Ref ID : 964
Oliver J. Hao, Michael G. Richard, David Jenkins, and Harvey W. Blanch; The half-saturation coefficient for dissolved oxygen: A dynamic method for its determination and its effect on dual species competition. Biotechnology and Bioengineering XXV:403-416, 1983
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A simple approach was developed to determine the half-saturation coefficient for dissolved oxygen (KDO) for three bacteria by maintaining a constant oxygen concentration in continuous culture, and employing a dynamic method to obtain the specific growth rate (u) for each species. Measurement of (u) at selected dissolved oxygen concentrations (DO) resulted in a typical Monod curve for a plot of (u) vs. (DO). Values for KDO and u(max) were obtained from the Lineweaver-Burk reciprocal plot. The bacteria studied included representative strains of three microorganisms isolated in pure culture from poorly settling activated sludge: two filamentous microorganisms, Sphaerotilus natans and a second Sphaerotilus sp., and an unidentified floc-forming microorganism. The KDO values obtained for Sphaerotilus sp., S. natans, and the floc former were 0.014, 0.033, and 0.073 mg/L, respectively. Dual-species competition experiments were conducted in continuous culture under low and high DO conditions. Successful growth competition by these microorganisms under DO-limiting conditions was consistent with experimentally determined KDO values. The finding of lower KDO values for the two Sphaerotilus species, compared to the floc former, confirmed the hypothesis that these filamentous microorganisms can outgrow floc-forming microorganisms in activated sludge when DO in the aeration basin is low.