Culture-Based Strategies for Reduction of Protease Activity in Filtrates from Aspergillus niger NRRL-3 |
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Authors: | Aftab Ahamed Ajay Singh Owen P Ward |
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Institution: | (1) Department of Biology, University of Waterloo, N2L 3G1 Waterloo, Ontario, Canada |
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Abstract: | Summary While Aspergillus strains are also being considered as potential hosts for production of extracellular heterologous proteins, the proteases
produced by the host are highly problematic in that they typically modify and degrade the recombinant proteins. Culture-based
approaches for minimization of protease activity in culture supernatants of Aspergillus niger NRRL-3 included reduction or elimination of peptide nitrogen in the medium, preferential use of a defined salts medium rather
than a non-peptide nitrogen medium containing yeast-nitrogen base, supplementation of the medium with carboxymethylcellulose
and cultivation at pH 6.5 rather than 7.5. In general, increased proteolytic activity was observed after maximum biomass was
observed and biomass was declining suggesting the majority of protease activity was released by cell lysis. Carboxymethylcellulose
shifted mycelial morphology from pelleted to filamentous. Mycelium lysis in the centre of pellets, with resultant release
of intracellular proteases, would explain why filamentous cultures exhibited much lower proteolytic activity than pelleted
cultures. |
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Keywords: | Aspergillus niger culture strategies filamentous growth pelleted growth protease |
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