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 language | English |
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Pages (from-to) | 163-172 |
Journal | Biomolecular Engineering |
Volume | 21 |
Issue number | 6 |
DOIs | |
Publication status | Published - 2005 |
Keywords
- flow-through cell
- bacillus-coagulans
- fungal growth
- morphology
- particle
- kinetics
- online
- hyphae
- limitation
- mycelia