Construction of a flocculating yeast for fuel ethanol production.

The expression vector pYX212 harboring FLO1 gene and kanMX gene was transformed into Saccharomyces. cerevisiae ZWA46. The transformant, ZWA46-F2, showed strong and stable flocculation ability during 20 serial batch cultivations. The flocculation onset of the strain is in the early stationary growth phase, not coincident with the glucose depletion in the culture medium. The flocculation ability of the transformant showed no difference with the initial pH ranging from 3.5 to 6.0. Furthermore, the ethanol concentration and other properties of the transformant strain ZWA46-F2 were similar to those of the wild-type strain ZWA46.