This invention relates to the structural gene for the membrane-bound aldehyde dehydrogenase derived from microorganisms belonging to the genus Acetobacter, said structural gene having a molecular size of about 3.6 Kb and having a restriction enzyme cleavage map as shown in FIG. 1; to a plasmid containing said structural gene; to an acetic acid bacterium transformed by said plasmid; and to an acetic acid fermentation process using said transformant.