Paper Title
Yeast Viability Assessment During Bioethanol Production

The viability of cell suspensions from bioethanol production was studied, using new fluorescent dye Sofia Green. The DNA binding dye Sofia Green was compared to one of the most commonly used nucleic acid binding dyes propidium iodide. The comparison of emission spectra of Sofia Green and propidium iodide before and after interaction with DNA was made. The emission intensity of Sofia Green before binding to DNA was 9 time lower than emission intensity of propidium iodide. The emission amplification of Sofia Green after the interaction with DNA was 15 times more than emission amplification of propidium iodide. The new dye has a low background and high emission amplification. Sofia Green dye was used to stain samples taken from Fermentor 3 of local factory for bioethanol production. The fermentation was carried out with corn mash and Saccharomyces cerevisiae yeast with high ethanol tolerance. It can be seen that the observed impurities from corn mash were not stained with Sofia green and were not visible on the microscopic fluorescence image. Propidium iodide had a significant background and impurities from corn mash were stained and give false positive results. A series of experiments were carried out to determine the total count, the count of dead cells and cell viability in samples taken from bioethanol production, from the pre-fermentor and from seven consecutive fermentors using fluorescence image cytometer EasyCounnter YC and Sofia Green dye. The highest viability was observed in the pre-fermentor - 84.3%. Then viability gradually decreases with the increasing number of fermenters from 81% to 58%, in the last fermenter. From first to fourth fermenter the viability decreased only with 5%. The results showed that the Sofia Green dye can be used for direct yeast cell staining in corn mash samples and give a precise cell viability results. Keywords - Bioethanol, DNA Dye, Image Cytometry, Yeast Viability