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

Biochim Biophys Acta. 2001 Aug 15;1527(3):112-22. doi: 10.1016/s0304-4165(01)00145-3.


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 beta-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.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Aspergillus niger / enzymology
  • Aspergillus niger / genetics
  • Aspergillus niger / metabolism*
  • Culture Media
  • Glucan 1,4-alpha-Glucosidase / biosynthesis
  • Glucan 1,4-alpha-Glucosidase / genetics
  • Glucan 1,4-alpha-Glucosidase / metabolism*
  • Glycoproteins / biosynthesis
  • Glycosylation
  • Hydrogen-Ion Concentration
  • Isoenzymes / metabolism
  • Monosaccharides / analysis
  • Monosaccharides / metabolism
  • Mutation
  • Polysaccharides
  • Recombination, Genetic


  • Culture Media
  • Glycoproteins
  • Isoenzymes
  • Monosaccharides
  • Polysaccharides
  • maltodextrin
  • Glucan 1,4-alpha-Glucosidase