Characterization of Leuconostoc Isolates from Commercial Mixed Strain Mesophilic Starter Cultures

In order to understand better the properties of mixed strain mesophilic starter cultures, 155 Leuconostoc mesenteroides ssp. cremoris and Leuconostoc tactis isolates were purified from three commercial cultures. Isolates were divided into groups based on plasmid content. All strains contained between 2 and 6 plasmids, ranging in size from 1 to 30 MDa One group of Leuc. tactis and five groups of Leuc. mesenteroides ssp. cremoris were obtained. The sensitivity to bacteriophage and pattern of DNA fragments when total genomic DNA was digested with the restriction enzyme EcoRI showed that strains within a plasmid group are related. Thus, plasmid analysis is as valid a technique for strain identification of Leuconostoc as it is for other dairy lactic acid bacteria. Each culture contained at least two different groups of Leuconostoc.