This study reports on the purification and characterization of a digestive α-amylase from blue crab (Portunussegnis) viscera designated Blue Crab Amylase (BCA). The enzyme was purified to homogeneity by ultrafiltration, Sephadex G-100 gel filtration and Sepharose mono Q anion exchange chromatography, with the final purification fold of 424.02, specific activity of 1390.8 U mg⁻¹ and 27.8% recovery. BCA, showing a molecular weight of approximately 45 kDa, possesses desirable biotechnological features, such as optimal temperature of 50 °C, interesting thermal stability which is enhanced in the presence of starch, high stability towards surfactants (Tween 20, Tween 80 and Triton X-100), high specific activity, quite high storage and broad pH range stability. The enzyme displayed Km and Vmax values, of 7.5 ± 0.25 mg mL⁻¹ and 2000 ± 23 μmol min⁻¹ mg⁻¹ for potato starch, respectively. It hydrolyzed various carbohydrates and produced maltose, maltotriose and maltotetraose as the major end products of starch hydrolysis. In addition, the purified enzyme was successfully utilized for the improvement of the antioxidant potential of oat flour, which could be extended to other cereals. Interestingly, besides its suitability for application in different industrial sectors, especially food industries, the biochemical properties of BCA from the blue crab viscera provide novel features with other marine-derived enzymes and better understanding of the biodegradability of carbohydrates in marine environments, particularly in invasive alien crustaceans.

In this work, silver nanoparticles (AgNPs) were elaborated using a simple, low-cost, and reproducible method by thermal treatment at 90°C of chitooligosaccharides (COSs), produced by chitosan depolymerization using the digestives chitosanases from Portunus segnis viscera, in the presence of AgNO₃. The characterization of the obtained AgNPs, using UV–visible spectroscopy, transmission electron microscopy (TEM), dynamic light scattering (DLS), and Fourier-transform infrared (FTIR) spectroscopy analyses, showed that they are crystalline, spherical and stable for a month at 4°C. Moreover, the biological properties of the synthesized AgNPs were evaluated, proving that they exhibited interesting antioxidant and antibacterial activities. The present investigation suggested that COSs will be a good source for the preparation of AgNPs that could be useful in different industrial and biomedical applications.

Aims: This study aimed to investigate the gelation capacity of European Eel Protein Isolate (EPI) through the development of novel emulsion protein isolate-based gels (EPIGs). Furthermore, the research evaluated the extent to which fortification with bioactive European eel oil (EO) modulates the structural and functional attributes of these acid-induced gel matrices. Methods: EPIGs were synthesized via thermal treatment (90°C for 60 min) of EPI solubilized in 20% (v/v) acetic acid, followed by emulsification with EO at two distinct weight ratios: 1:2 and 1:4 (EO:EPI, w/w). The resulting gel structures were characterized using Fourier-transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), texture profile analysis (TPA), and scanning electron microscopy (SEM). Results: A 4% (w/v) EPI solution in acetic acid achieved gelation at 54°C, demonstrating superior thermal stability and significant gelling potential. FTIR analysis confirmed the successful incorporation of EO into the gel matrix, while TGA results indicated a slight increase in thermal degradation onset temperatures associated with higher EO concentrations, increasing from 375°C (EPIG1:4) to 382°C (EPIG1:2). Texture analysis revealed that incorporation of EO modestly augmented gel elasticity (from 12.93 mm to 13.19 mm), a phenomenon attributed to the stabilizing interactions between the lipid droplets and the protein network. Microstructural appraisal via SEM indicated that a higher EO load (EPIG1:2) induced the formation of larger pores, whereas the EPIG1:4 formulation exhibited a more cohesive and compact architecture with reduced porosity. Keywords: European Eel; Emulsion Protein Isolate-based Gel; FTIR; Thermogravimetric; SEM.