The effect of organic nitrogen sources on recombinant glucoamylase production by Aspergillus niger in chemostat culture
article
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.
Topics
Aspergillus nigerChemostat cultureGenetic instabilityGlucoamylaseNitrogen sourceRecombinant proteinAlanineCasamino acidDNAFungal DNAFungal enzymeGlucan 1,4 alpha glucosidaseGlucoseMethionineNitro derivativePeptoneAspergillus nigerChemostatControlled studyCulture mediumDNA methylationEnzyme metabolismEnzyme synthesisFermentationFungal geneticsFungus cultureGene lossMorphologyNonhumanPHPriority journalStrain differenceAspergillus nigerCulture MediaGlucan 1,4-alpha-GlucosidaseGlucoseHydrogen-Ion ConcentrationMutationNitrogenOrganic ChemicalsRecombinant ProteinsAspergillus niger
TNO Identifier
72250
ISSN
10871845
Source
Fungal Genetics and Biology, 31(2), pp. 125-133.
Pages
125-133
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