Fig. 4

Leavening ability of the strains. a CO₂ production in lean dough before freezing. b CO₂ production in lean dough after freeze-thawing at – 20 °C for 7 days. c Leavening ability was determined by the millilitre of increased volume per hour per gram (dry weight) of yeast cells. d Relative fermentation ability was determined by the ratio of leavening ability after freeze-thawing to that before stress, and the results were expressed relative to that of the parental strain ABY3 (defined as 100%). ABY3: the parental strain; ABY+YP: the strain carrying the vector Yep-PK used as a blank control to demonstrate any possible effect of the empty vector; ABY+S: the transformant carrying SNF1 overexpression. Significant differences among the three strains (ABY3, ABY+YP, and ABY+S) were confirmed at *p < 0.05