinant protein

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