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Fungal chitosan was extracted from Aspergillus niger mycelia. The produced chitosan was characterized with deacetylation degree of 89.2%, a molecular weight of 2.4 × 10 4 Da, and 96.0% solubility in 1% acetic acid solution. The antibacterial activity of fungal chitosan was evaluated against two foodborne pathogens, that is, Salmonella typhimurium and Staphylococcus aureus, using the established antibacterial assays, for example, zone of growth inhibition and agar plat count tests, and using 2,3,5,-triphenyltetrazolium chloride (TTC) as chromogenic marker for qualitative and quantitative determining of antibacterial potentiality. The TTC (0.5% w/v) was added, at concentration of 10%, to cultured broth, containing chitosan with different concentrations then the formed formazan was separated. The formation of red formazan could be considered as a qualitative indication for antibacterial activity, whereas the measurement of color intensity for the resuspended red formazan, using spectrophotometer at 480 nm, provided a quantitative evidence for the strength of the used antibacterial agent. Regarding the rapidity, technical simplicity, and cost-effectiveness, TTC assay could be recommended as an efficient alternative method for qualitative and quantitative determination of chitosan antibacterial activity and could be suggested for general evaluation of antibacterial agents.

Bioactive nanocomposites were constructed, containing chitosan (Cht), extracted from shrimps’ wastes, and transformed into nanoparticles (NPs) using ionic-gelation. Selenium NPs (Se-NPs) were phytosynthesized using cinnamon (Cinnamomum zeylanicum) bark extract (CIE), characterized and evaluated with Cht-NPs as antimicrobial composites against bacterial food-borne pathogens “Escherichia coli, Salmonella typhimurium, Staphylococcus aureus, and Listeria monocytogenes” and as potential edible coating (EC) basements. The CIE-phytosynthesized Se-NPs had well-distributed and spherical shapes with 23.2 nm mean diameter. The CIE, CIE/Se-NPs, and innovative CIE/Se/Cht-NP composites exhibited distinguished antibacterial actions toward the entire screened pathogens; CIE/Se/Cht-NP composite was significantly the most potent. The formulated ECs from CIE/Se/Cht-NP nanocomposites had matching antibacterial manner, which was strengthened with CIE/Se-NP percentage increments. Scanning micrographs indicated the attachment of CIE/Se-NPs to bacterial cells to cause their complete lysis and death after 10 h of exposure. CIE/Se/Cht-NP composites are proposed as effectual control agents toward food-borne pathogens using efficient biological carriers and eco-friendly phytosynthesis protocol.

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The antibacterial performance of sol-gel-derived inorganic-organic hybrid polymers filled with ZnO nanoparticles-chitosan against a gram-negative bacterium Escherichia coli and a gram-positive Micrococcus luteus has been investigated. Three different molecular weights (MW) of chitosan (CTS) 1.36 · 10 5 , 2.2 · 10 5 , and 3.0 · 10 5 Da with equal degree of deacetylation (DD, 85%) (coded as S 85-60, He 85-250, and He 85-500) with equal degree of deacetylation (DD, 85%) were examined. ZnO was prepared by the base hydrolysis of zinc acetate in isopropanol using lithium hydroxide (LiOH · H 2 O) to hydrolyze the precursor. Sol-gel-based inorganic-organic hybrid polymers were modified with these oxides and were applied to cellulosic cotton (100%) and cotton/polyester (65/35%) fabrics. Inorganic-organic hybrids polymers were based on 3-glycidyloxypropyltrimethoxysilane (GPTMS). Bacteriological tests were performed in nutrient agar media on solid agar plates and in liquid broth systems using ZnO nanoparticles with average particle size of (40 nm). Our study showed the enhanced antibacterial activity of ZnO nanoparticles chitosan (different MW) of against a gram-negative bacterium Escherichia coli DSMZ 498 and a gram-positive Micrococcus luteus ATCC 9341 in repeated experiments. The antibacterial activity of textile treated with ZnO nanoparticles chitosan increases with decreasing the molecular weight of chitosan.

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Here we report the phycosynthesis of silver nanoparticles (Ag-NPs), using Codium capitatum extract, and the synthesis of fungal chitosan nanoparticles (FC-NPs), using extracted chitosan from Aspergillus niger mycelia. Then nanoconjugates from FC/Ag-NPs were produced and evaluated. The synthesized NPs had mean particles' size diameters of 37.2, 68.4 and 79.6 nm for Ag-NPs, FC-NPs and FC/Ag-NPs, respectively. The FTIR (Fourier-transform infrared spectroscopy) analysis of synthesized NPs indicated their cross-linkage and interaction. The antibacterial activity of each type of NPs was assayed against drug resistant pathogens of Salmonella Typhimurium and Staphylococcus aureus. All NPs had powerful inhibitory effect and FC/Ag nanoconjugates had stronger activity than the other types. Scanning micrographs of FC/Ag-NPs treated S. Typhimurium elucidated vigorous alterations in cell surfaces and lethal damage to bacterial structure after 8 h of treatment. The nanoconjugates form FC-NPs and Ag-NPs had minute particle size with increasing bioactivity as antimicrobial agents to control drug resistant bacterial pathogens, which recommends their further exploration for topical applications in biomedical sectors.

Shrimps are highly valuable and perishable foodstuff that could be rapidly spoiled. Chitosan (Cht) was extracted and transformed into nanoparticles (NPs) via ionic gelation and fortified with cloves (Syzygium aromaticum) buds extract (CLE) for usage as antimicrobial composites against food-borne bacterial pathogens (Escherichia coli, Salmonella typhimurium, and Staphylococcus aureus) and as edible coating (EC) for shrimp (Fenneropenaeus indicus) biopreservation throughout refrigerated storage. The synthesized CLE/Cht-NPs were electrostatically cross-linked and appeared with spherical shapes and homogenized distribution, with 159.4 nm mean size diameter and positive charge of 17.4 mV. The entire agents (Cht-NPs, CLE, and CLE/Cht-NPs) exhibited remarkable antibacterial activities toward all food-borne pathogens; CLE/Cht-NPs were significantly the most forceful. The scanning micrographs of treated S. typhimurium with CLE/Cht-NPs displayed NPs ability to attach and destroy bacterial cells. The ECs-treated shrimps exhibited sharp decrease in microbial groups load (aerobic microorganisms, E. coli, Enterobacteriaceae, and staphylococci) during refrigerated storage (4 ± 1°C) for 10 days. Additionally, the sensorial attributes (appearance, odor, color, and texture) of EC-treated samples preserved their elevated qualities for storage duration. The most effective EC blend contained 1.5% from Cht/NPs and 1.0% from CLE. The CLE/Cht-NPs could be impressively recommended as effectual natural composites for shrimps’ biopreservation during cold storage.