The effects of bioprocess parameters on extracellular proteases in a recombinant Aspergillus niger B1-D

Qiang Li, Brian McNeil, Linda M. Harvey

Research output: Contribution to journalArticle

7 Citations (Scopus)

Abstract

Although host proteases are often considered to have a negative impact upon heterologous protein production by filamentous fungi, relatively little is known about the pattern of their appearance in recombinant fungal bioprocesses. In the present study, we investigated extracellular proteases from a filamentous fungus, Aspergillus niger B1-D, genetically modified to secrete hen egg white lysozyme (HEWL). Our findings indicate that extracellular protease activity is only detected after the carbon source is completely utilised in batch cultures. The proteases are predominantly acid proteases and have optimal temperature for activity at around 45°C. Their activity could be partially inhibited by protease inhibitors, indicating the existence of at least four kinds of proteases in these culture fluids, aspartic-, serine-, cysteine-, and metallo-proteases. Oxygen enrichment does not have any noticeable effects on extracellular protease activity except that the onset of protease activity appears earlier in oxygen enrichment runs. Oxygen enrichment stimulates HEWL production substantially, and we propose that it is related to fungal morphology. Thermal stress imposed by raising process temperature (from 25 to 30 and 35°C) in early exponential phase, led to appearance of protease activity in the medium following the heat shock. Continued cultivation at high temperatures significantly reduced HEWL production, which was associated with increased activity of the extracellular proteases in these cultures.
LanguageEnglish
Pages333-341
Number of pages8
JournalApplied Microbiology and Biotechnology
Volume78
Issue number2
DOIs
Publication statusPublished - 2008

Fingerprint

Aspergillus niger
Peptide Hydrolases
Egg White
Oxygen
Temperature
Fungi
Hot Temperature
Batch Cell Culture Techniques
Cysteine Proteases
Protease Inhibitors
Serine
Shock
Carbon
Acids

Keywords

  • heterologous protein
  • extracellular proteases' hen egg white
  • lysozyme
  • aspergillus niger
  • fermentation
  • pharmacology

Cite this

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abstract = "Although host proteases are often considered to have a negative impact upon heterologous protein production by filamentous fungi, relatively little is known about the pattern of their appearance in recombinant fungal bioprocesses. In the present study, we investigated extracellular proteases from a filamentous fungus, Aspergillus niger B1-D, genetically modified to secrete hen egg white lysozyme (HEWL). Our findings indicate that extracellular protease activity is only detected after the carbon source is completely utilised in batch cultures. The proteases are predominantly acid proteases and have optimal temperature for activity at around 45°C. Their activity could be partially inhibited by protease inhibitors, indicating the existence of at least four kinds of proteases in these culture fluids, aspartic-, serine-, cysteine-, and metallo-proteases. Oxygen enrichment does not have any noticeable effects on extracellular protease activity except that the onset of protease activity appears earlier in oxygen enrichment runs. Oxygen enrichment stimulates HEWL production substantially, and we propose that it is related to fungal morphology. Thermal stress imposed by raising process temperature (from 25 to 30 and 35°C) in early exponential phase, led to appearance of protease activity in the medium following the heat shock. Continued cultivation at high temperatures significantly reduced HEWL production, which was associated with increased activity of the extracellular proteases in these cultures.",
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The effects of bioprocess parameters on extracellular proteases in a recombinant Aspergillus niger B1-D. / Li, Qiang; McNeil, Brian; Harvey, Linda M.

In: Applied Microbiology and Biotechnology, Vol. 78, No. 2, 2008, p. 333-341.

Research output: Contribution to journalArticle

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AU - McNeil, Brian

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