Samples of panettone sourdoughs manufactured in an industrial bakery located in Japan were investigated. The sourdough starter called mother sponge was imported from Italy and propagated continuously in Japan. According to traditional practice in Italy, panettone sourdoughs were prepared. Microflora was composed of Yeast (10⁶-10⁷cfu/g) and LAB (10⁷-10⁸cfu/g). All the fermentation process, predominant yeasts has the feature of no maltose fermentation and no growth at 37°C. Predominant LAB fermented maltose and has requirement of Tween 80 for growth. DNA-DNA hybridization data exhibited they were Candida milleri and Lactobacillus sanfranciscensis. Furthermore L. sanfranciscensis forming L-lactate was isolated from panettone sourdough. And lactate dehydrogenases took part in isomer of lactate produced by them. It was confirmed that the native microflora of the panettone mother sponge was successfully preserved in Japan.