The present invention provides a process for producing
yeast excellent in
cell productivity and
gene manipulation of which is easy, being added with nutritional requirement by disrupting only a specific
gene, and a transformant thereof. Moreover, the present invention also provides a process for producing a
gene expression product, particularly a polyhydroxyalkanoic acid.In the present invention,
yeast in which a plurality of genes is disrupted is produced using the
homologous recombination. Moreover, a transformant is obtained by introducing a plurality of
enzyme genes involved with polyhydroxyalkanoic acid synthesis such as a polyhydroxyalkanoic acid synthase gene and an
acetoacetyl CoA reductase gene into said gene-disrupted
yeast. Furthermore, said transformant is cultured, copolyesters comprising a polyhydroxyalkanoic acid are efficiently accumulated within the cells, and a
polymer is harvested from the cultured product.