HYDROLYSIS OF OLEUROPEIN BY LACTOBACILLUS-PLANTARUM STRAINS ASSOCIATED WITH OLIVE FERMENTATION

Oleuropein (Chemical Abstracts Service registry number 32619-42-4), a bitter-tasting secoiridoid glucoside commonly found in leaves of the o live tree as well as in olives (Olea europaea L.), was found to be hyd rolyzed by the beta-glucosidase (EC 3.2.1.2.1) produced by oleuropeino lytic Lactobacillus plantarum-type strains. Three strains, designated B17, B20, and B21, were isolated from the brine of naturally ripe oliv es not treated with alkali. These strains were rod-shaped forms, groan at a pH 3.5 limit, and tolerated 1% oleuropein and 8% NaCl in the gro wth medium. The beta-glucosidase produced hydrolyzed 5-bromo-4-chloro- 3-indolyl-beta-D-glucopyranoside as well as oleuropein. The presence o f 2% glucose in the medium inhibited activity by 40 to 50%, depending on the bacterial strain. Chromatographic analysis of the trimethylsily l derivatives of the products obtained after 7 days of incubation at 3 0 degrees C of strain B21 showed all the hydrolysis products of oleuro pein, i.e., aglycone, iridoid monoterpen, and 3,4-dihydroxyphenylethan ol (hydroxytyrosol). Oleuropein and its aglycone after 21 days of incu bation decreased to trace levels with the simultaneous increase in con centration of beta-3,4-dihydroxyphenylethanol.