Viability of Saccharomyces Cerevisiae Cells Exposed to Low-amperage Electrolysis As Assessed by Staining Procedure and ATP Content

Assessment of yeast viability by plate counts, ATP determination and FUN-1 viability staining was performed to study sublethal injury of Saccharomyces cerevisiae cells submitted to low-amperage electrolysis. Lethal effects of electrolysis were confirmed by all methods, demonstrated by the decrease in viable counts observed during electrolysis. FUN-1 viability staining and ATP determination appeared to demonstrate higher survivors than plate counts. To study possible recovery of certain yeast cells damaged by electrolysis thus rendering them nonculturable, yeast suspensions were stored in phosphate buffer at 4 and 20 degrees C. Increase in viable counts and ATP content of treated yeast cells was observed during storage at 20 degrees C, whereas viable counts of treated and control yeast cells were shown to decrease during storage at 4 degrees C. The increase in the number of viable cells appeared to be the result of repair of damaged cells rather than regrowth of few cells remaining culturable. The lethal efficacy of electrolysis might be overestimated by plate counts. Further experiments must be done to evaluate the lethal efficacy of electrolysis on microorganisms in real conditions encountered in food products.