Selection of strains capable of utilizing D-xylose and cellobiose to produce ethanol by electric field-induced protoplast fusion.

The protoplast fusion between Candida guilliermondii S208 (Arg-) and Saccharomyces cerevisiae 314 was induced by three pulses (18kV/cm, 10 microseconds duration) applied at an interval of 1 s with the model GH-401 Electric Induced Gene Transfer/Cell Fusion System. The frequency of appearance of prototrophic hybrids was 3.6 x 10(-3). Stable fusion products were obtained after continual subculture over 20 times on selected and unselected media. Comparative studies showed that the fusion products were real hybrids of both parents. Two fustants, F-106 and F-308, could ferment both D-xylose and cellobiose to ethanol. The ethanol production of F-106 in the media containing 2% D-xylose or 2% cellobiose were 3.1g/l and 1.05g/l, respectively. The ethanol production of F-308 in the above media were 0.2g/l and 2.8g/l, respectively.