Chitin was extracted from Polybius henslowii, a swimming crab, captured in large quantities throughout the Portuguese coast by purse seine vessels as bycatch. After standard chitin extraction procedures, water-soluble chitosan products were obtained via two different methods: (1) N-acetylation with the addition of acetic anhydride and (2) a reaction with hydrogen peroxide. The chemical structure and molecular weight of chitosan derivatives, water-soluble chitosan (WSC) and chitooligosaccharides (COS), were confirmed by Fourier Transform Infrared Spectroscopy (FT-IR) and gel permeation chromatography (GPC). Antioxidant and metal chelation activities were evaluated, and the growth inhibition capacity was tested on four phytopatogens. The chitooligosaccharides from pereopods (pCOS) and shell body parts (sCOS) inhibited all fungal species tested, particularly Cryphonectria parasitica with 84.7% and 85.5%, respectively. Both radical scavenging and antifungal activities proved to be dose-dependent. Chitooligosaccharides with a low molecular weight (2.7, 7.4, and 10.4 Kg·mol⁻¹) showed the highest activity among all properties tested. These results suggested that chitosan derivatives from P. henslowii raw material could potentially be used against phytopathogens or as ingredient in cosmetics and other products related to oxidative stress.

Over the last years, algae have been increasingly used in Human food due their rich chemical and nutritional composition, particularly the high supply of essential nutrients to the human body such as protein and dietary fiber. Dietary fiber can be divided into two different types: soluble and insoluble. The characteristics of soluble dietary fiber are related to some physical and chemical properties such as rehydration ratio and water holding capacity and are important in assigning the functional and organoleptic properties and in preventing some human pathologies such as cardiovascular disease and obesity. The present study aimed to investigate the influence of different drying conditions on the rehydration ratio and water holding capacity of three green algae, Codium vermilara, Codium tomentosum and Ulva lactuca. The methods used for the determination of water retention capacity and rehydration ratio were similar to those used in previous studies (Susuki, T. et al., 1996). The algae were processed in a tray dryer and the drying conditions were: Temperature: 30ºC and 40ºC; Relative Humidity: 28%-47%; air velocity 1,9 m/s. In this work, it was concluded that higher drying temperature conditions originate lower rehydration ratio and consequent lower water holding capacity possibly due to a higher physical damage in the algae tissues. It was also observed that both Codium species have higher values for these two parameters than Ulva lactuca, under the same rehydration conditions.

Marine macroalgae are important sources of sulfated polysaccharides with different structure according to each species of algae. These compounds from the seaweeds of the division Rhodophyta are mainly galactans consisting entirely of galactose or modified galactose units. Galactans, like agar and carrageenan have important biotechnological and commercial applications in several industries. The red seaweed Asparagopsis armata (Harvey), originally from the Pacific Ocean, is well established in Peniche beaches (west of Portugal) and other European locations and was classified as an invasive species. These red algae show complex hybrid galactans in their composition. The water–soluble polysaccharides were extracted from the gametophyte form of the seaweed, collected in March 2013 from Peniche coast, using a hot water extraction procedure. The yield (%) of the extraction and the galactose ratio content (mmol glucose %) were calculated. The polysaccharides were characterized by Infrared spectroscopy. The yield of polysaccharides was 16% and the calculated galactose ratio was 0.30 mmol glucose %. No significant statistical differences between the extraction procedures and the yield result were found. The FTIR spectra presented different bands, such as a band at 843.59 cm-1, characteristic of C4-O-S in galactose unit and a band at 764.68 cm-1 of C2-O-S (3.6-anidrogalactose). The complex hybrid galactans extracted from A. armata are easily obtained from simple extraction procedures. Nevertheless, a better molecular characterization is required, in order to determine the potential of these seaweeds as a galactan source, and compare these polysaccharides with other galactans obtained from other Rodophyta species.