Maria Filomena de Jesus Raposo

Evaluation of different cell disruption processes on encysted cells of Haematococcus pluvialis: effects on astaxanthin recovery and implications for bio-availability

Although Haematococcus pluvialis is one of the most importantnatural sources of the carotenoid astaxanthin as a pigmentor for theaquaculture industry, the thick sporopollenin cell wall in the cysts hindersastaxanthin extraction and its subsequent bio-availability to fish. A rangeof physical and chemical processes were tested to promote the disruptionof the encysted cells. The efficacy of these processes was evaluated interms of astaxanthin recovery, which was assessed by determining theextent of leaching of astaxanthin into an organic solvent. The processestested were: autoclave 30 min, 121 °C, 1 atm; HCl 0.1 M, 15min and 30 min; NaOH 0.1 M, 15 min and 30 min; enzymatictreatment with a mixture of 0.1% protease K and 0.5% driselase in aphosphate buffer, pH 5.8, 30 °C, for one hour; spray drying, inlet180 °C, outlet 115 °C; and mechanical disruption, with acell homogeniser developed for this purpose. The mechanical(homogenisation) and autoclave treatments were the most effective in termsof extraction and availability.

Marine Polysaccharides from Algae with Potential Biomedical Applications

There is a current tendency towards bioactive natural products with applications in various industries, such as pharmaceutical, biomedical, cosmetics and food. This has put some emphasis in research on marine organisms, including macroalgae and microalgae, among others. Polysaccharides with marine origin constitute one type of these biochemical compounds that have already proved to have several important properties, such as anticoagulant and/or antithrombotic, immunomodulatory ability, antitumor and cancer preventive, antilipidaemic and hypoglycaemic, antibiotics and anti-inflammatory and antioxidant, making them promising bioactive products and biomaterials with a wide range of applications. Their properties are mainly due to their structure and physicochemical characteristics, which depend on the organism they are produced by. In the biomedical field, the polysaccharides from algae can be used in controlled drug delivery, wound management, and regenerative medicine. This review will focus on the biomedical applications of marine polysaccharides from algae.

Health applications of bioactive compounds from marine microalgae

Marine microalgae and cyanobacteria are very rich in several chemical compounds and, therefore, they may be used in several biological applications related with health benefits, among others. This review brings the research up-to-date on the bioactive compounds produced by marine unicellular algae, directly or indirectly related to human health. It covers and goes through the most studied applications of substances such as PUFA, sterols, proteins and enzymes, vitamins and pigments, in areas so diverse as human and animal nutrition, therapeutics, and aquaculture. The great potential of marine microalgae and the biocoumpounds they produce are discussed in this review.

Emergent Sources of Prebiotics: Seaweeds and Microalgae

In recent years, scientists have become aware that human microbiota, in general, and gut microbiota, in particular, play a major role in human health and diseases, such as obesity and diabetes, among others. A large number of evidence has come to light regarding the beneficial effects, either for the host or the gut microbiota, of some foods and food ingredients or biochemical compounds. Among these, the most promising seem to be polysaccharides (PS) or their derivatives, and they include the dietary fibers. Some of these PS can be found in seaweeds and microalgae, some being soluble fibers, such as alginates, fucoidans, carrageenans and exopolysaccharides, that are not fermented, at least not completely, by colonic microbiota. This review gives an overview of the importance of the dietary fibers, as well as the benefits of prebiotics, to human health. The potential of the PS from marine macro- and microalgae to act as prebiotics is discussed, and the different techniques to obtain oligosaccharides from PS are presented. The mechanisms of the benefits of fiber, in general, and the types and benefits of algal fibers in human health are highlighted. The findings of some recent studies that present the potential effects of prebiotics on animal models of algal biomass and their extracts, as well as oligo- and polysaccharides, are presented. In the future, the possibility of using prebiotics to modulate the microbiome, and, consequently, prevent certain human diseases is foreseen.

Influence of sulphate on the composition and antibacterial and antiviral properties of the exopolysaccharide from Porphyridium cruentum

AIMS The influence of two culture media and three different concentrations of sulphate in the medium on the growth of two strains of Porphyridium cruentum and on the production, composition and viscoelastic characteristics, and antimicrobial properties of the sulphated exopolysaccharide (EPS) were studied. MAIN METHODS A Bohlin C50 rheometer was used to evaluate the viscosity and elasticity of the EPS solutions. HSV virus, types 1 and 2, Vaccinia virus and Vesicular stomatitis virus were used along with two Gram-negative (Escherichia coli and Salmonella enteritidis) and one Gram-positive (Staphylococcus aureus) bacteria, for testing the antimicrobial activity of EPS. KEY-FINDINGS The growth of microalgae was higher in NTIP medium and the production of EPS was enhanced by sulphate 21mM. The protein content of the EPS was enhanced by the addition of sulphate 52mM and 104mM; this concentration also induced an increase in sulphate content of the EPS. However, neither the contents of EPS in carbohydrates and uronic acids were affected by the culture medium supplementation in sulphate. In general, the EPS from the Spanish strain presented a higher antiviral activity than the EPS from the Israeli strain. All EPS extracts revealed a strong activity against V. stomatitis virus, higher than the activity of all chemical compounds tested. The EPS from the Israeli strain also presented antibacterial activity against S. enteritidis. SIGNIFICANCE Enrichment of the culture medium with sulphate improved protein and sulphate content of EPS. EPS extracts presented a relevant activity against V. stomatitis virus and S. enteritidis bacterium.

