Rapid counting method of living cells by fluorescent enzyme substrates.

The 5(and 6)-carboxyfluorescein diacetate (C-FDA) is used for a rapid and continuous counting of living cells. Nonfluorescent C-FDA is converted into fluorescent 5(and 6)-carboxyfluorescein (C-F) by the reaction with esterase, which is an enzyme of living cells. The conversion makes it possible to count the number of living cells by detecting fluorescence. Experimental results show that the living cells of beer's yeast, E. coli, and Lactobacillus bulgaricus can be detected by fluorescence. The flow cell system was used to experiment a continuous detection of living cells, so that the number of living cells of beer's yeast can be detected continuously. The proposed method can be applied to the on-line counting in the food plants.