Effect of low oxygen concentrations on growth and alpha-amylase production of Aspergillus oryzae in model solid-state fermentation systems.
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 alpha-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 (K(O2)) 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 alpha-amylase production rate under the condition of 0.25% (v/v) oxygen was reduced. Because the value of K(O2) is relatively low, it is reasonable to simplify the kinetics of growth of A. oryzae to zero-order kinetics in coupled diffusion/reaction models.
Rahardjo
Yovita S P
YS
Wageningen Centre for Food Sciences, P.O. Box 557, 6700 AN Wageningen, The Netherlands. yovita.rahardjo@wur.nl
Sie
Susana
S
Weber
Frans J
FJ
Tramper
Johannes
J
Rinzema
Arjen
A
D001236:Aspergillus oryzae / Q000166:cytology / Q000201:enzymology* / Q000254:growth & development*; D019149:Bioreactors / Q000382:microbiology*; D018929:Cell Culture Techniques / Q000379:methods*; D049109:Cell Proliferation; D003198:Computer Simulation; D008954:Models, Biological; D010100:Oxygen / Q000378:metabolism*; D010101:Oxygen Consumption / Q000502:physiology; D000516:alpha-Amylases / Q000096:biosynthesis*
D000516:alpha-Amylases; D010100:Oxygen