Carotenoids from Marine Microalgae: A Valuable Natural Source for the Prevention of Chronic Diseases

Epidemiological studies have shown a relation between antioxidants and the prevention of several chronic diseases. Microalgae are a potential novel source of bioactive molecules, including a wide range of different carotenoids that can be used as nutraceuticals, food supplements and novel food products. The objective of this review is (i) to update the research that has been carried out on the most known carotenoids produced by marine microalgae, including reporting on their high potentialities to produce other less known important compounds; (ii) to compile the work that has been done in order to establish some relationship between carotenoids and oxidative protection and treatment; (iii) to summarize the association of oxidative stress and the various reactive species including free radicals with several human diseases; and (iv) to provide evidence of the potential of carotenoids from marine microalgae to be used as therapeutics to treat or prevent these oxidative stress-related diseases.

Microalgae for the prevention of cardiovascular disease and stroke.

This review focuses on and discusses the primary phytochemicals present in microalgal biomass - carotenoids, phenolic compounds, antioxidant vitamins, sterols, and polyunsaturated fatty acids - and also on the exopolysaccharides, which are produced by some types of microalgae and may play a significant role in the prevention of cardiovascular diseases (CVD) and strokes. We have listed several preclinical trials and clinical studies supporting the health benefits that most of these compounds may provide. Microalgae are very easy to grow and are not vulnerable to contaminants when grown under controlled conditions. Proper handling and growth conditions may improve the production of phytochemicals. Therefore, they may represent an excellent source of nutraceuticals and food supplements once their safety as a food supplement has been confirmed.

Influence of the Growth Regulators Kinetin and 2,4-D on the Growth of Two Chlorophyte Microalgae, Haematococcus pluvialis and Dunaliella salina

Abstract : Haematococcus pluvialis Flotow and Dunaliella salina Teodoresco are commercially important because of their ability to accumulate very high carotenoid contents. However, their use is hindered by their slow growth rates. This paper reports a study on the effects of two growth regulators, 2,4-D (2,4-dichlorophenoxyacetic acid) and kin (kinetin), in concentrations of 0, 0.5, 1.0 and 2.0 mg l -1 each in a factorial design (2 4 combinations), as a possible means of enhancing the growth rates. After 12-13 days of treatment with plant hormones, D. salina showed a significant increase in growth with all the hormone concentrations and combinations used and under 15% salinity (NaCl, w/v), (except for 0.5 mg l -1 2,4-D and no kin), with up to 410% more cells than the control; under 10% salinity (NaCl, w/v), the increase in growth was significant with 0.5 mg l -1 2,4-D and no kin (180% more cells than the control), and also with 1.0 mg l -1 2,4-D and no kin (126% more cells than the control) and 2.0 mg l -1 2,4-D and 0.5 mg l -1 kin (134% more cells than the control) in the culture medium. Cultures of H. pluvialis were significantly influenced under 1.0 mg l -1 2,4-D (with 320% more cells than the control), but also showed a significant increase in the growth rate when the ratio auxin to cytokinin was 1 (equal concentrations of 1.0 mg l -1 of both growth regulators) with more than 290% cells than the control, and with 0.5 mg l -1 2,4-D and 2.0 mg l -1 kin (200% more cells than the control) in the culture medium.

Chemical dips and edible coatings to retard softening and browning of fresh-cut banana

The effects of chemical dips and edible coatings on firmness and colour of fresh-cut banana (cv. Cavendish) from Madeira Island were investigated. Two calcium salts, calcium chloride and calcium lactate, were first investigated for the effects on firmness during four days of storage at 5°C. Firmness and colour were evaluated after a three-minute chemical dipping or chemical dipping followed by coating and during five days of storage at 5°C. The coatings tested consisted of pectin, alginate, carboxymethylcelullose, carrageenan or chitosan solution. Dip with 1% (w/v) calcium chloride, 0.50% (w/v) ascorbic acid and 0.75% (w/v) cysteine was the most efficient treatment in retarding softening and browning of banana slices. This dip also inhibited yeast growth. According to sensory analysis, the edible shelf life of banana slices dipped in such solution was the longest: five days at 5°C. Carrageenan solution was the significantly (p < 0.05) best coating among the ones studied, in preserving firmness and colour of fresh-cut banana during five days at 5°C.

Polyphenol oxidase activity and colour changes of peeled potato (cv. Monalisa) in vacuum

Minimal processing of vegetables has some undesirable physiological consequences. The shelf life of peeled raw potatoes is limited by the onset of enzymatic browning at the cut surfaces. It is generally accepted that polyphenol oxidase (PPO) is the enzyme mainly responsible for this type of browning. This work aimed to study the effect of vacuum storage at 4°C on the colour, which is the main parameter limiting the shelf life of potato (cv. Monalisa). PPO activity was evaluated as well with the aim to investigate the relation with colour changes.