Protoplast fusion of Saccharomyces and Kluyveromyces to develop thermotolerant ethanol-producing yeast strains

摘要

To develop thermotolerant ethanol producing yeast strains, the protoplasts of Saccharomyces carlsbergensis having good fermentability at 30 deg C and Kluyveromyces marxianus able to grow at 42 deg C were fused. Under the optimal conditions for protoplast formation, the frequency of protoplast formation of S. carlsbergensis was 92-94 percent and that of K. marxianus was 98 percent. Fusion frequency between S. carlsbergensis and K. marxianus was 1.4 X 10~(-6) - 4.8 X 10~(-7). Among the 27 fusants obtained, 6 fusants were able to grow at 42 deg C. While the parental strains produced 3.2-3.4 percent (w/v) ethanol after 3 days from the fermentation medium containing glucose, fusants SK41-4 and SK53-22 produced 5.2 percent (w/v) ethanol in the same condition. The thermotolerance of SK53-22 was not high, but that of SK41-4 was quite high.