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The effect of pH on glucoamylase production, glycosylation and chemostat evolution of Aspergillus niger

Wallis, Gregg L.F.; Swift, Richard J.; Atterbury, Robert J.; Trappe, Susanne; Rinas, Ursula; Hemming, Frank W.; Wiebe, Marilyn G.; Trinci, Anthony P.J.; Peberdy, John F.


Gregg L.F. Wallis

Richard J. Swift

Robert J. Atterbury

Susanne Trappe

Ursula Rinas

Frank W. Hemming

Marilyn G. Wiebe

Anthony P.J. Trinci

John F. Peberdy


The effect of ambient pH on production and glycosylation of glucoamylase (GAM) and on the generation of a morphological mutant produced by Aspergillus niger strain B1 (a transformant containing an additional 20 copies of the homologous GAM glaA gene) was studied. We have shown that a change in the pH from 4 to 5.4 during continuous cultivation of the A. niger B1 strain instigates or accelerates the spontaneous generation of a morphological mutant (LB). This mutant strain produced approx. 50% less extracellular protein and GAM during both chemostat and batch cultivation compared to another strain with parental-type morphology (PS). The intracellular levels of GAM were also lower in the LB strain. In addition, cultivation of the original parent B1 strain in a batch-pulse bioreactor at pH 5.5 resulted in a 9-fold drop in GAM production and a 5-fold drop in extracellular protein compared to that obtained at pH 4. Glycosylation analysis of the glucoamylases purified from shake-flask cultivation showed that both principal forms of GAM secreted by the LB strain possessed enhanced galactosylation (2-fold), compared to those of the PS. Four diagnostic methods (immunostaining, mild methanolysis, mild acid hydrolysis and β-galactofuranosidase digestion) provided evidence that the majority of this galactose was of the furanoic conformation. The GAMs produced during batch-pulse cultivation at pH 5.5 similarly showed an approx. 2-fold increase in galactofuranosylation compared to pH 4. Interestingly, in both cases the increased galactofuranosylation appears primarily restricted to the O-linked glycan component. Ambient pH therefore regulates both GAM production and influences its glycosylation.


Wallis, G. L., Swift, R. J., Atterbury, R. J., Trappe, S., Rinas, U., Hemming, F. W., …Peberdy, J. F. (2001). The effect of pH on glucoamylase production, glycosylation and chemostat evolution of Aspergillus niger. BBA - General Subjects, 1527(3), doi:10.1016/S0304-4165(01)00145-3

Journal Article Type Article
Acceptance Date Apr 19, 2001
Online Publication Date Jul 25, 2001
Publication Date Aug 15, 2001
Deposit Date Aug 30, 2017
Journal Biochimica et Biophysica Acta - General Subjects
Electronic ISSN 0304-4165
Publisher Elsevier
Peer Reviewed Peer Reviewed
Volume 1527
Issue 3
Keywords pH, Glucoamylase, Galactofuranose, Aspergillus niger
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