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 study was done to prepare a nanoliposomal system incorporated with bioactive compounds extracted from microalgae (Spirulina platensis) with chitosan coating (0.5%, 1%, and 1.5% w/v) and to characterize the physicochemical and antimicrobial properties of nanoliposomes. The results show that the mean particle size was in the range of 350.1–702.5 nm with a zeta potential from −64.3 to +30.4 and a polydispersity index (PDI) of 0.22–0.55 in nanoliposomes. The encapsulation efficiency (EE%) values were significantly influenced by chitosan concentration in liposomes. The antioxidant activity of free and nanoliposomal samples was estimated using DPPH, ABTS, and FRAP assay. The antibacterial activity of free extract and nanoliposomes against common Gram-positive and Gram-negative pathogenic microorganisms (Staphylococcus aureus and Escherichia coli) was indicated by MIC and MBC. The results showed that antioxidant and antibacterial activities were significantly increased after encapsulation compared to the free algal extract. Hence, the spirulina extract encapsulated in nanoliposomes can be used as a unique delivery system for natural antioxidant and antimicrobial compounds for direct application in food.

Rosmarinus officinalis L., a member of the family Lamiaceae, is regarded as the spice with the highest antioxidant activity. In this study, the transmission electron microscopy, X-ray diffraction, and fourier transform infrared spectroscopy (FTIR) physicochemical characteristics of the nanostructure of gamma-irradiated rosemary were investigated. The particle size distribution of the gamma-irradiated rosemary prepared under irradiation at 30 kGy in a Cobalt-60 irradiator exhibited a very narrow size distribution with average size of 70 nm. The results showed that irradiated (30 kGy) and crude rosemary had similar patterns of FTIR spectra, typical of phenol compound, without any notable changes in the key bands and functional groups status. Rosemary irradiated with 50 kGy and 10 kGy showed the highest and lowest crystallinity, respectively. Rosemary crystallinity of irradiated samples was lower compared with the nonirradiated sample. Therefore, 30 kGy can be optimum for the synthesis of nanoparticles, average size of 70 nm, with low crystallinity and without any notable change in key bands compared to nonirradiated samples.