Anti-Quorum Sensing Activity of Argentinean Honey and Effect of pH on Main Flavonoids

In this study, the anti-QS activity of regional floral honey from the southeast region of Argentina was investigated using the bacterial model Chromobacterium violaceum. In addition, the anti-QS activity of quercetin, myricetin and luteolin was evaluated in an acidic medium. Two of the tested honey samples had the capacity to exert a notable anti-QS effect on C. violaceum. The effect of quercetin on the anti-QS activity at pH 5.8 was higher than myricetin and luteolin. The results obtained from the identification of quercetin, myricetin and luteolin of the honey extracts by High-Performance Liquid Chromatography (HPLC) showed that quercetin was the main flavonoid followed by myricetin and luteolin. It was observed that honey with high values of quercetin and high value of free acidity, exerted a greater effect on the inhibition of QS. Thus, we can conclude that an umbral value of pH seems to be necessary to increase the anti-QS activity of quercetin.Fil: Chiappe, Cristina Susana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata; Argentina. Universidad Nacional de Mar del Plata. Facultad de Cs.exactas y Naturales. Departamento de Química. Cátedra de Bromatologia; ArgentinaFil: Iurlina, Miriam Ofelia. Universidad Nacional de Mar del Plata. Facultad de Cs.exactas y Naturales. Departamento de Química. Cátedra de Bromatologia; ArgentinaFil: Saiz, Amelia Ivone. Universidad Nacional de Mar del Plata. Facultad de Cs.exactas y Naturales. Departamento de Química. Cátedra de Bromatologia; Argentin

Degradación del Pesticida Clorpirifós por Bacterias Ácido-Lácticas

Los pesticidas organofosforados (OPPs) son uno de los grupos de pesticidas químicos empleados actualmente en agricultura y que contribuyen en más del 36% al total del mercado mundial. El clorpirifós (CF) es el pesticida organofosforado más utilizado en Argentina. Los OPPs son compuestos neurotóxicos y la contaminación de la tierra, aguas superficiales y alimentos representa un potencial riesgo para la salud. Se ha demostrado que las Bacterias Acido Lácticas (BAL) son capaces de degradarlos a partir de mecanismos seguros y métodos económicos. El objetivo del presente estudio fue investigar la biodegradación del CF por BAL. Leuconostoc mesenteroides fue aislada a partir de muestras de origen frutihortícolas, utilizando MRS (De Man, Rogosa y Sharpe) como medio de aislamiento. La cepa fue identificada a partir de su taxonomía por microscopia óptica y mediante las pruebas API CH-50 (Biomériux). La cepa Lactobacillus fermentum (ATCC 9338) fue adquirida de Medica-Tec S.R.L. La degradación del CF se estudió incubando cada BAL en caldo MRS (24 h, 35°) en presencia del pesticida (1,2 mg L-1) monitoreando su concentración a 0, 6, 12 y 24 h. Simultáneamente se realizaron controles de crecimiento por el método de recuento en placa empleando agar MRS. La extracción y purificación del OPP se realizó por cromatografía en columna utilizando sílica-gel y sulfato de sodio como fase estacionaria y hexano como eluyente. La cuantificación del CF se efectuó a través de cromatografía gaseosa (Shimadzu CGMSQP2010 ULTRA-AOC20I) con detección por espectrometría de masas. Los resultados de los ensayos de contacto de ambas cepas manifestaron un impacto positivo en la degradación del CF evidenciado por sus constantes de degradación. La degradación de los OPPs por BAL sigue una cinética de pseudo primer orden. Las cepas L. mesenteroides y L.fermemtum, mostraron una taza de degradación del 97% y 57%, respectivamente, en tanto sus constantes cinéticas fueron 0,1318 h-1 y 0,0178 h-1 . En cuanto a la evolución de la población bacteriana durante el período del ensayo, el recuento de L. mesenteroides se incrementó durante las primeras 6 h (de 105 a 108 UFC mL-1) y luego permaneció aproximadamente constante. El recuento de L. fermentum se mantuvo constante (105 UFC mL-1) al comienzo y se incrementó en 3 órdenes de magnitud, durante las últimas 18 h del estudio. Paralelamente se llevó a cabo un ensayo control, sin BAL, que no mostró variaciones en la concentración del CF. Según los resultados obtenidos, Leuconostoc mesenteroides resultó más eficiente para la biodegradación de CF, asegurando una disminución de la concentración de 97 %.Fil: Pardini, Agustina. Universidad Nacional de Mar del Plata. Facultad de Ciencias Exactas y Naturales. Departamento de Química; ArgentinaFil: Pegoraro, César Nicolás. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones Biológicas. Universidad Nacional de Mar del Plata. Facultad de Ciencias Exactas y Naturales. Instituto de Investigaciones Biológicas; ArgentinaFil: Iurlina, Miriam O.. Universidad Nacional de Mar del Plata. Facultad de Ciencias Exactas y Naturales. Departamento de Química; ArgentinaFil: Saiz, Amelia I.. Universidad Nacional de Mar del Plata. Facultad de Ciencias Exactas y Naturales. Departamento de Química; ArgentinaXXI Congreso Latinoamericano y del Caribe de Ciencia y Tecnología de Alimentos. XVII Congreso Argentino de Ciencia y Tecnología de AlimentosBuenos AiresArgentinaAsociación Argentina de Tecnólogos Alimentario

