This study investigated peptide fractions from fish skin collagen for antibacterial activity against Escherichia coli and Salmonella strains. The collagen was hydrolyzed with six commercial proteases, including trypsin, Alcalase, Neutrase, Flavourzyme, pepsin and papain. Hydrolyzed samples obtained with trypsin and Alcalase had the largest number of small peptides (molecular weight <10 kDa), while the hydrolysate produced with papain showed the lowest degree of hydrolysis and highest number of large peptides. Four hydrolysates were found to inhibit the growth of the Gram-negative bacteria, with papain hydrolysate showing the best activity against E. coli, and Neutrase and papain hydrolysates showing the best activity against S. abony; hydrolysates produced with trypsin and pepsin did not show detectable antibacterial activity. After acetone fractionation of the latter hydrolysates, the peptide fractions demonstrated enhanced dose-dependent inhibition of the growth (colony-forming units) of four Salmonella strains, including S. abony (NCTC 6017), S. typhimurium (ATCC 13311), S. typhimurium (ATCC 14028) and S. chol (ATCC 10708). Shotgun peptidomics analysis of the acetone fractions of Neutrase and papain hydrolysates resulted in the identification of 71 and 103 peptides, respectively, with chain lengths of 6–22 and 6–24, respectively. This work provided an array of peptide sequences from fish skin collagen for pharmacophore identification, structure–activity relationship studies, and further investigation as food-based antibacterial agents against pathogenic microorganisms.

This work aimed to determine the physicochemical and biochemical properties of trypsin from beluga Huso huso and sevruga Acipenser stellatus, two highly valuable sturgeon species. According to the results obtained from the methods of casein-zymogram and inhibitory activity staining, the molecular weight of trypsin for sevruga and beluga was 27.5 and 29.5 kDa, respectively. Optimum pH and temperature values for both trypsins were recorded at 8.5 and 55 °C by BAPNA (a specific substrate), respectively. The stability of both trypsins was well-preserved at pH values from 6.0 to 11.0 and temperatures up to 50 °C. TLCK and SBTI, two specific trypsin inhibitors, showed a significant inhibitory effect on the enzymatic activity of both trypsins (p < 0.05). The enzyme activity was significantly increased in the presence of Ca⁺² and surfactants and decreased by oxidizing agents, Cu⁺², Zn⁺², and Co⁺² (p < 0.05). However, univalent ions Na⁺ and K⁺ did not show any significant effect on the activity of both trypsins (p > 0.05). The results of our study show that the properties of trypsin from beluga and sevruga are in agreement with data reported in bony fish and can contribute to the clear understanding of trypsin activity in these primitive species.

In the present study, the antioxidant properties of different molecular weight fractions and different concentrations of protein hydrolysate from Common carp (Cyprinus carpio) head were investigated. Fish heads were hydrolyzed by Alcalase enzyme (1% v/w) at 55˚C and pH 8 during 180 min. The supernatant was fractionated to three different molecular ...

Freezing and thawing are critical techniques for preserving seafood quality and extending shelf life. This study evaluated the effects of ultrasound‐assisted (UT), water immersion (WT), and microwave (MT) thawing on physicochemical, textural, and structural quality attributes of common carp ( Cyprinus carpio ) fillets and their myofibrillar protein properties. Results demonstrated that ultrasound thawing (UT) most effectively maintained pH and minimized protein aggregation, reducing myofibrillar protein particle size by approximately 49%, significantly lowering turbidity, and decreasing cooking loss by about 10% compared with water immersion thawing (WT). In contrast, water immersion thawing resulted in the greatest moisture loss, whereas ultrasound and microwave thawing better preserved water‐holding capacity. Scanning electron microscopy revealed that WT and MT caused minor muscle damage, whereas UT better preserved protein integrity, showing significantly reduced aggregation and higher zeta potential compared with MT ( p < 0.05). SDS‐PAGE confirmed that no treatments altered the primary protein structure. Based on overall quality retention, ultrasound thawing is recommended as the optimal thawing method for common carp fillets.