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

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Author: Swift, R.J. · Karandikar, A. · Griffen, A.M. · Punt, P.J. · Hondel, C.A.M.J.J. van den · Robson, G.D. · Trinci, A.P.J. · Wiebe, M.G.
Type:article
Date:2000
Institution: Centraal Instituut voor Voedingsonderzoek TNO
Source:Fungal Genetics and Biology, 2, 31, 125-133
Identifier: 72250
doi: doi:10.1006/fgbi.2000.1241
Keywords: Biology · Aspergillus niger · Chemostat culture · Genetic instability · Glucoamylase · Nitrogen source · Recombinant protein · Alanine · Casamino acid · DNA · Fungal DNA · Fungal enzyme · Glucan 1,4 alpha glucosidase · Glucose · Methionine · Nitro derivative · Peptone · Aspergillus niger · Chemostat · Controlled study · Culture medium · DNA methylation · Enzyme metabolism · Enzyme synthesis · Fermentation · Fungal genetics · Fungus culture · Gene loss · Morphology · Nonhuman · PH · Priority journal · Strain difference · Aspergillus niger · Culture Media · Glucan 1,4-alpha-Glucosidase · Glucose · Hydrogen-Ion Concentration · Mutation · Nitrogen · Organic Chemicals · Recombinant Proteins · Aspergillus niger

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.