Death kinetics of Escherichia coli in goat milk and Bacillus licheniformis in cloudberry jam treated by ohmic heating

In recent years, the world’s food industry has focused increasing attention on electrical techniques of food processing. Ohmic heating is one of these techniques that can be considered as a high temperature short time and a purely bulk heating method, having potential applications in processes such as blanching, evaporation and pasteurization in the food industry. However such technology would have to assure the microbiological safety obtained by the conventional cooking methods. Concerning this, the influence of heat treatment by ohmic and conventional technology on death kinetic parameters (D and z values) of Escherichia coli ATCC® 25922 was studied in goat milk. In ohmic treatment lower D values were obtained (D60ºC = 4.2 min, D63ºC = 1.9 min, D65ºC = 0.86 min) as compared to conventional treatment (D63ºC = 3.9 min, D65ºC = 3.5, D67ºC = 2.8 min, D75ºC = 1.5 min). The increase of temperature required for a ten fold decrease in D value was also lower in the ohmic inactivation (z = 8.4 ºC) comparing with the conventional inactivation (z = 23.1 ºC). The death kinetics for Bacillus licheniformis ATCC® 14580 spores in cloudberry jam were also studied under both types of heat inactivation (ohmic and conventional) and similar conclusions were drawn for the D values; lower D values were also obtained for ohmic treatment (D70ºC = 57.1 min, D75ºC = 25.2 min, D80ºC = 7.2 min) as compared to conventional treatment (D70ºC = 85.3 min, D75ºC = 51.0, D80ºC = 18.1 min, D85ºC = 6.0 min, D90ºC = 1.6 min). However, between the z values obtained for those treatments (z ohmic = 11.1 ºC and z conventional = 11.4 ºC) the differences were not significant. In general the results of present work indicate that the ohmic heating provides quicker death kinetics. This opens the perspective for shorter, less aggressive treatments

Comparative study of the physicochemical and palynological characteristics of honey from Melipona subnitida and Apis mellifera

Twenty-four samples of Apis mellifera honey and twenty-four samples of Melipona subnitida (Jandaira) honey were collected in the northeast of Brazil. Moisture, hydroxymethylfurfural, free acidity, insoluble solids in water, diastase activity, ashes, electrical conductivity, proteins, lipids, total carbohydrates, energy and sugars were the parameters analysed. The efficiency of the qualitative tests (Fiehe’s test, Lugol’s reaction, Lund’s reaction) was tested. Pollen types and the corresponding plant species were identified in all samples (3 in Apis and 1 in Melipona). Apis mellifera honey samples demonstrated parameters in accordance with the Brazilian Legislation, while the Melipona subnitida honey samples displayed moisture (24.80%) and diastase activity (null) in discordance with the established by the regulation for Apis mellifera honeys. Apis honey samples presented higher values of electric conductivity (284.00 lS cm 1) than the obtained from the Jandaira honey samples (102.77 lS cm 1) as well as a darker colour (26.67 mmPfund) when compared with Jandaira honey (7.00 mmPfund). The concentration of the glucose, fructose and sucrose was higher in the Apis honeys than in the Jandaira honey. The characteristics of the two types of honey were very different, highlighting the need of developing specific legislation for stingless bees’ honey

