Abstract: The objective of this study was to separate Leuconostoc from traditional fermented soybean paste and to analyze their prebiotic properties. A total of 56 samples of naturally fermented soybean paste were collected from six regions in northeast China. We separated the suspected strains from these samples using the spread plate method, identified their morphological characteristics, physiological and biochemical characteristics, and analyzed their 16S rRNA gene sequences. The acid and bile salt tolerance of Leuconostoc strains were compared. As a result, we obtained 118 strains of lactic acid bacteria suspected of being Leuconostoc. Six of these were confirmed as Leuconostoc, three of which were identified as Leuconostoc lactis while the remaining three were identified as Leuconostoc mesenteroides subsp. mesenteroides. Among these Leuconostoc strains, strain FX6 had the best prebiotic potential and its survival rate was 85.16% after 3 h incubation at pH 3.0 and was up to 96.07% after 6 h incubation with 0.3 g/100 mL bile salt. Therefore, strain FX6 can be used for further research and industrial applications. The mechanism of action of FX6 in the soybean paste fermentation process still needs to be elucidated further.

Key words: soybean paste, 16S rRNA gene, Leuconostoc, probiotics