Abstract: Using the traditional separation and purification method, we isolated a total of 435 strains suspected of being lactic acid bacteria from 20 samples of naturally fermented pickles collected from 4 different regions of northern China. We used 16S rDNA sequence homology analysis for species identification. The results showed that all the isolates belonged to lactic acid bacteria, including 394 strains of Lactobacillus modestisalitolerans, L. sakei, L. coryniformis, L. plantarum, L. brevis and L. delbrueckii, 38 strains of Enterococcus, 2 strains of Leuconostoc mesenteroides, and 1 strain of Pediococcus siamensis. The composition of microbial flora in pickle samples from different regions was different. Among them, the most abundant microbial flora was found in samples from Liaoning and Henan provinces, consisting of six species. The number of acid-producing bacteria found in pickle samples from Jilin was the highest. Nine of these strains were found to have a strong ability to produce acid over 24 h, and their survival rates were above 70% after 3 h of exposure to simulated gastric juice (pH 2.0). This study provides a theoretical guidance and technological support for the quality improvement of traditional pickles and the development of high-quality strain resources.

Key words: naturally fermented pickles; lactic acid bacteria; microbial population; acidogenic properties; acid resistance