Lactic acid bacteria (LAB) are a key element in the dairy industry. The gene products encoded by the plasmids of LAB carry out fermentation. To date, many successful plasmid isolation studies have been conducted with Escherichia coli, Staphilococcus, Streptococcus, Salmonella, Listeria and many strains of LAB. However, since LAB comprise a conglomerate of seven different genera, each with its own physiological and morphological characteristics, and produce a large amount of exopolysaccharide coat, it is extremely difficult to obtain plasmids by conventional methods. A field isolate of lactobacillus known as Lactobacillus salivarius M7 was utilized to obtain plasmids by all known techniques. A modified technique was optimized from the methodologies of Klaenhammer (1983) and Burger et al. (1994). The plasmids obtained with this technique were easily separated into a cleaner and clearer upper phase. There was no need to perform cesium chloride centrifugation, and RNA remnants were totally eliminated. Plasmids obtained with this technique can safely be used in further molecular biological techniques, including sequencing and cloning.

Lactic acid bacteria (LAB) are a key element in the dairy industry. The gene products encoded by the plasmids of LAB carry out fermentation. To date, many successful plasmid isolation studies have been conducted with Escherichia coli, Staphilococcus, Streptococcus, Salmonella, Listeria and many strains of LAB. However, since LAB comprise a conglomerate of seven different genera, each with its own physiological and morphological characteristics, and produce a large amount of exopolysaccharide coat, it is extremely difficult to obtain plasmids by conventional methods. A field isolate of lactobacillus known as Lactobacillus salivarius M7 was utilized to obtain plasmids by all known techniques. A modified technique was optimized from the methodologies of Klaenhammer (1983) and Burger et al. (1994). The plasmids obtained with this technique were easily separated into a cleaner and clearer upper phase. There was no need to perform cesium chloride centrifugation, and RNA remnants were totally eliminated. Plasmids obtained with this technique can safely be used in further molecular biological techniques, including sequencing and cloning.