Effect of Prosopis sp. honey on the growth and fermentative ability of Pediococcus pentosaceus and Lactobacillus fermentum

Honey is widely known for having antimicrobial and antioxidant activity. These abilities are attributed to honey hydrogen peroxide (H2O2) and polyphenols. Polyphenols also exert beneficial effect on some species of lactic acid bacteria (LAB). In this study, we evaluate the effect of Prosopis sp. honey on the growth and fermentative activity of Pediococcus pentosaceus and Lactobacillus fermentum. Prosopis sp. honey was found to be an important source of phenolic compounds, especially flavonoids, being their average content superior to other honeys. LAB assessed in this study exhibited different responses to the presence of honey. P. pentosaceus was able to develop in concentrations of honey up to 25% (w/v), whilst L. fermentum showed high sensitivity, being affected both growth and fermentative activity. However, as a result of LAB fermentative capacity, the total phenolic and flavonoid content present in 6.5% (w/v) honey solutions was increased, improving the antioxidant activity of this system.Fil: Nutter, Julia. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Mar del Plata. Facultad de Ciencias Exactas y Naturales. Departamento de Química; ArgentinaFil: Fritz, Rosalia. Universidad Nacional de Mar del Plata. Facultad de Ciencias Exactas y Naturales. Departamento de Química; ArgentinaFil: Iurlina, Miriam Ofelia. Universidad Nacional de Mar del Plata. Facultad de Ciencias Exactas y Naturales. Departamento de Química; ArgentinaFil: Saiz, Amelia Ivone. Universidad Nacional de Mar del Plata. Facultad de Ciencias Exactas y Naturales. Departamento de Química; Argentin

Actividad antimicrobiana de mieles del sudeste de la provincia de Buenos Aires frente a Escherichia coli Antimicrobial activity of honey against Escherichia coli

En este trabajo se estudió la sensibilidad de Escherichia coli frente a mieles mediante diferentes técnicas de evaluación de la actividad antimicrobiana. Empleando mieles del sudeste de la provincia de Buenos Aires en concentraciones de 0, 1, 5, 10, 25 y 50% (p/v) se analizó la actividad antimicrobiana de este producto natural frente a Escherichia coli ATCC 25922. La concentración inhibitoria mínima (CIM) se determinó por el test de dilución en serie, en medio líquido (caldo Mueller-Hinton y caldo Mac Conkey). La concentración bactericida mínima (CBM) se evaluó en agar nutritivo y en agar Mac Conkey. Además, se midió la actividad antibacteriana total por el método de difusión en agar en placa. Se observó una reducción del crecimiento promedio del 96% en caldo Mueller-Hinton y del 90% en caldo Mac Conkey, coincidiendo con CIMs de 50 y 25% (p/v), respectivamente. Para las concentraciones evaluadas, en agar nutritivo no se observó acción bactericida, mientras que en agar Mac Conkey se obtuvo una CBM promedio de 25% (p/v). Con el método de difusión en agar en placa, todas las mieles al 50% (p/v) inhibieron el crecimiento de E. coli y una de ellas presentó actividad aún a concentraciones menores (25, 10 y 5% p/v). Las diferentes metodologías resultaron adecuadas para medir la magnitud de la actividad antibacteriana y mostraron que las mieles son activas frente a E. coli a concentraciones de 25 y 50% (p/v). Los métodos de dilución en caldo Mueller-Hinton y de difusión en agar en placa arrojaron valores de inhibición concordantes.This study assessed the susceptibility of Escherichia coli to the antimicrobial activity of honeys by different techniques. Honeys used were from the southeast region of Buenos Aires province. In order to evaluate antimicrobial activity against Escherichia coli ATCC 25922, solutions containing 0, 1, 5, 10, 25 and 50% (w/v) of honey were prepared. Liquid media (Mueller-Hinton and Mac Conkey broths) were used to assess the Minimal Inhibitory Concentration (MIC) by the serial dilution test. The minimal bactericidal concentration (MBC) was determined by counting on nutritive and Mac Conkey agar. In addition, for the evaluation of total antibacterial activity, the agar diffusion method was used. A reduction of microbial growth of 96% in Mueller-Hinton broth and of 90% in Mac Conkey broth by honey solutions containing 50% and 25% (w/v), was respectively observed. The bactericide action of honey in nutritive agar proved negative. The MBC value in Mac Conkey agar was 25% (w/v) of honey. The methods used for measuring the antibacterial activity in the present work were adequate to prove that honeys are active against E. coli at 25 and 50% (w/v) concentrations. The results obtained by the dilution method with Mueller- Hinton broth and the agar diffusion method were both concordant

