Lactobacillus plantarum: Effect of a protective biofilm on the surface of olives during storage

Abstract The aim of the present study was to investigate the effect of Lactobacillus plantarum adhesion to the surface of olives during storage through studying the interaction between the surfaces of the olives and L. plantarum. The results showed that the total number of adherent L. plantarum increased exponentially from 1.2 × 106 to 1.3 × 108 cfu/g. Images obtained using environmental scanning electron microscopy (ESEM) after 4 days of storage revealed that the olive surface was covered with a uniform and compact biofilm constituted of L. plantarum and yeast. Physicochemical analysis of surface of L. plantarum revealed that it was hydrophilic (Giwi > 0 mJ/m2). The surface of the olives also appeared to be hydrophilic (Giwi = 3.28 mJ/m2). The electron-donor characteristics of the surfaces of L. plantarum and olive were γ− = 53.1 mJ/m2 and γ− = 28.1 mJ/m2, respectively. The formation of a protective biofilm of L. plantarum increased the hydrophilicity (from 3.28 to 46.14 mJ/m2) and the electron-donor capacity (from 28.1 to 67.2 mJ/m2) of the olive surface by 1 day of storage. Analysis of the impact of the biofilm that formed on the surface of the olives during storage showed a reduction in the content of undesirable planktonic microorganisms, such as fungi, which could have occurred due to competition for nutrients and oxygen or modifications in the physicochemical properties of the olives. Thus, coating the surface of olives with a natural material, such as L. plantarum, may be a first step in developing strategies to prevent their microbial colonization.

Use of green fluorescent protein to monitor Lactobacillus plantarum in the gastrointestinal tract of goats

The experiment aimed to specifically monitor the passage of lactobacilli in vivo after oral administration. The green fluorescent protein (GFP) gene was cloned downstream from the constitutive p32 promoter from L. lactis subsp. cremoris Wg2. The recombinant expression vector, pLEM415-gfp-p32, was electroporated into Lactobacillus plantarum (L. plantarum) isolated from goat. Green fluorescent protein (GFP) was successfully expressed in L. plantarum. After 2 h post-administration, transformed Lactobacillus could be detectable in all luminal contents. In the rumen, bacteria concentration initially decreased, reached the minimum at 42 h post-oral administration and then increased. However, this concentration decreased constantly in the duodenum. This result indicated that L. plantarum could colonize in the rumen but not in the duodenum.

Evaluación de bacteriocinas como medio protector para la biopreservación de la carne bajo refrigeración / Evaluation of bacteriocines as protective means for the biopreservation of refrigerated meat

The objective was to evaluate shelf-life extension of fresh beef meat applying crude extract of bacteriocines produced by a native strain of Lactobacillus plantarum LPBM10. Fillets of rib (longissimus dorsi) were stocked during 12 days at 3° C and analyzed by means of microbiology analysis, pH, texture, weight loss and sensorial. Significant differences were found among treatments for psychrotrophics and fecal coliforms, being better the treatment with crude bacteriocin extract that had germicide effect. Fecal coliforms were inhibited by the crude bacteriocin extract during most of the period. The mesophilic count didn’t present difference among treatments. The pH changes and the weight loss present statistical variations among treatments and between days. Cutting force diminished during storage time in all treatments improving meat tenderness without presenting significant difference. The appearance, color and aroma diminished the acceptance value as the storage time advanced.

El objetivo del presente trabajo fue evaluar la extensión de la vida útil de carne refrigerada mediante la aplicación de extracto crudo de bacteriocinas producido por Lactobacillus plantarum LPBM10. Se utilizaron filetes de solomo redondo (longissimus dorsi) almacenados durante 12 días a 3º C y analizados por medio de análisis microbiológicos, pH, textura, pérdidas de peso y sensoriales. Se encontraron diferencias significativas entre los tratamientos para psicrotrófilos y coliformes totales, resultando mejor el tratamiento con extracto crudo de bacteriocinas que tuvo efecto bactericida. Los coliformes fecales también fueron inhibidos por el extracto crudo de bacteriocinas. Los cambios de pH y pérdida de peso presentan variaciones estadísticas entre tratamientos y entre días. La fuerza de corte disminuyó durante el tiempo de almacenamiento en todos los tratamientos mejorando la terneza de la carne sin presentar diferencia significativa. La apariencia, color y aroma disminuyeron el valor de aceptación a medida que avanzo el tiempo.