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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.

Biological preservatives are increasingly in demand as an alternative to chemicals, because of consumer’s health and environmental concerns. Lactic acid bacteria isolated from fermented olives, considered as extreme environment, may encompass significant antimicrobial activity against microorganisms involved in foodborne diseases and food spoilage. Three LAB strains (Levilactobacillus brevis S27, Lactiplantibacillus pentosus S42, and Lactiplantibacillus plantarum S62), isolated from fermented olive, were studied for their antimicrobial activity against pathogenic bacteria (Listeria innocua and E. coli) and yeast (Rhodotorula glutinis), involved in foodborne diseases and food spoilage. The microbial culture, cell-free supernatant (CFS) of all LAB strains showed inhibition zone (IZ) values ranges of 26.33-28.83 mm, 14.16-16.33 mm and 10-12.16 mm against R. glutinis, L. innocua and E. coli, respectively. The IZ values ranges obtained with NCFS (neutralized CFS at pH 7) against R. glutinis and L. innocua were respectively of 17.83-20.50 mm and 13.16-14.50 mm, whereas no inhibition was obtained against E. coli. Their bioactive molecules of proteinaceous nature showed that among the four peptide bands obtained, two bands of approximately 42 and 56 kDa are common for the three LAB strains (S27, S42 and S62). Two additional bands of 46 and 89kD are observed in S42 and S27, respectively. The minimum inhibitory concentration of 10-fold concentrated CFS (10xCFS) obtained was 5% against E. coli and 4.5% against L. innocua and R. glutinis. The 10xCFS of Lb. plantarum S62, selected as the most efficient strain against pathogens, demonstrated its effectiveness in decontamination of milk at concentrations of 0.45% (v/v) and 0.5% (v/v) against L. innocua and E. coli. The CFS allowed, at 0.5 mL/piece of 5 cm diameter, a total inhibition of R. glutinis, without affecting the color of Pastilla leaf. The CFS of Lb. plantarum S62 can be used as a bio-preservative against pathogenic bacteria (L. innocua and E. coli) in milk, and against R. glutinis in Pastilla leaf.

The aim of the present study was to evaluate some technological properties and potential probiotic of 14 Lactobacillus strains isolated from brines of natural fermenting Moroccan Picholine green olive. The brine samples, collected from industrial environments, were analyzed for their Physico-chemical and microbiological properties. The Lactobacillus strains were characterized for their technological and physiological properties. The results obtained showed that the olive brines have an average pH of 4.32, an acidity of 0.61% and chloride contents of 6.42%. LAB and yeasts are the most dominant microorganisms in olive brine samples. The selected Lactobacillus (14 strains) showed low resistance to pH 2 and high resistance to bile salts (up to 2%), with values ranges from 1.98%-4.70% and 63.12%-86.48%, respectively. All the Lactobacillus strains displayed high levels of acidification and can produce β-glucosidase, protease, and cellulase in large amounts. The diacetyl production is detected in five Lactobacillus strains.