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676 results on '"Crespo, João G."'

21. Sustainable production of nanoemulsions by membrane-assisted nanoemulsification using novel aroma-based hydrophobic deep eutectic solvents for enhanced antifungal activities

Author

Fundação para a Ciência e a Tecnologia (Portugal), Ministério da Ciência, Tecnologia e Ensino Superior (Portugal), Ministerio de Ciencia, Innovación y Universidades (España), Agencia Estatal de Investigación (España), Ministerio de Ciencia e Innovación (España), Mondal, Suchintan, Syed, Usman T., Pinto, E., Leonardo, Inês C., Romero, Pilar, Gaspar, Frédéric B., Barreto Crespo, M. T., Sebastián, Víctor, Crespo, João G., Brazinha, Carla, Fundação para a Ciência e a Tecnologia (Portugal), Ministério da Ciência, Tecnologia e Ensino Superior (Portugal), Ministerio de Ciencia, Innovación y Universidades (España), Agencia Estatal de Investigación (España), Ministerio de Ciencia e Innovación (España), Mondal, Suchintan, Syed, Usman T., Pinto, E., Leonardo, Inês C., Romero, Pilar, Gaspar, Frédéric B., Barreto Crespo, M. T., Sebastián, Víctor, Crespo, João G., and Brazinha, Carla

Abstract

Hydrophobic deep eutectic solvents (DESs), a recent class of green solvents, offer 100% atom economy, low cost, potential biodegradability, negligible toxicity and promising bioactivities. In this work, novel aroma-based therapeutic hydrophobic DESs were prepared and dispersed in aqueous media as nanoemulsions to potentiate biomedical applications, where polar media is encountered. A reusable microengineered stainless-steel isoporous membrane was fabricated by laser drilling technique. Three hydrophobic DESs, namely DES A (menthol and vanillin), DES B (menthol and raspberry ketone), and DES C (thymol and raspberry ketone) were prepared and emulsified in aqueous media by sustainable membrane emulsification technique. The optimised nanoemulsion (DES C-in-water) exhibited a monomodal size distribution with Zavg (size average) of 147 nm and polydispersity index of 0.22. From the application perspective, the formulated DES-in-water nanoemulsions and their constituents were evaluated for their antibacterial properties against Escherichia coli and Staphylococcus aureus. Additionally, antifungal properties of the DES-based emulsions were reported for the first time by testing them against four fungal strains, Aspergillus fumigatus, Candida albicans, Candida krusei, and Trichophyton mentagrophytes. The nanoemulsions were found to be exhibit antimicrobial effect and lesser quantities of individual compounds were needed in nanoemulsified state to show similar effects. Different 1D and 2D NMR techniques were successfully used to investigate the structural orientation and the inter and intramolecular interactions in the DES and emulsion systems, which revealed a probable cause for higher antimicrobial activity of DES C-based emulsions compared to its peers. Lastly, a synergistic effect of the components in nanoemulsions led to enhanced antimicrobial activities.

Published
2024

24. Streamer formation dynamics with mixed bacterial species: Effects of cultivation conditions, hydrodynamics, and species.

Author

Sendekie, Zenamarkos B., Bacchin, Patrice, Lammertink, Rob G. H., and Crespo, João G.

Subjects
MIXED culture (Microbiology), BACTERIAL cultures, ENTEROBACTER, HYDRODYNAMICS, BIOFILMS
Abstract

Most bacterial species synthesize extracellular polymeric substances (EPS) with diverse compositional, structural, and functional characteristics. When under sustained hydrodynamic flow, bacteria form streamers, which are filamentous matrix structures porous in nature. So far, investigations on streamers have been limited to pure culture bacterial species, overlooking the aggregate nature of bacterial flocs and biofilms. The aim of this work is to analyze the effects of the cultivation conditions (controlling the EPS synthesis), the hydrodynamics, and the bacterial species type on streamer formation by pure and mixed culture using microfluidic separators. Enterobacter A47 (EPS-producing bacterium) and Cupriavidus necator (non-EPS producing bacterium) are used for the experimental work. It has been found that the EPS secreted by the bacteria and flow conditions play a very significant role in streamer formation dynamics. Strong flow conditions (i.e., high flow rates and small constrictions with tortuous architecture) favor the fast development of streamers, whereas intermediate flow rates result in sustained growth for longer filtration times, leading to dense streamers. Our analysis confirms that the presence of EPS in the bacterial suspension critically controls streamer formation by forming bacterial aggregates, or flocs, and bridging between different aggregates. We also found that streamer formation is significantly enhanced with mixed bacterial culture, which may be attributed to the symbiotic relationships influencing the concentration and characteristics of EPS and the material behavior in general. [ABSTRACT FROM AUTHOR]

Published
2024
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