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The yeast strain AK 46 was isolated from dough containing fermented cherry fruits and identified as Saccharomyces cerevisiae. The nucleotide sequence of the rDNA spacer region from this strain coincided with those from the yeasts used for the production of whisky, wine, and bread. In a comparison with six baking strains, strain AK 46 possessed less leavening ability in dough with and without addition of 5% sucrose (based on the weight of flour) but a high ability in sweet dough containing 30% sucrose. The activities of the two enzymes α-glucosidase and invertase, which are related to dough fermentation, were lower than those in the other strains. A baking test showed that strain AK 46 was applicable for breadmaking using the straight dough and sponge dough methods. Strain AK 46 carried only SUC2, which is one of multiple genes encoding invertase, in contrast to the other baking strains, and its sequences diverged from those of the corresponding gene from a representative laboratory strain. Southern hybridization of genomic DNA, using the SUC2 gene as the probe, readily discriminated strain AK 46 and other strains. These observations indicate that strain AK 46 is a wild strain possessing breadmaking properties.

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The wild yeast Saccharomyces cerevisiae AK46 was isolated from cherry fruits and commercialized as baker's yeast. We isolated a 2-deoxyglucose (2-DOG)-resistant mutant of AK46 (MCD4) and evaluated its leavening ability in bread dough. Our findings show that the maltose utilization of MCD4 was significantly enhanced in the presence of glucose and α-glucosidase activity was increased by approx. 1.6-fold compared to that of AK46, indicating release from catabolite repression. In addition, baking performance results using the sponge dough and no-time dough methods showed that the CO 2 production rate of MCD4 was increased by approx. 1.6-fold (sponge and dough method) and the specific volume of bread was increased by 6.3% and 7.8%, respectively. These results demonstrate that the 2-DOG resistance exhibited by MCD4 significantly improved the leavening ability in bread dough.