Metabolism of benzoquinone by yeast cells and oxidative characteristics of corresponding hydroquinone: application to highly sensitive measurement of yeast cell density by using benzoquinone and a chemiluminescent probe

The metabolic efficiency of seven derivatives of 1,4-benzoquinone (BQ) by yeast cells and the oxidative characteristics of the corresponding hydroquinones (HQs) were studied by electrochemical, spectrophotometric and chemiluminescent methods. The spectrophotometric method was based on the reduction of a tetrazolium salt to formazan dye during the autoxidation of HQs generated by yeast cells under alkaline conditions. The amounts of HQs detected directly by the electrochemical method did not agree with those calculated from the formazan dye obtained by the spectrophotometric method. A tetrazolium salt was reduced to a formazan dye by both the superoxide anion radical (O2-*) generated during the autoxidation of 2,3,5,6-tetramethyl-1,4-HQ and by HQ itself. Little formazan dye was formed, and hydrogen peroxide (H2O2) was then finally produced during the autoxidation of 1,4-HQ or 2-methyl-1,4-HQ. Formazan dye and H2O2 were generated at a certain ratio during the autoxidation of derivatives of dimethyl-1,4-HQ or 2,3,5-trimethyl-1,4-HQ. The analytical method based on chemiluminescence with lucigenin and 2,3,5,6-tetramethyl-1,4-BQ was applied to highly sensitive measurement of the yeast cell density. A linear relationship between the chemiluminescence intensity and viable cell density was obtained in the range of 1.2 x 10(3) - 4.8 x 10(4) cells/ml. The detection limit was 4.8 x 10(2) cells/ml.