Percorrer por autor "Rossetto, Veronica"
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- Culturable yeast diversity associated with industrial cultures of the microalga microchloropsis gaditana and their ability to produce lipids and biosurfactantsPublication . Matos, Madalena; Fernandes, Mónica A.; Costa, Inês; Coelho, Natacha; Santos, Tamara; Rossetto, Veronica; Varela, João; Sá-Correia, IsabelThe marine oleaginous microalga Microchloropsis gaditana (formerly Nannochloropsis gaditana) exhibits a high capacity to thrive in a broad range of environmental conditions, being predominantly utilized as feed in aquaculture. This article reports the characterization of the culturable yeast population present during the scale-up process of M. gaditana cultivation at Necton S.A. facilities, from 5 L flasks until tubular photobioreactors. The 146 yeast isolates obtained, molecularly identified based on D1/D2 and ITS nucleotide sequences, belong to the species Rhodotorula diobovata, R. mucilaginosa, R. taiwanensis, R. sphaerocarpa, Vishniacozyma carnescens, Moesziomyces aphidis, and Meyerozyma guilliermondii. The yeast abundance was found to increase throughout upscaling stages. The yeast populations isolated from microalgal cultures and water samples share phylogenetically close isolates, indicating a possible common source. The impressive high percentage of red yeasts isolated (90%) is consistent with the recognized role of carotenoid pigments in yeast photoprotection. Sixty yeast isolates were tested for lipid (Nile Red staining) and biosurfactant (oil drop dispersion and emulsification index) production. Results revealed that these capacities are common features. Microbial lipids and biosurfactants have promising biotechnological applications. Moreover, biosurfactants can fulfill various physiological roles and provide advantages in natural environments contributing to the promising use of yeasts as probiotics in microalgae production.
- Tailored bacterial co-cultures improve Tisochrysis lutea growth and nutrient profiles under xenic conditions: a new pathway to improve microalgal productionPublication . Santos, Tamara; da Fonseca Simões, Beatriz; Rossetto, Veronica; Pereira, Hugo; Maia, Inês Beatriz; Oliveira, Marta; Esteves Lopes Navalho, João Carlos; Engelen, Aschwin; Varela, JoãoThe marine haptophyte Tisochrysis lutea is a valuable source of high-value compounds, including polyunsaturated fatty acids like docosahexaenoic acid, and pigments (e.g., fucoxanthin). However, high production costs and variability remain major challenges for its large-scale application in aquaculture, pharmaceuticals, and biotechnology industries. Therefore, strategies to enhance biomass production and quality are actively explored. In natural environments, T. lutea establishes mutualistic interactions with bacteria to obtain essential nutrients such as vitamin B12, yet the role of bacteria in industrial cultures remains poorly understood. In this study, 145 bacterial strains were isolated and taxonomically identified from industrial T. lutea cultures, with members of the class Gammaproteobacteria and Actinomycetia being the most prevalent. Forty isolates were screened individually in co-culture with T. lutea revealing strain-specific effects on growth and biochemical composition. Seven beneficial strains were used to design 21 tailored bacterial blends. Several consortia enhanced biomass production (up to 74 %) and increased key bioactive compounds, particularly methylcobalamin (up to 300 %). These findings demonstrate the potential of tailored bacterial consortia to enhance T. lutea productivity and nutritional quality under production-relevant xenic conditions, enabling strategic microbiome modulation for specific industrial goals.
- Understanding new microbial communication systems to combat antimicrobial resistancePublication . Rossetto, Veronica; Galvão, Helena M.; Reen, JerryBacterial biofilms provide an advantageous spatial structure for colonization and cell maintenance as a community. This multicellular behaviour is regulated by a bacterial quorum-dependent mechanism, called the quorum sensing (QS) system that regulates other diverse social behaviours such as toxin production and virulence factors. This mechanism is regulated by signal molecules that regulate intra-specific, inter-specific and inter-kingdom interactions. For these reasons, this mechanism is strongly studied, as well as signalling molecules and analogues, such as alkyl-quinolone based compounds, for the disarming of pathogenic bacteria resistant to multi-drugs that plague public health worldwide. The path to a complete understanding of how this occurs, what are the conditions for such biological responses and what machinery and mechanisms exist for the perception and modulation of these interactions is still far from reaching a conclusion. Therefore, the present work seeks to evaluate compounds against behaviours dependent on the quorum sensing mechanism, as well as the effect of these compounds on the growth of harmful pathogens, such as Pseudomonas aeruginosa and Staphylococcus aureus. Providing information to assist in understanding these microbial interactions, as well as the development of new anti-infectious strategies and the fight against antimicrobial resistance. The tested compounds confirmed activities such as anti-biofilm, anti-swarming and anti-pyocyanin production. Of the twenty-three analogous compounds to the alkyl-quinolones screened thirteen presented some type of interference between the three evaluated phenotypes, five with significant antagonistic activities against P. aeruginosa PA14 and three against staphylococcal strains, such as S. aureus, Staphylococcus haemolyticus and Staphylococcus hominis. Thus, it is concluded that small molecules based on alkyl-quinolones are effective bioactive against QS dependent behaviours and can assist in unravelling microbial communication and its impacts on human society.