To construct a system for producing an industrially useful substance through gene recombination by utilizing characteristics of a yeast, it is intended to provide a yeast in which a specific gene alone has been disrupted and to which auxotrophy is imparted. A yeast strain in which ADE1 gene has been disrupted is constructed by homologous recombination with a chromosomal DNA by using an ADE1 gene fragment encoding phosphoribosylaminoimidazole succinocarboxamide synthase (EC6.3.2.6) of Candida maltosa . Then, this disrupted strain is transformed by a gene expression cassette containing a biodegradable polyester synthase gene and the obtained transformant is cultured to thereby produce biodegradable polyester.
