A Computer-Controlled Turbidostat for the Culture of Planktonic Algae

Abstract

We designed, built, and tested a microprocessor-controlled turbidostat that maintains phytopSankton cells at nearly constant biomass concentrations without nutrient limitation of growth rates. There are fundamental limits placed on the achievable degree of constancy by physiological changes in the organisms being cultured. The sensor responds nearly linearly over a wide range of cell densities, extending well into high pigment concentrations (approx. 20 mg Chl a/m3). The microprocessor-based controller eliminates the need for time-consuming and delicate set-up and modification of operational variables and provides for simple implementation of virtually any logical feedback algorithm to control cell concentration. Although the result was not unexpected, we have shown that growth rates measured in the turbidostat are equivalent to corresponding measurements in a batch culture growing under identical conditions, until such time as the populations develop differing physiological and physical properties due to their different environments.