Yeast cells viability in industrial fermentation media determined by high-resolution growth curves

The inhibitory compounds present in lignocellulosic hydrolysate heavily affect viability of yeast cells during ethanol fermentation. Yeast viability can be correlated with the metabolic capacity of the cells and therefore with potential ethanol productivity. In addition, if advanced –omics studies have to be performed on yeast cells populations exposed to fermentation inhibitors, it is important to know what percentage of the cells population is viable. Cell viability is usually determined through count of colony forming units on plates or by staining cells with metabolically activated dyes. However, these methods are labour intensive and results are often not representative of the real cell population state, due to the inherent variability of the methods.The Bioscreen C MBR instrument allows to perform up to 200 growth curves in miniaturized scale. Besides allowing the estimation of the maximum specific growth rate of cells in a large array of conditions, the instrument could be used for the description of high-resolution growth curves and the subsequent estimation of the percentage of viable cells in the inoculum.Here we show the optimization of shaking parameters, inoculum size and media formulation for optimal growth curve description. In addition we present the strategy for validating the use of the instrument for viability estimation