Morphological and enzymatic responses of a recombinant aspergillus niger to oxidative stressors in chemostat cultures

M. Kreiner, L.M. Harvey, B. McNeil

Research output: Contribution to journalArticle

30 Citations (Scopus)

Abstract

Continuous chemostat cultures of a recombinant strain of Aspergillus niger (B1-D), engineered to produce the marker protein hen egg white lysozyme, were investigated with regard to their susceptibility to oxidative stress. The culture response to oxidative stress, produced either by addition of exogenous hydrogen peroxide (H2O2) or by high dissolved oxygen tension (DOT), was characterised in terms of the activities of two key defensive enzymes: catalase (CAT) and superoxide dismutase (SOD). Since the morphology is so critical in submerged fungal bioprocesses, the key morphological indices were analysed using a semi-automated image analysis system. Both oxidant stressors, H2O2 and elevated DOT, increased both enzyme activities, however, the extent was different: exogenous H2O2 led mainly to increased CAT activity, whereas gassing with O2 enriched air, which resulted in a DOT of 165% of air saturation, increased both enzyme activities more than 2-fold compared with the control steady state culture. Addition of exogenous H2O2 resulted in shorter hyphae compared with control steady state cultures. These findings indicate that it is unsound to use exogenous H2O2 to simulate oxidative stress induced by elevated dissolved oxygen levels since the response to each might be quite different, both in terms of enzymatic (defensive) responses and in terms of culture morphology.
LanguageEnglish
Pages251-260
Number of pages10
JournalJournal of Biotechnology
Volume100
Issue number3
DOIs
Publication statusPublished - 2003

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Aspergillus niger
Oxygen
Oxidative Stress
Catalase
Enzymes
Air
Hyphae
Oxidants
Hydrogen Peroxide
Superoxide Dismutase
Proteins

Keywords

  • aspergillus niger
  • oxidative stress
  • oxygen enrichment
  • hydrogen peroxide
  • superoxide dismutase
  • catalase

Cite this

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title = "Morphological and enzymatic responses of a recombinant aspergillus niger to oxidative stressors in chemostat cultures",
abstract = "Continuous chemostat cultures of a recombinant strain of Aspergillus niger (B1-D), engineered to produce the marker protein hen egg white lysozyme, were investigated with regard to their susceptibility to oxidative stress. The culture response to oxidative stress, produced either by addition of exogenous hydrogen peroxide (H2O2) or by high dissolved oxygen tension (DOT), was characterised in terms of the activities of two key defensive enzymes: catalase (CAT) and superoxide dismutase (SOD). Since the morphology is so critical in submerged fungal bioprocesses, the key morphological indices were analysed using a semi-automated image analysis system. Both oxidant stressors, H2O2 and elevated DOT, increased both enzyme activities, however, the extent was different: exogenous H2O2 led mainly to increased CAT activity, whereas gassing with O2 enriched air, which resulted in a DOT of 165{\%} of air saturation, increased both enzyme activities more than 2-fold compared with the control steady state culture. Addition of exogenous H2O2 resulted in shorter hyphae compared with control steady state cultures. These findings indicate that it is unsound to use exogenous H2O2 to simulate oxidative stress induced by elevated dissolved oxygen levels since the response to each might be quite different, both in terms of enzymatic (defensive) responses and in terms of culture morphology.",
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Morphological and enzymatic responses of a recombinant aspergillus niger to oxidative stressors in chemostat cultures. / Kreiner, M.; Harvey, L.M.; McNeil, B.

In: Journal of Biotechnology, Vol. 100, No. 3, 2003, p. 251-260.

Research output: Contribution to journalArticle

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AU - Harvey, L.M.

AU - McNeil, B.

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N2 - Continuous chemostat cultures of a recombinant strain of Aspergillus niger (B1-D), engineered to produce the marker protein hen egg white lysozyme, were investigated with regard to their susceptibility to oxidative stress. The culture response to oxidative stress, produced either by addition of exogenous hydrogen peroxide (H2O2) or by high dissolved oxygen tension (DOT), was characterised in terms of the activities of two key defensive enzymes: catalase (CAT) and superoxide dismutase (SOD). Since the morphology is so critical in submerged fungal bioprocesses, the key morphological indices were analysed using a semi-automated image analysis system. Both oxidant stressors, H2O2 and elevated DOT, increased both enzyme activities, however, the extent was different: exogenous H2O2 led mainly to increased CAT activity, whereas gassing with O2 enriched air, which resulted in a DOT of 165% of air saturation, increased both enzyme activities more than 2-fold compared with the control steady state culture. Addition of exogenous H2O2 resulted in shorter hyphae compared with control steady state cultures. These findings indicate that it is unsound to use exogenous H2O2 to simulate oxidative stress induced by elevated dissolved oxygen levels since the response to each might be quite different, both in terms of enzymatic (defensive) responses and in terms of culture morphology.

AB - Continuous chemostat cultures of a recombinant strain of Aspergillus niger (B1-D), engineered to produce the marker protein hen egg white lysozyme, were investigated with regard to their susceptibility to oxidative stress. The culture response to oxidative stress, produced either by addition of exogenous hydrogen peroxide (H2O2) or by high dissolved oxygen tension (DOT), was characterised in terms of the activities of two key defensive enzymes: catalase (CAT) and superoxide dismutase (SOD). Since the morphology is so critical in submerged fungal bioprocesses, the key morphological indices were analysed using a semi-automated image analysis system. Both oxidant stressors, H2O2 and elevated DOT, increased both enzyme activities, however, the extent was different: exogenous H2O2 led mainly to increased CAT activity, whereas gassing with O2 enriched air, which resulted in a DOT of 165% of air saturation, increased both enzyme activities more than 2-fold compared with the control steady state culture. Addition of exogenous H2O2 resulted in shorter hyphae compared with control steady state cultures. These findings indicate that it is unsound to use exogenous H2O2 to simulate oxidative stress induced by elevated dissolved oxygen levels since the response to each might be quite different, both in terms of enzymatic (defensive) responses and in terms of culture morphology.

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