| Summary: | In this study, the physicochemical properties (pH, acidity, salinity, and soluble protein), bacterial diversities, isoflavone contents, and antioxidant activities of <i>doenjang</i> (fermented soy paste), household <i>doenjang</i> (HDJ), and commercial <i>doenjang</i> (CDJ), were assessed and compared. The values of pH 5.14–5.94 and acidity 1.36–3.03%, indicated a similar level in all doenjang. The salinity was high in CDJ at 12.8–14.6%, and the protein contents (25.69–37.54 mg/g) were generally high in HDJ. Forty-three species were identified from the HDJ and CDJ. The main species were verified to be <i>Bacillus amyloliquefaciens</i> (<i>B. amyloliquefaciens</i>), <i>B</i>. <i>amyloliquefaciens</i> subsp. <i>plantarum</i>, <i>Bacillus licheniformis</i>, <i>Bacillus</i> sp. and <i>Bacillus subtilis</i>. Comparing the ratios of isoflavone types, the HDJ has an aglycone ratio of >80%, and 3HDJ indicates a ratio of isoflavone to aglycone of 100%. In the CDJ, except 4CDJ, glycosides account for a high proportion of more than 50%. The results of antioxidant activities and DNA protection effects were variedly confirmed regardless of HDJs and CDJs. Through these results, it is judged that HDJs have a variety of bacterial species compared to CDJs, and these are biologically active and converted from glycoside to aglycone. Bacterial distribution and isoflavone contents could be used as basic data.
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