The use of sourdoughs in bread baking in Vietnam has recently been increased but little is known about microorganisms in those sourdoughs. This study was to assess changes in pH value and microbial density of a sourdough from bread flour (BF) and a sourdough from all-purpose flour (AF) during propagation. The results showed that the type of flour did not cause a significant difference in pH changes, but it could contribute to the distinct levels of lactic acid bacteria (LAB) and yeast in the two sourdoughs. The BF sourdough gained proper maturation in 15 days when it reached pH of 3.69, 1.3 x 10⁹ CFU g^-1 LAB and 7.4 x 10⁸ CFU g^-1 yeast. Meanwhile, the AF sourdough had lower levels of LAB and yeast (3.9 x 10⁸ CFU g^-1 and 1.0 x 10⁸ CFU g^-1, respectively). Sequencing analysis revealed the presence of Lactobacillus plantarum in the BF sourdough on the 10^th and 15^th days of the propagation process. Wickerhamomyces anomalus was found on the 10^th day while Saccharomyces cerevisiae was detected on the 15^th day. This sourdough can be used in further studies to assess the benefits of sourdough in bread baking.