Brewing yeast viability measured using a novel fluorescent dye and image cytometer

Abstract

This study presents an automated, image-based cytometry method for determination of total counts and viability of yeast cells by using a newly synthesized DNA fluorescent dye PO-TEDM-1 and a new Easycounter YC instrument. The synthesized polycationic asymmetric monomethine cyanine dye PO-TEDM-1 penetrates only into dead cells. The new fluorescent dye has high nucleic acid sensitivity and rapid interaction kinetics. The optimal concentration of the fluorescent dye for staining dead cells was 1 µg mL−1. The Easycounter YC system was used to determine the total cell count and viability of Saccharomyces carlsbergensis. The actual viability measured using the proposed method significantly correlated with the theoretical viability (R2 of 0.9988). The optimal linear interval was from 1 × 105 to 1 × 107 cells mL−1. The coefficient of variation with Easycounter YC in the optimal range was 2.5–4%, whereas that of the manual hemocytometry method, in the same range was higher, 15–23%. We tested the procedure in a study of the total cell count and viability of yeast cells from the propagators in beer production as a function of the dilution. The proposed method can be used in assays involving simple cell counting and quality assurance in sample bioprocessing.

Keywords

• yeast viability
• fluorescent dye
• image cytometry
• brewing