Microstructural and conformational changes of gluten proteins in wheat-rye sourdough

Changes in the microstructure and secondary structure of sourdough gluten proteins were studied. Four strains of lactic acid bacteria (LAB) were used in fermentations, Lactobacillus delbrueckii subsp. bulgaricus (LB), Lactobacillus fermentum (LF), Lactobacillus plantarum (LP), and Pediococcus pentosaceus (PP). LAB fermentative profiles were performed by potenciometric measurements, microstructural analyses by scanning electron microscopy (SEM), and conformational changes by Raman spectroscopy. Gluten proteins experienced different degree of depolymerisation into defined microstructures, as fibril networks and laminar-like structures, and their occurrence was associated to an increase in β-sheets structures. These changes were dependent upon the distinctive acidifying kinetics of each strain. Gluten proteins of LF and LP sourdough were preferably arranged into laminar structures, and, in both cases, parallel β-sheet was the predominant conformation. Meanwhile for LB and PP sourdough, the development of three-dimensional fibril networks prevailed and it was accompanied by an increase of antiparallel β-sheets. LAB fermentative activity also lead to modifications in disulphide bonds and in the microenvironment concerning aromatic amino acids.Fil: Nutter, Julia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata; Argentina. Universidad Nacional de Mar del Plata. Facultad de Ciencias Exactas y Naturales. Departamento de Química; ArgentinaFil: Saiz, Amelia Ivone. Universidad Nacional de Mar del Plata. Facultad de Ciencias Exactas y Naturales. Departamento de Química; ArgentinaFil: Iurlina, Miriam Ofelia. Universidad Nacional de Mar del Plata. Facultad de Ciencias Exactas y Naturales. Departamento de Química; Argentin

Effect of honey phenolic extract on biofilm formation by Pediococcus pentosaceus and Lactobacillus fermentum

Today, there is an increasing trend to supplement food with phenolic compounds due to the beneficial effect on health. Lactic acid bacteria (LAB) have been shown to form protective biofilms in food industry. However, surrounding condition, such as additives play a significant role in biofilm formation. The aim of this study was to investigate the influence of honey phenolic extract (HPE) on biofilm formation (BF) of Pediococcus pentosaceus and Lactobacillus fermentum. To this end, optimal BF was tested under different environmental conditions, such as pH and cultivation time. Micro-titer plate assay was performed to assess biofilm-forming abilities. In addition, FT-IR spectroscopy and scanning electron microscopy (SEM) were used to monitor the changes in bacterial membrane composition and biofilm morphology. It was observed that the addition of HPE at 0.094 mg/mL reduced BF of L. fermentum and P. pentosaceus by 28% and 15%, respectively. However, BF of P. pentosaceus remained constant as the concentration of phenolic compounds increased. Micrographs of P. pentosaceus revealed a dense production of extracellular polymeric substances that contributed to the bacterial tolerance against phenolic compounds. Band shifts corresponding to COC ring vibrations, confirmed that exopolysaccharides constitute part of P. pentosaceus biofilm. On the other hand, higher concentrations of HPE were found to disrupt biofilm formation by L. fermentum, resulting in loosely associated clusters.Fil: Chiappe, Cristina Susana. Universidad Nacional de Mar del Plata. Facultad de Ciencias Exactas y Naturales. Departamento de Química; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata; ArgentinaFil: Iurlina, Miriam Ofelia. Universidad Nacional de Mar del Plata. Facultad de Ciencias Exactas y Naturales. Departamento de Química; ArgentinaFil: Saiz, Amelia Ivone. Universidad Nacional de Mar del Plata. Facultad de Ciencias Exactas y Naturales. Departamento de Química; Argentin