Effect of low oxygen concentrations on growth and alpha-amylase production of Aspergillus oryzae in model solid-state fermentation systems

Y.S.P. Rahardjo, S. Sie, F.J. Weber, J. Tramper, A. Rinzema

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48 Citations (Scopus)

Abstract

Oxygen transfer in the fungal mat is a major concern in solid-state fermentation (SSF). Oxygen supply into the mycelial layers is hampered by diffusion limitation. For aerobic fungi, like Aspergillus oryzae, this oxygen depletion can be a severely limiting factor for growth and metabolite production. This paper describes the effects of a low oxygen concentration on growth at the levels of individual hyphae, colonies and overcultures, and on a-amylase production in overcultures. PDA medium was used to study the effect of a low oxygen concentration on hyphal elongation rate and branching frequency of hyphae, and radial extension rate of colonies of A. oryzae. We found similar saturation constants (KO2) of 0.1% (v/v in the gas phase) for oxygen concentration described with Monod kinetics, for branching frequency of hyphae and colony extension rate. When A. oryzae was grown as an over-culture on wheat-flour model substrate at 0.25% (v/v) oxygen concentration, the reduction in growth was more pronounced than as individual hyphae and a colony on PDA medium. Experimental results also showed that the specific a-amylase production rate under the condition of 0.25% (v/v) oxygen was reduced. Because the value of KO2 is relatively low, it is reasonable to simplify the kinetics of growth of A. oryzae to zero-order kinetics in coupled diffusion/reaction models.
Original languageEnglish
Pages (from-to)163-172
JournalBiomolecular Engineering
Volume21
Issue number6
DOIs
Publication statusPublished - 2005

Keywords

  • flow-through cell
  • bacillus-coagulans
  • fungal growth
  • morphology
  • particle
  • kinetics
  • online
  • hyphae
  • limitation
  • mycelia

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