The present invention provides yeast belonging to the genus Saccharomyces which generates, in dough containing 5% sugar, carbon dioxide gas in an amount of not less than 2.0 ml per g of the dough and not less than 1.20 ml per ml of volume expansion of the dough at 38.degree. C. in 60 minutes; a method of screening for the yeast; bread dough containing the yeast; a process for making bread using the yeast; and bread having an anti-mold effect which is obtained by the process.