Direct utilization of purple sweet potato by sake yeasts to produce an anthocyanin-rich alcoholic beverage

Objective To produce an alcoholic beverage containing anthocyanins that can act as antioxidants and have anticarcinogenic activities and antihypertensive effects. Results High starch-assimilating sake yeast strain of Saccharomyces cerevisiae co-expressing the glucoamylase and α-amylase genes from Debaryomyces occidentalis using the double rDNA-integration system was developed. The new strain grew substantially using 5 % (w/v) purple sweet potato flour as the sole carbon source. Its cell yield reached 14.5 mg ml −1 after 3 days. This value was 2.4-fold higher than that of the parental wild-type strain. It produced 12 % (v/v) ethanol from 20 % (w/v) purple sweet potato flour and consumed 98 % of the starch content in purple sweet potato flour after 5 days of fermentation. Conclusion We have produced a health-promoting alcoholic beverage abundant in anthocyanins from purple sweet potato.