Analytical Sciences

Spectrophotometric Assay of Yeast Vitality Using 2,3,5,6-Tetramethyl-1,4-benzoquinone and Tetrazolium Salts

Tadayuki TSUKATANI,*  Takahiro OBA,* Hiroyuki UKEDA,** and Kiyoshi MATSUMOTO***

*Biotechnology and Food Research Institute, Fukuoka Industrial Technology Center, Kurume 839-0861, Japan
**Department of Bioresources Science, Faculty of Agriculture, Kochi University, Nankoku 783-8502, Japan
***Division of Food Biotechnology, Department of Bioscience and Biotechnology, Faculty of Agriculture, Graduate School Kyushu University, Fukuoka 812-8581, Japan

A method for the spectrophotometric assay of yeast vitality was developed using 2,3,5,6-tetramethyl-1,4-benzoquinone and tetrazolium salts. The metabolic efficiency of 2,3,5,6-tetramethyl-1,4-benzoquinone by yeast cells was used as an index of yeast vitality. 2,3,5,6-Tetramethyl-1,4-benzoquinone was reduced to 2,3,5,6-tetramethyl-1,4-hydroquinone by yeast cells. Then, the superoxide anion radicals generated from O₂ by reduction with 2,3,5,6-tetramethyl-1,4-hydroquinone under alkaline conditions reduced tetrazolium salts to formazan, which exhibited absorbance maxima at 440 nm. A linear relationship between the absorbance and viable cell density was obtained in the range of 1.0 x 10⁵ - 2.0 x 10⁷ cells/ml for a sample solution. During the cultivation of yeast cells, the absorbance showed almost an anti-parallel change with that of glucose in yeast growth and fermentation, suggesting that the absorbance change reflected the vitality of yeast cells.

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