Characterization and electrotransformation of Lactobacillus plantarum and Lactobacillus paraplantarum isolated from fermented vegetables

Aims of the study were to characterize two Lactobacillus plantarum-related strains, Lact. plantarum and Lactobacillus paraplantarum isolated from fermented vegetables and, for their potential use as starter strains, compare their growth in various food matrices. Species-level identification of the strains belonging to the Lact. plantarum group was performed by multiplex-PCR with species-specific primers and generation of distinct genotypic profiles was carried out by PFGE-based DNA-fingerprinting. Growth profiles were determined in various food and feed matrices. Compared to Lact. plantarum, Lact. paraplantarum reached higher cell densities in all plant-based matrices and MRS broth. On the contrary to the good growth in plant-based matrices and MRS, poor growth was observed in unprocessed milk. Supplemented lactose did not improve the growth of either tested strain, while predigestion of milk proteins with Lactobacillus helveticus or addition of casitone proved to be an effective means to enhance growth. To find out the applicability of molecular methods, the strains were transformed with replicative plasmids by electroporation. To our knowledge, this is a first report of the electrotransformation of Lact. paraplantarum with a recombinant plasmid.