Molecular characterization of lactic acid bacteria isolated from industrially fermented Greek table olives

A total of 145 lactic acid bacteria (LAB) isolates have been recovered from fermented table olives and brine and characterized at strain level with molecular tools. Pulsed-Field Gel Electrophoresis (PFGE) of ApaI macrorestriction fragments was applied for strain differentiation. Species differentiation was based either on Denaturing Gradient Gel Electrophoresis (PCR-DGGE) (black olives) or on restriction analysis of the amplified 16S rRNA gene (PCR-ARDRA) (brine and green olives). Species identification was based on sequence analysis of 16S rRNA gene. When the data were insufficient to resolve the species level of the isolates, specific multiplex PCR assays targeting the recA or tuf genes were employed. From 145 LAB isolates, 71 different strains were recovered from fermented olive and brine samples; 17 strains were assigned to Leuconostoc mesenteroides, 51 were grouped in Lactobacillus plantarum group (including 13 L. plantarum, 37 Lactobacillus pentosus, 1 Lactobacillus paraplantarum), 2 Lactobacillus paracasei subsp. paracasei and 1 Leuconostoc pseudomesenteroides. L. plantarum was recovered mainly from green olive fermentation, whereas in black olives the main species identified were L. pentosus and Ln. mesenteroides). These observations reveal that olives are a highly diverse ecosystem regarding the presence of LAB, which may affect the quality of the final fermented product.