A rapid electrochemical method for assimilation test of microorganisms

Summary A microbial electrode consisting of the immobilized microorganisms to be tested and an oxygen electrode was used to study the assimilation characteristics of microorganisms. When a sample solution containing a substrate was injected into the microbial sensor system, the current of the sensor markedly decreased with time if the microorganisms assimilated the substrate. On the other hand, no current decrease was observed if the microorganisms could not assimilate the substrate. Assimilation characteristics of various microorganisms such as molds, yeasts, bacteria, actinomycetes and activated sludges were tested with various substrates. The time required for a test was 30 min per substrate by the pulse method (sample injection period, 5 min). Good correlations were obtained between this electrochemical method and the conventional growth test. The fundamental differences between the two methods and the application of the electrochemical method are discussed.