Characteristics of Lactic Acid Bacteria Isolated from Bread-Dough, Compressed-Yeast and Active Dry-Yeast

Abstract

Lactic acid bacteria were isolated at the level of 10⁶ in one gram of the dough using the isolation medium containing 20ppm of cycloheximide. There was no change in the bacterial count during dough-fermentation for 4 hours. Raw materials were investigated to demonstrate the source of many lactic acid bacteria found in bread-dough. As the result, respectable number of lactic acid bacteria were detected in compressed-yeast or active dry-yeast, which are added to bread-dough as fermentation starters. Lactic acid bacteria of 10⁸ to 10¹⁰ cells were counted from each one gram of different 7 samples of compressed-yeast, and 10² to 10⁶ cells from each one gram of 6 samples of active dry-yeast, of which two samples are domestic and the others are imported products. Lactic acid bacteria isolated from bread-dough and 13 samples of yeast-product were identified as Lactobacillus plantarum, Lactobacillus casei, Lactobacillus cellobiosus, Lactobacillus brevis, and Bacillus coagulans. Almost all lactic acid bacteria isolated from bread-dough and compressed-yeast samples had a strong bioaction, that is, ability of acid formation from glucose by fermentation. Therefore, it could be sufficiently considered that in a present bread lactic acid bacteria contributed to its flavor, taste and texture as well as yeast.