Isolation of Lactic Acid Bacteria from Environmental Samples and Screening of Fermentation Capacity

Abstract

Lactic acid bacteria are a kind of probiotics widely distributed in nature. Because of their versatility and adaptability, lactic acid bacteria have attracted wide attention in many fields such as medicine, agriculture and industry. Lactic acid bacteria are widely found in various environments. Therefore, environmental samples such as water, soil and various plant surfaces are important sources of lactic acid bacteria. The purpose of this experiment was to isolate, identify and screen the fermentation ability of lactic acid bacteria in environmental samples. After the lactic acid bacteria in environmental samples were isolated and purified by plate streaking method, MRS solid medium was used to screen out the strains with soluble calcium ring or green color from environmental soil and environmental water sources. Finally, the screened strains were identified by morphological observation, physiological and biochemical tests and 16 S rRNA gene sequence alignment. The species of lactic acid bacteria can be determined by comparing the 16 S rRNA sequence with the sequence in the database. The results showed that multiple strains of lactic acid bacteria were successfully screened from environmental samples. Strains X-1-1 and X-1-2 belong to Lactobacillus plantarum, strains X-4-1 and X-4-2 belong to Lactobacillus brevis, strains X-6-1 and X-6-2 belong to Lactobacillus fermentum, strains X-7-1 and X-7-2 belong to Enterococcus faecalis, strains X-10-1 and X-10-2 belong to Lactobacillus paracasei. The phylogenetic tree constructed by MEGA showed the genetic relationship and genetic differences between different strains. The results showed that strain X-1-1 and strain X-1-2 had the strongest genetic relationship, and the sequence alignment results showed that both strains belonged to Lactobacillus plantarum. Through this study, the separation process, molecular identification method and screening process of lactic acid bacteria were systematically understood, and it was expected to provide ideas for the separation, screening and molecular identification of lactic acid bacteria.