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- Rapid spectrophotometric determination of nitrates and nitrites in marine aqueous culture mediaPublication . Carvalho, A. P.; Meireles, L. A.; Malcata, F. XavierThe spectrophotometric determination of nitrate in sea water broths for cultivation of, say, microalgae is complicated by the frequent presence of nitrite. Two methods - sulphamic/perchloric acid method (also known as Cawse method) and sulphamic acid method - both claimed to be able to eliminate nitrite interference, were tested using a set of standards, but statistical treatment of the results proved their limitations in nitrate quantification. An improved method, based on former published methods for quantification of nitrite and coupled determination of nitrate and nitrite, was designed and tested. This improved method was compared with the reference method (based on use of a cadmium column) using several standards and biological samples of two culture media for microalgae, in different phases of their growth curve. The results thus obtained have demonstrated that there is no statistically significant difference between them at the 5% level. The precision of the method was tested by repeating determinations with three sets of standard mixtures containing nitrate and nitrite. The method proposed has advantages over conventional methods in reduced time of analysis, as well as high precision and accuracy, so it may be a good alternative for determination of nitrite and nitrate in marine aqueous media.
- Potencial biotecnológico das microalgasPublication . Carvalho, A. P.; Meireles, L. A.; Malcata, F. X.; Oliveira, G.; Raposo, M. F.; Morais, R.
- Antimicrobial activity and lipid profile of seaweed extracts from the North Portuguese coastPublication . Mendes, M.; Pereira, R.; Pinto, I. Sousa; Carvalho, A. P.; Gomes, A. M.Seaweeds or marine macroalgae are a potential renewable resource in the marine environment and can represent a source of new natural compounds for human nutrition. This experimental work focused on the selection of a suitable extraction method, using Gracilaria vermiculophylla as a model, followed by the characterization of the antimicrobial activity of different solvent extracts of Gracilaria vermiculophylla, Porphyra dioica and Chondrus crispus, both from wild and from an integrated multi-trophic aquaculture system (IMTA), collected in the north of Portugal. Additionally, the fatty acid profile of the seaweed extracts was also investigated. Extraction tests included the definition of the physical state of the seaweed, temperature and type of solvents to be used during the process. Results revealed that test organisms (Gram negative and Gram positive bacteria as well as one yeast species) were more sensitive to extracts obtained with dried algae, processed continuously at higher temperatures. Results from antimicrobial activity of wild and IMTA seaweed extracts showed stronger antimicrobial activity in extracts of ethyl acetate when compared with those from methanol and diethyl ether; furthermore, among the type of microorganisms tested, there was tendency for inhibition of the Gram positive ones. In general, there appears to be a higher antimicrobial activity for the microorganisms under study in extracts obtained from aquaculture species, when compared with the wild ones. The fatty acid profile of ethyl acetate extracts revealed a predominance of saturated fatty acids (SFA), especially palmitic acid (16:0), followed by polyunsaturated fatty acids (PUFA) and monounsaturated fatty acids (MUFA). A higher content of fatty acids in aquaculture extracts of Gracilaria vermiculophylla and Porphyra dioica was also observed.
- Potential valorisation of vinification by-productsPublication . Santos, A. F.; Ferraro, V.; Cruz, I. B.; Ferreira Jorge, R.; Carvalho, A. P.; Castro, P. M. L.; Pintado, M. E.
- Biochemical profiles in the microalga Pavlova lutheri: combined effects of light intensity and temperaturePublication . Carvalho, A. P.; Monteiro, C. M.; Malcata, F. X.
- Microalgal growth and metabolic performance in biphasic bioreactorsPublication . Martins, V. H.; Carvalho, A. P.; Malcata, F. X.
- Investigação aplicada sobre biotecnologia de microalgasPublication . Meireles, L. A.; Carvalho, A. P.; Malcata, F. X.
- Potential valorisation of vinification by-productsPublication . Santos, A. F.; Ferraro, V.; Cruz, I. B.; Jorge, R. F.; Carvalho, A. P.; Castro, P. M. L.; Pintado, M. E.
- On the facile determination of nitrate in cultures of microalgaePublication . Carvalho, A. P.; Meireles, L. A.; Malcata, F. X.
- Derivatization methods for gas-chromatographic analysis of marine lipids: insight studiesPublication . Carvalho, A. P.; Malcata, F. X.