Loading...
8 results
Search Results
Now showing 1 - 8 of 8
- Production of a carotenoid-rich product by alginate entrapment and fluid-bed drying of Dunaliella salinaPublication . Leach, Gareth; Oliveira, Gisela; Morais, RuiA new carotenoid-rich product was formed by entrapment of Dunaliella salina in calcium alginate beads of di†erent alginate concentrations, followed by drying in a Ñuid-bed dryer. The drying process yielded b-carotene recoveries of between 79 and 89% and produced a change in the 9-cis/all-trans ratio of b-carotene isomers. The carotenoid stability of the product was dependant on both the storage conditions and alginate content (range 3É3È7É3 g litre~1) of the beads. In the presence of light and oxygen total carotenoid degraded following a Ðrst order kinetic model with degradation constants between 0É016 and 0É039 days~1, with the lowest degradation occurring with the lowest alginate concentration. Product stored in the dark and Ñushed with nitrogen produced Ðrst-order degradation constants of 0É012 and 0É020 days~1 for the two higher alginate concentrations ; that with the lowest alginate content showed no noticeable degradation after 58 days storage. During storage, the 9-cis isomer was signiÐcantly more unstable showing a relative loss under all conditions, degrading almost completely when stored in the presence of light and oxygen and reaching an equilibrium ratio with the all-trans isomer when stored in the dark and Ñushed with nitrogen.
- Spray-drying of Dunaliella salina to produce a β -carotene rich powderPublication . Leach, G.; Oliveira, G.; Morais, R.Powders of Dunaliella salina biomass were obtained by spray drying a cell concentrate under different drying regimes. A three-factor, two-level experimental design was employed to investigate the influence of inlet temperature, outlet temperature and feed solids on b-carotene recovery. The effect of microencapsulation in a polymer matrix of maltodextrin and gum arabic was also studied. All powders were stored under specific conditions to assess the stability of the native b-carotene. There was a trend indicating that lower outlet temperature yielded higher carotenoid recoveries, b-carotene recovery varying between 57% and 91%. Microencapsulated biomass yielded 100% recoveries. All non-microencapsulated powders were unstable in terms of b-carotene content in the presence of natural light and oxygen showing 90% degradation over a 7-day period. The incorporation of a microencapsulating agent had a significant increase in the storage stability. Results indicated a first-order degradation of the b-carotene in microencapsulated powders with kinetic constants of 0.06 day-1 and 0.10 day-1. HPLC analysis showed no effect of drying processes on isomer composition (9-cis-b-carotene and all-trans-b-carotene ratio). This behaviour was also observed during storage of the microencapsulated powders.
- Evaluation of different cell disruption processes on encysted cells of Haematococcus pluvialis: effects on astaxanthin recovery and implications for bio-availabilityPublication . Mendes-Pinto, M.M.; Raposo, M.F.J.; Bowen, J.; Young, A.J.; Morais, R.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.
- Biodegradation of p-chlorophenol by a microalgae consortiumPublication . Lima, Sofia A. C.; Raposo, M. F.; Castro, Paula M.L.; Morais, R. M. S. C.An aquatic communitywas recovered from a waste discharge container fed with several aromatic pollutants. After 3 months of selective enrichment with p-chlorophenol and p-nitrophenol, two microalgae species, Chlorella vulgaris and Coenochloris pyrenoidosa, were recovered from the microbial consortium. As an axenic culture, this microalgae consortium was able to remove p-chlorophenol under different photo-regimes. Cultures grown under a 24 h light regime were capable of biodegrading 50mg l 1 of p-chlorophenol within 5 days. Addition of zeolite, an adsorbing material, did not improve the p-chlorophenol removal. However, when p-chlorophenol at 150mg l 1 was fed to the culture supplemented with zeolite, the growth rate of the consortium improved, but the lag phase was longer (16 against 14 days in the absence of zeolite).
- Biodegradation of p-nitrophenol by microalgaePublication . Lima, Sofia A. C.; Castro, Paula M. L.; Morais, RuiA study was made on the use of a mixed microalgal consortium to degrade p-nitrophenol. The consortium was obtained from a microbial community in a waste container fed with the remains and by-products of medium culture containing substituted aromatic pollutants (nitrophenols, chlorophenols, fluorobenzene). After selective enrichment with p-nitrophenol (p-NP), followed by an antibiotic treatment, an axenic microalgal consortium was recovered, which was able to degrade p-nitrophenol. At a concentration of 50 mg L−1, total degradation occurred within 5 days. Two species, Chlorella vulgaris var. vulgaris f. minuscula and Coenochloris pyrenoidosa, were isolated from the microalgal consortium. The species were able to accomplish p-NP biodegradation when cultured separately, although Coenochloris pyrenoidosa was more efficient, achieving the same degradation rate as the original axenic microalgal consortium. When Coenochloris pyrenoidosa was associated with Chlorella vulgaris in a 3:1 ratio, complete removal of the nitro-aromatic compound occurred within three days. This is apparently the first report on the degradation of a nitro aromatic compound by microalgae.
- Emergent sources of prebiotics: seaweeds and microalgaePublication . Raposo, M. Filomena de J.; Morais, Alcina M. M. B.; Morais, R. M. S. C.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.
- Effect of sulphate supplementation on polysaccharide production and composition in two porphyridium cruentum strainsPublication . Sousa, A. M.; Silva, C.; Raposo, M. F. de J.; Morais, R. M.
- Evaluation of different disruption processes efficiency on encysted Haematococcus pluvialis cells for astaxanthin recovery and bioavailabilityPublication . Pinto, M. M . Mendes; Raposo, M. .F de J.; Bowen, J .; Young, A .; Morais, R.