Selection of a superior segregant from the inhibitor tolerant baker’s yeast JT21653. Fermentation was performed in semi-anaerobic conditions using treated slurry of spruce material at 77% concentration and supplemented with 70 g/L glucose. CO2 production was estimated from the weight loss. Fseg25 (blue) showed the best performance, with in particular a very short lag phase compared to the other segregants. The diploid parent JT21653 (green) and the industrial bioethanol production strain Ethanol Red (red) as well as all other segregants, except for four, were not able to ferment appreciably at this concentration of spruce hydrolysate within 120 h.