Percorrer por autor "Maciel, Cláudia"
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- Development of a flow-based system for the determination of protein content in microbiological samplesPublication . Oliveira, Ricardo; Maciel, Cláudia; Vidigal, Susana S. M. P.; Teixeira, Paula; Rangel, António O. S. S.
- Development of a novel phagomagnetic-assisted isothermal DNA amplification system for endpoint electrochemical detection of Listeria monocytogenesPublication . Maciel, Cláudia; Silva, Nádia F. D.; Teixeira, Paula; Magalhães, Júlia M. C. S.The hitherto implemented Listeria monocytogenes detection techniques are cumbersome or require expensive non-portable instrumentation, hindering their transposition into on-time surveillance systems. The current work proposes a novel integrated system resorting to loop-mediated isothermal amplification (LAMP), assisted by a bacteriophage P100–magnetic platform, coupled to an endpoint electrochemical technique, towards L. monocytogenes expeditious detection. Molybdophosphate-based optimization of the bacterial phagomagnetic separation protocol allowed the determination of the optimal parameters for its execution (pH 7, 25 °C, 32 µg of magnetic particles; 60.6% of specific capture efficiency). The novel LAMP method targeting prfA was highly specific, accomplishing 100% inclusivity (for 61 L. monocytogenes strains) and 100% exclusivity (towards 42 non-target Gram-positive and Gram-negative bacteria). As a proof-of-concept, the developed scheme was successfully validated in pasteurized milk spiked with L. monocytogenes. The phagomagnetic-based approach succeeded in the selective bacterial capture and ensuing lysis, triggering Listeria DNA leakage, which was efficiently LAMP amplified. Methylene blue-based electrochemical detection of LAMP amplicons was accomplished in 20 min with remarkable analytical sensitivity (1 CFU mL−1). Hence, the combined system presented an outstanding performance and robustness, providing a 2.5 h-swift, portable, cost-efficient detection scheme for decentralized on-field application.
- Electrostatic assembly of anti-listeria bacteriophages on a self-assembled monolayer of aminoundecanethiol: film morphology, charge transfer studies, and infectivity assaysPublication . Fernandes, Paula M. V.; Maciel, Cláudia; Teixeira, Paula; Pereira, Carlos M.; Campina, José M.The integration of bacteriophages, a particular class of viruses that specifically infect bacteria and archaea, in biosensors for the monitoring of pathogens in foods and beverages is highly desirable. To this end, an increasing focus has been set on the exploration of covalent and physical methods for the immobilization of phages on solid surfaces. This work investigates the electrostatic assembly of tailed phages, specifically anti-Listeria monocytogenes P100 phages, on an ultrathin self-assembled monolayer (SAM) of 11-amino-1-undecanethiol (AUT). The cationic properties of AUT may allow for the electrostatic capture of P100 in a capsid-down fashion, thereby exposing the specific receptor-binding proteins on their tails to the corresponding pathogens in the analytical samples. The morphology and charge transfer behavior of the assembled films were studied with atomic force microscopy, scanning electron microscopy and electrochemical techniques. These methods provided valuable insights into the orientation of the phages and the relevant role of the pH. Biological plaque assays revealed that the immobilized phages remain active towards the target bacterium. Overall, this research portrays SAMs of amino-akylthiols as a valid platform for the oriented immobilization of bacteriophages on surfaces for electroanalytical purposes.
- Exploiting potential probiotic lactic acid bacteria isolated from Chlorella vulgaris photobioreactors as promising vitamin B12 producersPublication . Ribeiro, Mónica; Maciel, Cláudia; Cruz, Pedro; Darmancier, Helena; Nogueira, Teresa; Costa, Margarida; Laranjeira, Joana; Morais, Rui M. S. C.; Teixeira, PaulaLactic acid bacteria (LAB) have been documented as potential vitamin B12 producers and may constitute an exogenous source of cobalamin for the microalga Chlorella vulgaris, which has been described as being able to perform vitamin uptake. Hence, there is an interest in discovering novel B12-producing probiotic LAB. Therefore, the purpose of the current work was to perform a phenotype–genotype analysis of the vitamin B12 biosynthesis capacity of LAB isolated from C. vulgaris bioreactors, and investigate their probiotic potential. Among the selected strains, Lactococcus lactis E32, Levilactobacillus brevis G31, and Pediococcus pentosaceus L51 demonstrated vitamin B12 biosynthesis capacity, with the latter producing the highest (28.19 ± 2.27 pg mL−1). The genomic analysis confirmed the presence of pivotal genes involved in different steps of the biosynthetic pathway (hemL, cbiT, cobC, and cobD). Notably, P. pentosaceus L51 was the only strain harboring cobA, pduU, and pduV genes, which may provide evidence for the presence of the cobalamin operon. All strains demonstrated the capability to withstand harsh gastrointestinal conditions, although P. pentosaceus L51 was more resilient. The potential for de novo cobalamin biosynthesis and remarkable probiotic features highlighted that P. pentosaceus L51 may be considered the most promising candidate strain for developing high-content vitamin B12 formulations.
