G. Ciafardini et al., HYDROLYSIS OF OLEUROPEIN BY LACTOBACILLUS-PLANTARUM STRAINS ASSOCIATED WITH OLIVE FERMENTATION, Applied and environmental microbiology, 60(11), 1994, pp. 4142-4147
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.