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- Monitoring C. vulgaris Cultivations Grown on Winery Wastewater Using Flow CytometryPublication . Lopes da Silva, Teresa; Silva, Thiago; França, Bruna Thomazinho; Ribeiro, Belina; Reis, AlbertoABSTRACT: Winery wastewater (WWW), if released untreated, poses a serious environmental threat due to its high organic load. In this study, Chlorella vulgaris was cultivated in diluted WWW to assess its suitability as a culture medium. Two outdoor cultivation systems-a 270 L raceway and a 40 L bubble column-were operated over 33 days using synthetic medium (control) and WWW. A flow cytometry (FC) protocol was implemented to monitor key physiological parameters in near-real time, including cell concentration, membrane integrity, chlorophyll content, cell size, and internal complexity. At the end of cultivation, the bubble column yielded the highest cell concentrations: 2.85 x 106 cells/mL (control) and 2.30 x 106 cells/mL (WWW), though with lower proportions of intact cells (25% and 31%, respectively). Raceway cultures showed lower cell concentrations: 1.64 x 106 (control) and 1.54 x 106 cells/mL (WWW), but higher membrane integrity (76% and 36% for control and WWW cultures, respectively). On average, cells grown in the bubble column had a 22% larger radius than those in the raceway, favouring sedimentation. Heterotrophic cells were more abundant in WWW cultures, due to the presence of organic carbon, indicating its potential for use as animal feed. This study demonstrates that FC is a powerful, real-time tool for monitoring microalgae physiology and optimising cultivation in complex effluents like WWW.
- Fractionation of macroalgae carbohydrates using hydrothermal and dilute inorganic salt pretreatments to produce oligosaccharides and furansPublication . Martins, Pedro L.; Andrade, Cristiana; Duarte, Luís; Reis, Alberto; Pereira, Helena; Carvalheiro, FlorbelaABSTRACT: Furans are among the most important compounds derived from biomass, providing conversion pathways for sustainable alternatives to petroleum-based fuels and materials. Furfural, 5-hydroxymethylfurfural (5-HMF), and 5-methylfurfural (5-MF) are furans that can be obtained by carbohydrate dehydration under acidic conditions at elevated temperature and pressure. One of the mechanisms to produce these compounds from lignocellulosic materials relies on prior fractionation of biomass carbohydrates and further dehydration catalysis. However, this is a costly and technically challenging method and it would be advantageous to develop a one-pot conversion mechanism that facilitates simultaneous biomass fractionation and conversion to furans. Ulva lactuca is an alga that has the advantage of being lignin-free and rich in glucose, rhamnose, and xylose, which are ideal for producing 5-HMF, 5-MF, and furfural, respectively. The high diversity of sugar constituents is also relevant for the production of added-value oligosaccharides. Catalysis with inorganic salts has been reported as a successful tool for biomass upgrading to furans when combined with hydrothermal pretreatments, and could provide a cheap and environmentally friendly one-step methodology for furan production. This study therefore aimed to investigate the effect of hydrothermal and dilute acid pretreatments, as well as treatment with inorganic salt solutions (ferric chloride, ferric nitrate, and aluminium nitrate) on U. lactuca biomass to produce oligosaccharides, monosaccharides, and furans (furfural, 5-HMF, and 5-MF). These methods resulted in a maximum sugar solubilization of 65% in non-salt-assisted hydrothermal pretreatments and 84% in salt-assisted hydrothermal pretreatments, with inorganic salt catalysis also resulting in 100% xylose, 36% glucose, and 46% rhamnose conversion to the respective furans.