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Research Project
Center for Mediterranean Bioresources and food
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Publications
Magnetite nanoparticles functionalized with propolis against methicillin resistant strains of Staphylococcus aureus
Publication . EL-GEUNDOUZ, Soukaina; Lyoussi, Badiaa; Lourenço, João P.; Rosa Da Costa, Ana; Miguel, Maria; Barrocas Dias, Cristina; Manhita, Ana; Jordao, Luisa; Nogueira, Isabel; Faleiro, Maria Leonor
Magnetite nanoparticles (MNPs) have been evaluated for inhibiting microbial growth and biofilm formation. In this study the effect of the nanocomposite Moroccan propolis extract / MNPs acting against methicillin resistant strains of Staphylococcus aureus (MRSA) was evaluated. Chemical composition of propolis was established by pyrolysis coupled to gas chromatography and mass spectrometry method (pyrolysis GC/MS). MNPs were obtained through the co-precipitation method. The fabricated nanostructure was characterized by X-ray Diffraction (DRX), Transmission Electron Microscopy (TEM), and Fourier Transform-Infrared Spectroscopy (FTIR).
TEM of MNPs provided a particle average size of 15 nm, FTIR spectral analysis enabled a fast way of identification of MNPs, attesting the occurrence of the different combinations. The use of MNPs loaded with propolis and the antibiotic chloramphenicol at Minimum Inhibitory Concentration (MIC) value inhibited the bacterial growth of MSSA (methicillin susceptible strain of S. aureus) and MRSA strains. After the treatment with MNPs-OA-P-CLo nanocomposite (MNPs with oleic acid, propolis and chloramphenicol), the disruption of the bacterial cell was observed by TEM. The combination of propolis and chloramphenicol in free form at MIC value largely impaired both MSSA and MRSA strains as, after 2 h of treatment, no viable cells of MRSA 2 and MRSA 16 were recovered. Hence, the results elucidated a new antibacterial nanocomposite synthesis, for possible applications as prospective nanoantibacterial agents or drug carriers.
Photorelease of incarcerated caged acids from hydrophobic coumaryl esters into aqueous solution
Publication . Kamatham, Nareshbabu; Mendes, Débora C.; Silva, José P. da; Givens, Richard S.; Ramamurthy, V.
Photolysis of aqueous solutions of carboxylic acid esters of 7-(methoxycoumaryl)-4-methanol included within the capsule made up of two molecules of octaacid released the acids in water. The trigger 7-(methoxycoumaryl)-4-methyl chromophore remains within octaacid either as the alcohol or as an adduct with the host octaacid through a hydrogen abstraction process. The method established here offers a procedure to release hydrophobic acid molecules in water at will in a timely manner with light. In addition, the system offers an unanticipated opportunity to probe the mechanistic dichotomy of a diradicaloid intermediate expressing both radical and ionic behavior when generated by coumarylmethyl ester photolysis in a hydrophobic environment.
Membrane fatty acids and physiological disorders in cold-stored ‘Golden Delicious’ apples treated with 1-MCP and calcium chloride
Publication . Antunes, Maria Dulce; Guimarães, Ana Clara; Gago, Custódia; Guerreiro, Adriana; Panagopoulos, Jorge; Vilas Boas, Eduardo; Miguel, Maria da Graça
The present research intents to study skin fatty acids and physiological disorders developed during cold storage in ‘Golden Delicious’ apples treated with 1-MCP and calcium. Harvested fruits were treated with calcium chloride (Ca), 1-MCP (MCP), Ca + MCP or no treatment (control) and then subjected to cold storage at 0.5 °C for 6 months. Fatty acids’ composition, malondialdehyde (MDA) and the physiological disorders bitter pit (BP), superficial scald and diffuse skin browning (DSB) were measured at harvest and after storage plus 7 days of shelf-life at room temperature ≈22 °C. Palmitic acid decreased and linoleic acid increased over time, while oleic and stearic acids had few changes. Generally, unsaturated/saturated fatty acids and MDA increased over the storage period. Treatment with Ca showed that, at the end of the experiment, the lowest MDA values and the highest unsaturated/saturated fatty acids ratio were mainly due to higher linoleic and lower palmitic acids concentrations, which are coincident with less severe BP. There was no clear correlation between the measured fatty acids (palmitic, linoleic, oleic and stearic), unsaturated-to-saturated fatty acids ratio or MDA with chilling skin physiological disorders. Further research is needed to clarify the changes in membrane properties and the effect of some treatments in response to chilling injury during storage.
