Chemostat

The chemostat culture is a common method of culturing microorganisms. In contrast to batch culture (static culture) it is a form of continuous culture of bacteria or phytoplankton.

A chemostat culture vessel is in the continuously and at a constant rate ( flow rate) of the nutrient medium is supplied. The same rate as fresh nutrient medium is supplied, spent medium including organisms suspended therein is removed via an overflow. This simulates the mortality rate of natural populations. If the flow rate in the chemostat less than the maximum growth rate of the cultured organisms, so there is set a dynamic equilibrium ( steady-state ), which corresponds to the gross growth rate of loss rate. The number of organisms per unit volume remains constant, and is, fluctuations should occur but once, self-regulating. Decreases the population density, fewer nutrients are consumed, that is, the concentration of nutrients increases. This in turn implies an increase in the number of individuals, which in turn creates a reduction in the amount of nutrients per volume by itself, etc.

By means of the chemostat, parameters of population dynamics are investigated model.

Determine the optimal dilution rate

In order to determine the optimal dilution rate, the parameters must be determined such that the rate of production is maximized. The production rate is the product of the inverse residence or dilution rate ( Dilutionsrate ) D [h- 1] (the nominal frequency of replacement of the reactor volume, the quotient of Volumenzu-/abfluss and liquid reactor volume ) and the biomass concentration x [ typically gBiomasse L -1]. Since the concentration of biomass in the reactor should remain constant, valid for the growth rate: μ = D.

It applies to the maximum production rate:

The production rate reaches its theoretical maximum near the critical Dilutionsrate Dcrit. after which the growth rate is less than the dilution rate, and therefore the decreases in the biomass reactor. The maximum productive dilution rate of the chemostat is for exponential growth is given by:

With being the substrate concentration in the inlet and Ks the Monod constant. Dopt here lies near the critical dilution rate Dcrit .. Because from this, the biomass is flushed out faster than it is formed, a chemostat is typically not operated on this potentially unstable operating point.