Abstract
Despite decades of research on marine algae, there are still significant gaps in basic knowledge about chemical composition of these organisms, especially in tropical environments. In this study, the amino acid composition and contents of total nitrogen, phosphorus, lipid, carbohydrate and protein were determined in Asparagopsis taxiformis, Centroceras clavulatum, Chaetomorpha aerea, Sargassum filipendula and Spyridia hypnoides. The seaweeds showed low lipid contents (lower than 5.5% d.w. in all species) and were rich in carbohydrates (more than 16% d.w. in all seaweeds). The percentage of nitrogen, phosphorus and protein varied widely among species, which red algae showed the highest con-centrations. The amino acid composition was similar among the seaweeds, which glutamic acid, aspartic acid and leu-cine as the most abundant. All species are poor in histidine. An average of 24.2% of the total nitrogen is non-proteinaceous. From data of total amino acid and total nitrogen, specific nitrogen-to-protein conversion factors were calculated for each species. The nitrogen-to-protein conversion factors calculated ranged from 4.51 to 5.21, with an overall average of 4.86. These findings show that the traditional conversion factor of 6.25 should be avoided for seaweeds, since it overestimates the actual protein content.
Highlights
Utilization of algae has increased considerably over the past years as a consequence of growth of research in various fields [1]
The nitrogen-to-protein conversion factors calculated ranged from 4.51 to 5.21, with an overall average of 4.86. These findings show that the traditional conversion factor of 6.25 should be avoided for seaweeds, since it overestimates the actual protein content
The hydrosoluble protein contents ranged from 8.7% (S. filipendula, brown alga) to 16.1% (C. aerea, green alga) of the dry weight with intermediate and similar concentrations (p > 0.05) in red algae (Table 1)
Summary
Utilization of algae has increased considerably over the past years as a consequence of growth of research in various fields [1]. Because seaweed species are rich in beneficial nutrients, in countries such as China, Japan and Korea, they have been commonly utilized in human nutrition for centuries [2]. They have been found to be good sources of vitamins, carbohydrates, minerals and proteins [3], but show wide variations among species. Seaweeds have been increasingly viewed as potential sources of bioactive compounds with immense pharmaceutical, biomedical and nutraceutical importance [4] They have been used in agricultural and industrial research due to their high content of carbohydrates, proteins, vitamins, and minerals [5], but show wide variations among species. Data on the bioavailability of these components are limited
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