Betalains in some species of the amaranthaceae family: A review
Publication . Miguel, Maria
Natural pigments are largely distributed in the plant kingdom. They belong to diverse groups, with distinct biochemical pathways. Betalains with colours that range from yellow to red-violet can de divided into two main subgroups: betaxanthins and betacyanins. These types of pigments are confined into 13 families of the order Caryophyllales and in some genera of higher fungi (Amanita muscaria, Hygrocybe and Hygrophorus). The Amaranthaceae family includes diverse genera in which betalains are present: Alternanthera, Amaranthus, Beta, Chenopodium, Celosia and Gomphrena. The biosynthesis of betalains and their general biological properties were reviwed in the present work. In addition, the types of betalains present in some species of the aforementioned genera, their stability and production, as well as biological attributes, were reviewed.
Entomopathogenic fungi from Algarve region (Portugal): studies on their natural occurrence in the soil and multitrophic interactions that shape their biocontrol potential
Publication . Bueno Pallero, Francisco Ángel; Neto, Luís Mascarenhas; Dionísio, Lídia Pó Catalão; Herrera, Raquel Campos
The entomopathogenic fungi (EPF) are well-known beneficial soil organisms naturally
occurring in the soil. Learning about their natural distribution in representative habitats and their
interactions with other soil organisms can establish the best ecological scenario for the activity as
biocontrol agents. Also, the co-formulation of two entomopathogens with plant-based products can be
an affordable approach for farmers. With the Algarve region (Portugal) as a research frame, the objectives
of this PhD thesis were: (1) to investigate the natural distribution of EPF in soils from the Algarve in four
habitats (oak, pines, palmettoes, and citrus groves) and two soil eco-regions (calcareous and noncalcareous),
(2) to evaluate whether the presence of entomopathogenic nematodes (EPN) or/and
nematophagous fungi (NF) can affect the biocontrol potential of EPF, and (3) to investigate the impact
of plant-based oil adjuvants on biocontrol activity of single or combined EPF and EPN, and the impact
of time and temperature in the EPN survival and activity.
Firstly, we combined three isolation methods (fresh soil, dry soil, and selective media) to
investigate the natural EPF distribution in the Algarve, using traditional and molecular tools for the
identification. We established the assemblage of the EPF with the soil properties and EPN by using
multivariate analysis. Second, we investigated the multitrophic interactions in single (EPF, EPN, NF),
dual (EPN+EPF, EPF+NF, EPN+NF) and triple (EPN+EPF+NF) combinations of one EPF (Beauveria
bassiana), one EPN (Steinernema feltiae), and two NF (Arthrobotrys musiformis and Purpureocillium
lilacinum). Three different fungal applications (contact with mycelia, immersion, and injection)
simulated different timing of fungal arrival. Also, we evaluated the interaction in the mycelia growth
between EPF and NF species. We tested the impact on biocontrol of two plant-based oils (coconut and
olive oils) when combined the EPF B. bassiana and the EPN Steinernema colombiense. Also, the
viability and virulence of EPN incubated at five temperatures (4, 8, 14, 20, and 24°C) and five incubation
times (1, 3, 7, 14, and 21 days) with both plant-based adjuvants was also evaluated.
The distribution of EPF in the Algarve region was not driven by botanical group or by ecoregion
(calcareous versus non-calcareous). Five EPF species were identified, with B. bassiana as the dominant
EPF (34% of the localities), followed by Fusarium solani (26%), and F. oxysporum (14%), both reported
as EPF for the first time in Portugal. The species P. lilacinus (8%) and Metarhizium anisopliae (2%)
were minority. Soil pH, organic matter, and Mg content explained most of the variability of the EPF
community and EPN species-specific distribution. Second, we observed that EPF B. bassiana limited
both NF species growth and viceversa. The EPF B. bassiana dominated triple-interaction when mycelia
were exposed. The EPN S. feltiae dominated the triple-interaction in immersion exposure. The NF A.
musiformis caused larval mortality if vectored inside the host. Finally, the plant-based oils tested wer compatible with the EPF and EPN. The combination of EPN+EPF produced an additive effect. EPN
survival was higher in coconut than olive oil and water mixtures up to 7 days at 4ºC. Moreover, olive oil
supported higher larval mortality caused by EPN than coconut oil at 4-20ºC and 14 days. Overall, this
thesis provides new insights on the interactions occuring in the soil that can modulate their activity of
EPF as biological control agents.
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Funding agency
Fundação para a Ciência e a Tecnologia
Funding programme
6817 - DCRRNI ID
Funding Award Number
UID/BIA/04325/2013