Characterization of β-glucosidase of Lactobacillus plantarum FSO1 and Candida pelliculosa L18 isolated from traditional fermented green olive

Yahya Rokni,Houssam Abouloifa,Reda Bellaouchi,Ismail Hasnaoui,Sara Gaamouche,Zahra Lamzira,Riadh B.E.N Salah,Ennouamane Saalaoui,Nabil Ghabbour,Abdeslam Asehraou

doi:10.1186/s43141-021-00213-3

Abstract

BackgroundOleuropein, the main bitter phenolic glucoside responsible for green olive bitterness, may be degraded by the β-glucosidase enzyme to release glucose and phenolic compounds. ResultsLactobacillus 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. ConclusionsL. 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.

Highlights

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
The strains FSO1 and L18 demonstrated an absence of OLP spot, and the appearance of HT and 2 other components (C1 and C2), with retention factor (Rf) values of 0.37, 0.48, and 0.54, respectively. These results indicate the production of β-glucosidase and esterase by L. plantarum FSO1 and C. pelliculosa L18, and it can be due to the acidification of the medium resulting from the fermentation of glucose released from the degradation of oleuropein by β-glucosidase [29], leading to the elimination of oleuropein and accumulation of hydroxytyrosol
The present study was focused on the characterization of β-glucosidase of the strains L. plantarum FSO1 and C. pelliculosa L18, isolated from traditional fermented green olive

Summary

Introduction

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. Oleuropein, an O-glycosylated compound composed of D-glucose β (1-4) linked to aglycone, is reported to be hydrolyzable by the β-glucosidase enzyme, releasing Dglucose and aglycone [1, 3]. The latter is subsequently hydrolyzed with esterase to simpler phenolic compounds, namely hydroxytyrosol and elenolic acid [1, 4]. This hydrolysis plays an important role in enhancing the lactic fermentation process of olives by, providing. The β-glucosidase enzymes are widespread in microorganisms, and their genes of production can differ in strains of the same species [9]

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