1887

Abstract

Accounting for a cooperativity effect in substrate uptake by a microbial culture leads to a Hill type of equation for the specific rate of substrate uptake (), that is,

where is substrate concentration, is the Hill number and is a constant. For substrates such as N or P, which are conserved in the biomass, the substrate content of the biomass () will vary according to the relation

where is the minimum substrate content of the biomass, occurring when → 0, and is the maximum substrate content of the biomass, occurring when the biomass is saturated with substrate. The specific growth rate is given by

where is a constant given by / . If the substrate is conserved, = 1/ and = 1/ where and are the maximum and minimum yields from the substrate, respectively.

Experimental tests of these relations applied to N (urea)-limited growth of in chemostat cultures showed satisfactory agreement between the results and the theory. For N uptake the growth constants were = 5·5, = 0·47, = ( ) = 82 g N l, = = 94 g N l. The apparent departure of from unity in N-limited growth can be accounted for by starch storage in the biomass.

For P (phosphate)-limited growth, = 1·3, = 0·15 and was about 28 g P l. A discrepancy was found between the value for P uptake obtained from the data and that from the data. This discrepancy may be attributed to phosphate storage in the biomass, which is not allowed for in the model.

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1978-10-01
2022-01-25
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