- High hydrostatic pressure and pediocin PA-1 as a synergistic system to listeria monocytogenes inactivation in fermented meat sausagePublication . Maciel, Cláudia; Komora, Norton; Ferreira, Vânia; Saraiva, Jorge; Castro, Sónia Marília; Teixeira, Paula
- High-pressure processing and lytic bacteriophage cocktail phageguard S as a synergistic hurdle system towards salmonella inactivation in egg whitePublication . Maciel, Cláudia; Campos, Ana; Komora, Norton; Pinto, Carlos A.; Brandão, Teresa R. S.; Saraiva, Jorge A.; Teixeira, PaulaSalmonella spp. still represents a major public health concern as the etiological agent of foodborne diarrhoeal illnesses. Salmonella Enteritidis is the most common serovar associated with non-typhoidal salmonellosis in the United States and Europe, through the ingestion of raw, undercooked eggs or egg-derived food products. The consumption pattern has changed worldwide, towards a growing demand for minimally processed foods. The association of emerging technologies with conventional antimicrobial agents has been scarcely exploited as a feasible multi-hurdle decontamination approach. The purpose of the present work was to develop a novel non-thermal technology through the combination of mild high pressure processing (HPP, 300 MPa) with the bacteriophage PhageGuard S towards a 4-strain Salmonella cocktail inactivation in egg white. A preliminary set of experiments allowed to establish the most adequate parameters to be employed in the proposed system. Concerning the HPP (200 to 600 MPa) resistance pattern of thirteen food and clinical Salmonella strains belonging to serovars Enteritidis, Typhimurium and Senftenberg, a prominent intrastrain heterogeneity was observed and as expected, higher pressure magnitudes elicited a lower survivability. Regarding the impact of the pressure processing on the egg white viscoelastic profile, it was found that from 400 MPa onwards the complex viscosity and elastic modulus increased noticeably. The second part of the work sought to investigate the decontamination potential of the proposed treatment. In the challenge assays performed in egg white comprising a high bacterial load (107 CFU mL-1), HPP per se was not able to accomplish a prominent bactericidal effect, whilst the combination with the bacteriophage elicited Salmonella inactivation to values below the detection limit. The association of the two hurdles was determined to be a synergism. Moreover, a scarce impact on the physical features of egg white – color, foaming capacity and rheological properties - was observed throughout the 7-day refrigerated storage (4ºC). To our knowledge, this is the first study documenting a sustainable non-thermal technology as a suitable alternative to egg white pasteurization since the synergistic system HPP-PhageGuard S accomplished a Salmonella 5- log reduction.
- Merging zones approach in a flow-based platform for the determination of the total protein content in microbiological samplesPublication . Oliveira, Ricardo; Maciel, Cláudia; Vidigal, Susana S. M. P.; Teixeira, Paula; Rangel, António O. S. S.
- Non-thermal approach to Listeria monocytogenes inactivation in milk: the combined effect of high pressure, pediocin PA-1 and bacteriophage P100Publication . Komora, Norton; Maciel, Cláudia; Pinto, Carlos A.; Ferreira, Vânia; Brandão, Teresa R. S.; Saraiva, Jorge M. A.; Castro, Sónia Marilia; Teixeira, PaulaNon-thermal food processing and replacement of chemical additives by natural antimicrobials are promising trends in the food industry. The objective of the present work was to evaluate the effect of a process which combines mild high hydrostatic pressure – HHP (200 and 300 MPa, 5 min, 10 °C), phage Listex™ P100 and the bacteriocin pediocin PA-1 as a new non-thermal process for destruction of Listeria monocytogenes (104 CFU mL−1 or 107 CFU mL−1) in milk. For inoculum levels of 104 CFU mL−1, HHP combined with phage P100 eliminated L. monocytogenes immediately after pressurization. When L. monocytogenes was inoculated at levels of 107 CFU mL−1, a synergistic effect between phage P100, pediocin PA-1 and HHP (300 MPa) on the inactivation of L. monocytogenes was observed during storage of milk at 4 °C. For non-pressure treated samples inoculated with phage or pediocin or both, L. monocytogenes counts decreased immediately after biocontrol application, but regrowth was observed in a few samples during storage. Phage particles were stable during refrigerated storage for seven days while pediocin PA-1 remained stable only during three days. Further studies will have to be performed to validate the findings of this work in specific applications (e.g. production of raw milk cheese).
- Non-thermal synergistic approach to Listeria monocytogenes inactivation in milk: the combined effect of high pressure and bacteriophage P100Publication . Komora, Norton; Maciel, Cláudia; Ferreira, Vânia; Saraiva, Jorge; Castro, Sónia Marília; Teixeira, Paula
- Processing slime from snail (Helix aspersa maxima): a preliminary study on the effect on microbial loadPublication . Teixeira, Raquel; Barbosa, Joana; Albano, Helena; Maciel, Cláudia; Silva, Joana; Saraiva, Jorge A.; Castro, Sónia M.; Teixeira, PaulaSlime from earth snails (Helix aspersa maxima) is a sub-product often used in the cosmetic industry. Due to its origin, a decontamination process ought to be considered. After exposure to UV radiation, no significant (P > 0.05) reduction of the initial microbial load of slime was observed, while treated at 60 °C, a decrease of 4.0 log CFU∙mL-1 was obtained (when compared to non-treated slime). A similar reduction was attained for pressurized (500 MPa) slime. The sequential combination of temperature and pressure treatment had a similar effect (P > 0.05) on the microbial load when compared to 400 MPa (30 min), but the reduction was higher when compared to the less intense treatments (60 °C, 15 min; 400 MPa, 15 min). Overall, the results suggest that pressure ( 400 MPa) is a promising technology for processing snail slime, which can have positive effects on its microbial load, for further use in the cosmetic industry