Sizing and counting of Saccharomyces cerevisiae floc populations by image analysis, using an automatically calculated threshold

Abstract

A standardized image analysis method has been developed permitting determination of the number of yeast flocs and their size distribution. The method includes image grabbing, image enhancement, automatic determination of the appropriate threshold, curve fitting of the area histogram, determination of the mean single floc area and its standard deviation, and floc counting. The extension of the method to other applications is immediate and straightforward. Two Saccharomyces cerevisiae floc populations (with ages of 48 and 72 h) were analyzed. The results showed a variation around the mean of 9%-12% for the single floc mean area, 6%-7% for the number of single flocs, and 5%-6% for the total number of flocs. Aggregates of two flocs (doublets) and three flocs (triplets) were enumerated. The correctness of the method was checked by analyzing the parameters of interest as a function of the threshold. The constant correlation between the parameters and the threshold showed the validity and consistency of the method.