Silver nanoparticles have high potential for application in food industry, as they have the ability to inhibit a wide range of bacteria of pathogenic and spoilage origin. They can be obtained from different methods classified in physical and chemical and which are aggressive with the environment since they produce toxic waste. Nowadays, environmentally friendly methods such as green synthesis can be used, through the use of agri-food waste. The use of these wastes is a more sustainable method, because it reduces the environmental pollution, at the same time that silver nanoparticles are obtained. The aim of the present study is the green synthesis of silver nanoparticles using safflower (Carthamus tinctorius L.) aqueous extract from waste and its antibacterial activity on Staphylococcus aureus (Gram positive) and Pseudomonas fluorescens (Gram negative). The analyses by TEM showed that the assynthesized silver nanoparticles were uniform and spherical particles with an average diameter of 8.67 AE 4.7 nm and confirmed by SEM. The electron diffraction and TEM analyses showed the characteristic crystallinity of silver nanoparticles. FTIR spectroscopy confirmed that various functional groups were responsible for reducing and stabilizing during the biosynthesis process. Nanoparticles inhibited the growth of both types of bacteria from the lowest concentration evaluated (0.9 μg/mL). We conclude that silver nanoparticles synthesized in the present study have potential application as antibacterial agents in food and medicine industry.

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Nanoparticles based on chitosan modified with epigallocatechin gallate (EGCG) were synthetized by nanoprecipitation (EGCG-g-chitosan-P). Chitosan was modified by free-radical-induced grafting, which was verified by Fourier transform infrared (FTIR). Furthermore, the morphology, particle size, polydispersity index, and zeta potential of the nanoparticles were investigated. The grafting degree of EGCG, reactive oxygen species (ROS) production, antibacterial and antioxidant activities of EGCG-g-chitosan-P were evaluated and compared with those of pure EGCG and chitosan nanoparticles (Chitosan-P). FTIR results confirmed the modification of the chitosan with EGCG. The EGCG-g-chitosan-P showed spherical shapes and smoother surfaces than those of Chitosan-P. EGCG content of the grafted chitosan nanoparticles was 330 μg/g. Minimal inhibitory concentration (MIC) of EGCG-g-chitosan-P (15.6 μg/mL) was lower than Chitosan-P (31.2 μg/mL) and EGCG (500 μg/mL) against Pseudomonas fluorescens (p < 0.05). Additionally, EGCG-g-chitosan-P and Chitosan-P presented higher Staphylococcus aureus growth inhibition (100%) than EGCG at the lowest concentration tested. The nanoparticles produced an increase of ROS (p < 0.05) in both bacterial species assayed. Furthermore, EGCG-g-chitosan-P exhibited higher antioxidant activity than that of Chitosan-P (p < 0.05) in 2,2′-azino-bis (3-ethyl-benzothiazoline-6-sulfonic acid) (ABTS), 2,2-diphenyl-1-picrylhydrazyl radical (DPPH) and ferric-reducing antioxidant power assays. Based on the above results, EGCG-g-chitosan-P shows the potential for food packaging and biomedical applications.

Biosynthesis of nucleoside triphosphates is critical for bioenergetics and nucleic acid replication, and this is achieved by nucleoside diphosphate kinase (NDK). As an emerging biological model and the global importance of shrimp culture, we have addressed the study of the Pacific whiteleg shrimp (Litopenaeus vannamei) NDK. We demonstrated its activity and affinity towards deoxynucleoside diphosphates. Also, the quaternary structure obtained by gel filtration chromatography showed that shrimp NDK is a trimer. Affinity was in the micro-molar range for dADP, dGDP, dTDP and except for dCDP, which presented no detectable interaction by isothermal titration calorimetry, as described previously for Plasmodium falciparum NDK. This information is particularly important, as this enzyme could be used to test nucleotide analogs that can block white spot syndrome virus (WSSV) viral replication and to study its bioenergetics role during hypoxia and fasting.

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