RESUMEN Selección de cepas de bacterias ácido lácticas que degradan oleuropeína aisladas en la fermentación de aceitunas verdes marroquíes.Un total de 177 cepas de bacterias ácido lácticas (LAB) fueron aisladas en las primeras etapas de la fermentación de aceitunas verdes marroquíes Picholine, incluyendo Lactobacillus plantarum (44.63%), Lactobacillus pentosus (25.99%), Lactobacillus brevis (9.61%) y Pediococcus pentosaceus (19.77%). Todos los aislados fueron evaluados mediante su tolerancia a extractos de hojas de olivo y oleuropeína. La mayoría de los aislados (85,3%) degradaron oleuropeína, cuando fueron evaluados usando oleuropeína o 5-Bromo-4-cloro-3-indolil β-D-glucuronido (X-Gluc) como sustrato. La capacidad de biodegradación de las cepas seleccionadas para cada especie fue confirmada mediante análisis por HPLC.PALABRAS CLAVE: Aceituna -Bacteria ácido láctica -Fermentación -β-glucosidasa -Oeluropeína. SUMMARY Selection of oleuropein-degrading lactic acid bacteria strains isolated from fermenting Moroccan green olives.A total of 177 strains of lactic acid bacteria (LAB) were isolated from early-stage Moroccan Picholine green olive fermentation, including Lactobacillus plantarum (44.63%), Lactobacillus pentosus (25.99%), Lactobacillus brevis (9.61%) and Pediococcus pentosaceus (19.77%). All the isolates were screened for their tolerance to olive leaf extract and oleuropein. Most of the isolates (85.3%) were found able to degrade oleuropein, when evaluated by either oleuropein or 5-Bromo-4-chloro-3-indolyl β-D-glucuronide (X-Gluc) as substrates. The biodegradation capacity of the selected strains of each species was confirmed by HPLC analysis. KEY-WORDS:Fermentation -β-glucosidase -Lactic acid bacteria -Oleuropein -Olive.

SUMMARY:The control of the spontaneous fermentation process of un-debittered Moroccan Picholine green olives was undertaken basing the inoculation with two lactobacilli strains (Lactobacillus plantarum S175 and Lactobacillus pentosus S100). These strains, previously selected in our laboratory for their oleuropein-degrading capacity, were inoculated in olives brined at 5% of NaCl, and then incubated at 30 °C. The physico-chemical parameters (pH, free acidity, reducing sugars, sodium chloride, oleuropein and its hydrolysis products), and the microbiological parameters (mesophilic aerobic bacteria, coliforms, Staphylococcus, lactic acid bacteria and yeasts and moulds), were regularly analyzed during the fermentation time. The results obtained showed the effectiveness of the lactic acid bacteria strains to develop suitable oleuropein biodegradation and controlled lactic fermentation processes more than the un-inoculated olives (control). This result was confirmed by the rapid elimination of coliforms and staphylococcus, the accumulation of hydroxytyrosol as a result of oleuropein biodegradation, and a drastic reduction in spoiled olives with good quality fermented olives. KEYWORDS:Fermentation; Green olives; Lactobacillus; Oleuropein; Starter RESUMEN: Fermentación controlada de aceitunas verdes picholine marroquí mediante cepas de lactobacilos degradantes de oleuropeína. Se llevó a cabo el control del proceso de fermentación espontánea de aceitunas verdes sin desamargar picholine marroquí basado en la inoculación con dos cepas de lactobacilos (Lactobacillus plantarum S175 y Lactobacillus pentosus S100). Estas cepas, seleccionadas previamente en nuestro laboratorio por su capacidad de degradar a la oleuropeína, se inocularon en las aceitunas en salmuera al 5 % de NaCl, y después se incubaron a 30 °C. Los parámetros físico-químicos (pH, acidez libre, reducción de azúcares, cloruro sódico, oleuropeína y sus productos de hidrólisis) y los parámetros microbiológicos (bacterias aerobias mesófi-las, coliformes, estafilococos, bacterias lácticas y levaduras y mohos), fueron analizados regularmente durante el tiempo de fermentación. Los resultados obtenidos mostraron la eficacia de las cepas de bacterias lácticas para desarrollar una adecuada biodegradación de la oleuropeina y los procesos de fermentación láctica controlados más que en el caso de las aceitunas no inoculadas (control). Estos resultados fueron confirmados por la rápida eliminación de coliformes y estafilococos, por la acumulación de hidroxitirosol como resultado de biodegradación de la oleuropeína, y por ladrástica reducción de aceitunas estropeadas y por la buena calidad de las aceitunas fermentadas.

The objective of this work is to study the oleuropein (OLP) biodegradation by a strain of Lactobacillus plantarum FSO175 under conditions (pH 4.5, NaCl 5% and glucose 1%), during 7 days of incubation at 30 °C, in modified MRS broth containing OLP as carbon source. The results obtained, by HPLC analyses, showed that the biodegradation of OLP by L. plantarum FSO175, is accompanied with increase of hydroxytyrosol (HT) content and acidity values. The yields of OLP degradation and HT accumulation are depending on carbon sources, stress conditions and time of incubation. So that, the drastic reduction in OLP biodegradation, obtained at pH 6.7 (trial B), decreased significantly (p

Background Oleuropein, the main bitter phenolic glucoside responsible for green olive bitterness, may be degraded by the β-glucosidase enzyme to release glucose and phenolic compounds. Results Lactobacillus plantarum FSO1 and Candida pelliculosa L18 strains, isolated from natural fermented green olives, were tested for their β-glucosidase production and activity at different initial pH, NaCl concentrations, and temperature. The results showed that strains produced extracellular and induced β-glucosidase, with a molecular weight of 60 kD. The strains demonstrated their biodegradation capacity of oleuropein, associated with the accumulation of hydroxytyrosol and other phenolic compounds, resulting in antioxidant activity values significantly higher than that of ascorbic acid. The highest production value of β-glucosidase was 0.91 U/ml obtained at pH 5 and pH 6, respectively for L. plantarum FSO1 and C. pelliculosa L18. The increase of NaCl concentration, from 0 to 10% (w/v), inhibited the production of β-glucosidase for both strains. However, the β-glucosidase was activated with an increase of NaCl concentration, with a maximum activity obtained at 8% NaCl (w/v). The enzyme activity was optimal at pH 5 for both strains, while the optimum temperature was 45 °C for L. plantarum FSO1 and 35 °C for C. pelliculosa L18. Conclusions L. plantarum FSO1 and C. pelliculosa L18 strains showed their ability to produce an extracellular and induced β-glucosidase enzyme with promising traits for application in the biological processing of table olives.