We obtained ten strains that were homozygous for wild-type
FAS2 from the parent strain -K-1801- by UV irradiation and cerulenin sensitivity testing. The wild-type
FAS2 strains produced similar amounts of alcohol as K-1801 did, and the sake brewed by these strains was higher in acidity with higher malate, succinate, and acetate content than that brewed by K-1801. These strains produced less ethyl caproate and much more isoamyl acetate than K-1801 did. Of the ten wild-type
FAS2 strains, we selected one with characteristics(with the exception of aromatic components)that were almost identical to K-1801 and designated it as GL-11. We then performed sake-brewing tests using K-1801 and GL-11 in various proportions. The weight loss in the sake mash as a result of fermentation by each strain was almost identical, and the proportion of both strains was maintained until day 22. Few differences were observed in taste components like organic acids. However, each sake mash had a wide variety of aromatic components such as ethyl caproate. Sensory evaluation indicated similar tastes but different aromas, especially for ethyl caproate. These results suggested that brewing with GL-11 and K-1801 could be used to change the balance of the aromatic components of sake without changing its taste.
View full abstract