This study aims to examine the effects of glucose and NaCl on the ability of an oleuropein degrading strain of Lactobacillus plantarum, strain B21, to grow in the presence of oleuropein, its degradation product, hydroxytyrosol, and p-coumaric acid. Oleuropein (10 g litre−1) and 2 g litre−1 hydroxytyrosol combined with NaCl did not inhibit bacterial growth, whereas 1 g litre−1 p-coumaric acid showed low inhibitory activity. This study also presents that bacterial β-glucosidase and esterase are involved in the breakdown of oleuropein. Oleuropein (10 g litre−1) incorporated in the cultivation medium without glucose was completely degraded to derivative products within 20 days, whereas in the presence of glucose, at concentrations up to 50 g litre−1 β-glucosidase activity was partially inhibited, and 30–70% of oleuropein residual content remained in the cultivation medium. Esterase activity involved in the second step of biodegradation process, was not influenced by glucose. Incorporation of glucose in the growth medium adversely affected the ability of L plantarum to break-down oleuropein. The findings of this study are significant since it could lead to the development of a new biotechnology for removing the bitter principle, oleuropein, from olives replacing the traditional alkali treatment used for debittering olives.
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Marsilio et al. (1998) studied this question.