Patent ID: 7906295

Claim:
A method for measuring vitality of intact yeast cells for fermentation applications, comprising: (a) providing a sample containing yeast cells; (b) contacting said sample containing yeast cells with 1) a molecule or dye that is detectably altered by enzymatic activity of viable yeast cells, wherein the dye comprises fluorescein diacetate or OREGON GREEN™ (2′,7′ difluorofluorescein), and 2) a compound that increases the rate of uptake of the molecule or dye into the yeast cells or speeds up the rate of conversion of the molecule or dye into a detectably fluorescent form inside said yeast cells; (c) measuring a total amount of fluorescence of enzymatically altered molecule or dye in said sample of step (b), wherein the measuring is performed by a fluorometer; and (d) correlating the total amount of fluorescence of the enzymatically altered dye measured in step (c) with a viable cell count correlation measurement that correlates values of fluorescence of the enzymatically altered molecule or dye with total viable yeast cells/ml, thereby determining the number of total viable yeast cells in the sample, and thereby measuring vitality of yeast cells in the sample.