The efficiency of Lactiplantibacillus plantarum S61 strain as protective cultures in ground beef against foodborne pathogen Escherichia coli.

The aim of the study was the bio-control effectiveness of the Lactiplantibacillus plantarum S61 strain, isolated from traditional fermenting green olives, against Escherichia coli B805 in ground beef. The bio-control effect of L. plantarum S61 against E. coli B805 was evaluated in ground meat during storage under refrigeration at 4 °C. The results showed that L. plantarum S61 reduced the biomass of pathogenic bacteria (E. coli) in ground meat during 10 days of storage at 4 °C. Moreover, the treatment with L. plantarum S61 has no adverse effect on the sensory properties of ground meat after 10 days of storage at 4 °C. The treatment with L. plantarum S61 and storage at 4 °C effectively decreases the growth and risk of pathogenic bacteria in ground meat and, consequently, increases the product's shelf life. Therefore, the application of L. plantarum S61 during the storage of ground meat beef may help reduce the use of chemical preservatives in meat products. Consequently, L. plantarum S61 can be applied as a bio-control agent against spoilage and pathogenic bacteria in meat and meat products.

Characterization of antimicrobial compounds obtained from the potential probiotic Lactiplantibacillus plantarum S61 and their application as a biopreservative agent.

This work aimed to characterize the antimicrobial compounds obtained from the potential probiotic Lactiplantibacillus plantarum S61, isolated from traditional fermented green olive, involved in their activity against fungi and bacteria responsible for food spoilage and poisonings. Their application as a biopreservative agent was also investigated. The culture of L. plantarum S61 showed substantial antifungal and antibacterial activity against yeasts (Rhodotorula glutinis and Candida pelliculosa), molds (Penicillium digitatum, Aspergillus niger, Fusarium oxysporum, and Rhizopus oryzae), and pathogenic bacteria (Listeria monocytogenes ATCC 19,117, Salmonella enterica subsp. enterica ATCC 14,028, Staphylococcus aureus subsp. aureus ATCC 6538, Pseudomonas aeruginosa ATCC 49,189), with inhibition zones > 10 mm. Likewise, the cell-free supernatant (CFS) of L. plantarum S61 showed an essential inhibitory effect against fungi and bacteria, with inhibition diameters of 12.25-22.05 mm and 16.95-17.25 mm, respectively. The CFS inhibited molds' biomass and mycelium growth, with inhibition ranges of 63.18-83.64% and 22.57-38.93%, respectively. The antifungal activity of the CFS was stable during 4 weeks of storage at 25 °C, while it gradually decreased during storage at 4 °C. Several antimicrobial compounds were evidenced in the CFS of L. plantarum S61, including organic acids, ethanol, hydrogen peroxide, diacetyl, proteins, and fatty acids. The protein fraction, purified by reversed-phase high-performance liquid chromatography (RP-HPLC), demonstrated important antifungal activity, in relation to the fraction with molecular weight between 2 and 6 kDa. L. plantarum S61 and its CFS, tested in apple and orange fruit biopreservation, demonstrated their protective effect against P. digitatum spoilage. The CFS exhibited effectiveness in reducing Salmonella enterica subsp. enterica ATCC 14,028 in apple juice. L. plantarum S61 and/or its bioactive compounds CFS represent a promising strategy for biocontrol against pathogens and spoilage microorganisms in the agro-industry.

Bio-preservation Effect of Probiotic Lactiplantibacillus plantarum S61 Against Rhodotorula glutinis and Listeria monocytogenes in Poultry Meat.

The objective of this work is the study of the antifungal and antibacterial activity of Lactiplantibacillus plantarum S61 strains, isolated from traditional fermenting green olives against Rhodotorula glutinis UMP 22 and Listeria monocytogenes ATCC 19117, and its application in meat as bio-preservative agent. The cell-free supernatant (CFS) of Lpb. plantarum S61 shows high inhibition zones, which are 22.45 ± 0.49 and 17.75 ± 0.35 mm, against Rhodotorula glutinis and Listeria monocytogenes. The minimum fungicidal and bactericidal concentrations of the CFS obtained are 8% (v/v) and 10% (v/v), respectively. The competition assay, realized in liquid medium by co-culture of Lpb. plantarum S61 with Rho Rhodotorula glutinis and L. monocytogenes, led to inhibition percentages of 77.72% and 89.52%, respectively. However, the antimicrobial activity of Lpb. plantarum S61 was revealed a proteinaceous nature. Lpb. plantarum S61 strain allowed the reduction of L. monocytogenes in minced poultry meat during 7 days of storage at 4 °C. In addition, Lpb. plantarum S61 improved the physicochemical and color parameters of poultry minced meat. Lpb. plantarum S61 and/or its antimicrobial compounds can be applied as bio-preservative agent in meat product and food industry.

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

BACKGROUND: Oleuropein, the main bitter phenolic glucoside responsible for green olive bitterness, may be degraded by the ß-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 ß-glucosidase production and activity at different initial pH, NaCl concentrations, and temperature. The results showed that strains produced extracellular and induced ß-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 ß-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 ß-glucosidase for both strains. However, the ß-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 ß-glucosidase enzyme with promising traits for application in the biological processing of table olives.