Physiological responses of chemostat cultures of aspergillus niger (B1-D) to simulated and actual oxidative stress

Z. Bai, L.M. Harvey, B. McNeil

Research output: Contribution to journalArticle

31 Citations (Scopus)

Abstract

The physiological responses of chemostat cultures of the filamentous fungus, Aspergillus niger (B1-D) to simulated and actual oxidative stress, imposed respectively by addition of exogenous menadione (MD; a superoxide radical generating reagent) and gassing the culture with oxygen enriched air (25%, 50%, 75%, and 100% [v/v]), were examined. Changes in the levels of intracellular superoxide anions and defensive enzyme activities, such as catalase (CAT), superoxide dismutase (SOD), and glutathione peroxidase (GPx), were monitored, together with glutathione and respiratory activity in both the dynamic phase and when a new steady state was established. Culture response to MD addition was distinct from that upon exposure to enriched oxygen conditions, in that MD caused elevated levels of intracellular protein, whereas oxygen enrichment caused reduced protein content, especially at low dilution rates. An unexpectedly low level of superoxide radical was found in oxygen-enriched steady-state cultures (50%) at a range of dilution rates, which was not caused by elevated SOD activity. Under these conditions, it was noted that the ratio of rotenone-insensitive/total respiration increased, suggesting increased activity of the alternative respiratory pathway. This may have had the effect of reducing the endogenous generation of superoxide radicals under oxygen rich conditions, but also may have reduced the ATP yield due to the non-proton-pumping nature of the alternative respiratory pathway. Thus, the negative culture effects noted in many studies at high oxygen levels may not simply be due to elevated endogenous superoxide generation, but could be in part due to the consequences of metabolic changes in the culture that seek to minimize superoxide generation. The dynamic culture response was characterized by rapid elevation of intracellular superoxide anions and associated protective enzymes, especially SOD, and was clearly distinct from the adaptive response just described.
Original languageEnglish
Pages (from-to)691-701
Number of pages10
JournalBiotechnology and Bioengineering
Volume82
Issue number2
DOIs
Publication statusPublished - 2003

Fingerprint

Chemostats
Oxidative stress
Aspergillus niger
Aspergillus
Superoxides
Oxidative Stress
Oxygen
Superoxide Dismutase
Dilution
Negative ions
Proteins
Adenosinetriphosphate
Vitamin K 3
Rotenone
Enzyme activity
Fungi
Enzymes
Glutathione Peroxidase
Catalase
Glutathione

Keywords

  • aspergillus niger
  • oxidative stress
  • alternative respiratory pathway
  • biomedical sciences
  • pharmacology

Cite this

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title = "Physiological responses of chemostat cultures of aspergillus niger (B1-D) to simulated and actual oxidative stress",
abstract = "The physiological responses of chemostat cultures of the filamentous fungus, Aspergillus niger (B1-D) to simulated and actual oxidative stress, imposed respectively by addition of exogenous menadione (MD; a superoxide radical generating reagent) and gassing the culture with oxygen enriched air (25{\%}, 50{\%}, 75{\%}, and 100{\%} [v/v]), were examined. Changes in the levels of intracellular superoxide anions and defensive enzyme activities, such as catalase (CAT), superoxide dismutase (SOD), and glutathione peroxidase (GPx), were monitored, together with glutathione and respiratory activity in both the dynamic phase and when a new steady state was established. Culture response to MD addition was distinct from that upon exposure to enriched oxygen conditions, in that MD caused elevated levels of intracellular protein, whereas oxygen enrichment caused reduced protein content, especially at low dilution rates. An unexpectedly low level of superoxide radical was found in oxygen-enriched steady-state cultures (50{\%}) at a range of dilution rates, which was not caused by elevated SOD activity. Under these conditions, it was noted that the ratio of rotenone-insensitive/total respiration increased, suggesting increased activity of the alternative respiratory pathway. This may have had the effect of reducing the endogenous generation of superoxide radicals under oxygen rich conditions, but also may have reduced the ATP yield due to the non-proton-pumping nature of the alternative respiratory pathway. Thus, the negative culture effects noted in many studies at high oxygen levels may not simply be due to elevated endogenous superoxide generation, but could be in part due to the consequences of metabolic changes in the culture that seek to minimize superoxide generation. The dynamic culture response was characterized by rapid elevation of intracellular superoxide anions and associated protective enzymes, especially SOD, and was clearly distinct from the adaptive response just described.",
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Physiological responses of chemostat cultures of aspergillus niger (B1-D) to simulated and actual oxidative stress. / Bai, Z.; Harvey, L.M.; McNeil, B.

In: Biotechnology and Bioengineering, Vol. 82, No. 2, 2003, p. 691-701.

Research output: Contribution to journalArticle

TY - JOUR

T1 - Physiological responses of chemostat cultures of aspergillus niger (B1-D) to simulated and actual oxidative stress

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AU - Harvey, L.M.

AU - McNeil, B.

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KW - alternative respiratory pathway

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DO - 10.1002/bit.10614

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