[Construction of yeast fusants of directly transform starch into ethanol]

To obtain strains that are able to efficiently produce ethanol directly from starchy material, we have used the protoplast fusion technique to construct hybrids between Saccharomyces cerevisiae and Candida tropicalis. The isolation of fusants used a selective system by a irreversible biochemical inhibitor-Iodoacetic Acid(ID), and the fusion frequency was 9.2 x 10(-6). The cell size and DNA content of the fusants were determined. Through testing some productive properties such as specific growth rate, saccharification ability, ethanol tolerance and the activities of alpha-amylase, saccharogen amylase, we selected two fusants--F-1 and F-5. They were more superior and their ethanol production came up to 8.8% and 11.5%.