Physiological and physico-chemical characterization of dietary fibre from the green seaweed Ulva fasciata Delile / Caracterização fisiológica e físico-química da fibra alimentar da macroalga marinha verde Ulva fasciata Delile

This work aims to assess the potential of the green seaweed Ulva fasciata Delile as an alternative source of dietary fibre (DF). Total DF content was determined, some of its physico-chemical properties described and the physiological effects of U. fasciata meal on rats fed a hypercholesterolemic diet were investigated. U. fasciata may be considered a potential alternative source of DF with a total content of about 400 g.kg-1 (dry basis) and interesting physico-chemical properties: water retention capacity of 8.74 g/water.g-1 dry sample (seaweed meal) and 0.90 (seaweed carbohydrate extract), lipid adsorption capacity of 4.52 g/oil.g-1 dry sample (seaweed meal) and 5.70 (seaweed carbohydrate extract), intrinsic viscosity of 2.4 dl.g-1 (seaweed carbohydrate extract) and cation exchange capacity of 3.51 Eq.kg-1 (seaweed carbohydrate extract). The diet containing seaweed meal was able to keep rats' total cholesterol (TC) down without causing any undesirable increase in LDL-C fraction. No evidence of toxic and/or antinutritional components in the seaweed meal was detected. Rats showed a fecal volume much greater (13 g) than that fed on cellulose diet ( 7 g) (p < 0.05). These properties confer on the seaweed the potential to be used in food technology for the acquisition of low-calorie food and might be important in body weight control, reduction of blood TC and LDL-C as well as in prevention of gastrointestinal diseases.

Este trabalho objetivou avaliar o potencial da alga marinha verde Ulva fasciata Delile como fonte alternativa de fibra alimentar. Foram realizadas a determinação do teor de fibra alimentar total e a descrição de algumas propriedades físico-químicas, e os efeitos fisiológicos da farinha da alga seca sobre ratos alimentados com dieta hipercolesterolemizante foram investigados. Esta alga pode ser considerada uma fonte alternativa potencial de fibra com cerca de 400 g.kg-1 (base seca) e propriedades físico-químicas interessantes: uma capacidade de retenção de água de 8,74 g/água.g-1 de amostra seca (farinha de alga) e 0,90 (extrato de carboidratos), uma capacidade de adsorção de lipídeos de 4,52 g/óleo.g-1 de amostra seca (farinha de alga) e 5,70 (extrato de carboidratos), uma viscosidade intrínseca de 2,4 dl.g-1 (extrato de carboidrato da alga) e capacidade de troca iônica de 3,51 Eq.kg-1 (extrato de carboidrato). A dieta contendo farinha de alga foi capaz de manter baixos os níveis de colesterol total de ratos sem causar aumento indesejável na fração LDL-C. Nenhuma evidência de componentes tóxicos e/ou antinutricionais na farinha de alga foi encontrada. Os ratos mostraram um volume fecal maior (13 g) do que aqueles alimentados com dieta contendo celulose como fonte de fibra (7 g) (p < 0,05). Essas propriedades conferem a alga o potencial de ser utilizada na tecnologia de alimentos para a aquisição de alimentos de baixas calorias, podendo ser importante para o controle do peso corporal, redução do colesterol sanguíneo total e da fração LDL-C, como também na prevenção de doenças gastrintestinais.

Rapid attachment of spores of the fouling alga Ulva fasciata on biofilms.

Attachment of spores of Ulva fasciata to natural biofilms was examined to probe the basis for specificity in settlement. Within 30 min from initial exposure in laboratory assays, spores attached to 1-, 3-, 6- or 9-day biofilms formed on acid-cleaned glass slides. The greatest number of spores attached to biofilms aged for 6-day (573.3 +/- 45 spores mm2, p<0.025). The Morisita Index (MI) was used to investigate relationships between the spatial pattern of spores on natural biofilms, and was found to be random for 1-, 3- and 6-day biofilms (MI = 0.93, 0.98 and 0.95, respectively), but non-random on 9-day biofilms (0.82). In addition to the attachment of spores to natural biofilms, experimentally manipulated biofilms that provided potentially specific receptor sites were studied. Epifluorescence microscopy of 1-day biofilms confirmed that experimental sugar was incorporated into natural biofilms. The Jacalin galactose specific probe showed a homogeneous pattem of galactose incorporation on biofilms, whereas Concanavalin Aprobe (mannose) showed a discrete pattem for this sugar. Similarly, the addition offetuin to a biofilm was detected as a heterogeneous pattern. Rapid spore attachment of U. fasciata found on natural biotilms was induced by fetuin (1-day: 1482 +/- 46.6 spores mm2); specific molecules similar to fetuin may play a role in triggering settlement Specific sugars and their analogs are important surface receptors and play an integral role in attachment of Ulva fasciata spores to aged biofilms. Biofilm age and the role of specific sugars on attachment are discussed.