Lactose-utilizing hybrid strain derived from Saccharomyces cerevisiae and Kluyveromyces lactis by protoplast fusion.

Protoplast fusion was carried out between a sake brewer's yeast strain, Saccharomyces cerevisiae Kyokai 7, and a lactose utilizing yeast strain, Kluyveromyces lactis T396. A stable hybrid, PN 13, which was selected from the many resultant fusants, showed physiologically complemented traits with respect to sugar utilization, vitamin requirements and so on. Biochemical investigations also revealed that fusant PN 13 was an intermediate hybrid between the parental strains. In glucose and lactose media, moreover, the fusant grew and produced ethanol at higher rates than K. lactis T396.