Recent findings in molecular reactions of E. coli as exposed to alkylated, nano- and ordinary chitosans.

The antibacterial effects of chitosan have been widely studied, but the underlying molecular mechanisms are not fully understood. We investigated the molecular responses of Escherichia coli MG1655 cell, a model gram-negative bacterium, upon exposure to chitosan (Cs), alkylated Cs (AlkCs), and chitosan nanoparticles (CsNPs). Nine target genes involved in relevant signaling pathways (ompF, ompC, ompA, mrcA, mrcB, mgtA, glnA, kdpA, lptA) were selected for analysis. A significant reduction in the expression of mrcA, mgtA, glnA, and lptA genes was observed in the cells treated with Cs. Those treated with Cs, AlkCs, and CsNPs revealed an increase in ompF gene expression, but the expression level was lower in the cells treated with AlkCs and CsNPs compared to Cs. This increase in porin expression suggests compromised membrane integrity and disrupted nutrient transport. In addition, the changes in the expression of mgtA, kdpA, and glnA are related to different effects on membrane permeability. The higher expression in the genes mrcA and mrcB is associated with morphological changes of cells treated with AlkCs and CsNPs. These findings contribute to our understanding of the molecular mechanisms underlying chitosan-induced stress responses and provide insights for the development of safer antimicrobial compounds in the future.

Physicochemical and functional characterization of gelatin edible film incorporated with fucoidan isolated from Sargassum tenerrimum.

Biodegradable films were created with fish gelatin and fucoidan extracted from Sargassum tenerrimum using 30% glycerol as a plasticizer. The gelatin films were incorporated with fucoidan (2.5%, 5%, 7.5%, and 10%), respectively. Results presented that the average thickness of films ranged from 0.12 to 0.147 mm. Tensile strength (TS) was decreased from 29.27 to 3.46 MPa by adding the fucoidan except for the gelatin/fucoidan 10% (5.35 MPa) sample. The results showed that the physical characteristics (the contact angle (Ɵ), water solubility, opacity, and moisture content) of the films significantly changed depending on different fucoidan concentrations. FTIR and SEM analysis confirmed the interaction of fucoidan with gelatin in the composite film. Furthermore, adding 10% fucoidan showed high DPPH radical scavenging activity (65%) than other treatments. Therefore, incorporation of fucoidan extracted from brown algae (Sargassum tenerrimum) with fish gelatin films improved thermal stability, anti-oxidative, and antibacterial characteristics in addition to enhanced mechanical and protective properties, to be used as a bioactive edible film in the food packaging industry.

Development of stability, antioxidant, and antimicrobial properties of biopolymeric chitosan- modified starch nanocapsules containing essential oil.

Lemon essential oil (LEOs) is used as a bioactive compound with unique health properties as a medicine or dietary supplement. Nevertheless, essential oils are chemical compounds sensitive to light, oxidation, and thermal processes. Therefore, encapsulation technique can be a good way to protect them from degradation and evaporation. In current study, biopolymeric nanocapsules containing lemon essential oils (LEOs) were prepared by the emulsion method. The nanocapsules were characterized by their particle size and Encapsulation efficiency (%) ranged from 339.3 to 553.3 nm and 68.09% to 85.43%, respectively. Long-term storage (30 days) under different temperatures (4°C, 25°C, and 40°C) conditions showed that nanocapsules stored at 4°C were more stable than samples stored at higher temperatures. DPPH and ABTS free radical scavenging activity were measured to evaluate the values of antioxidant activity of LEOs and nanocapsules. The free LEO and nanocapsules were investigated for its antibacterial activity against common Gram-positive and Gram-negative pathogenic microorganisms (Staphylococcus aureus and Escherichia coli) using disk diffusion followed by the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC). Our results indicated that the encapsulated LEOs had a significant antioxidant and antibacterial activities, as compared to the free LEO. The LEOs nanocapsules in CS and Hicap can be suggested as an important natural alternative with suitable stability, antioxidant, and antibacterial properties to overcome the challenges associated with the direct application of these bioactive compounds in food.

Development of antimicrobial gelatin-ulvan-beeswax composite films: Optimization of formulation using mixture design methodology.

A new generation of antimicrobial film was developed by incorporation of ulvan extracted from Ulva intestinalis into gelatin from common carp scale and its water sensitivity was reduced with addition of beeswax. Optimum composition of gelatin (0-100%w/w), ulvan (0-100%w/w) and beeswax (0-10%w/w) for achieving composite films with minimum water solubility (S) and water vapor permeability (WVP) and maximum tensile strength (TS), elongation at break point (EAB) and antibacterial effect on E. coli (EC) were investigated using mixture design methodology. Both pure gelatin and ulvan films and their composites had relatively good mechanical and optical properties. Addition of ulvan to gelatin produced composite films with good antibacterial properties but water resistance of all the films was weak. Addition of beeswax up to ∼5 % improved the water resistance and mechanical properties of the films without jeopardizing their antibacterial properties. The final optimum formulation with a desirability of 0.709 was achieved as 52.18 % of gelatin, 40.83 % of ulvan and 6.97 % of beeswax resulting in a minimum possible S (40 %) and WVP (1.86 10-10 g/ms Pa) and maximum possible TS (6.23 MPa) and EAB (89 %) with good EC (7.66 mm). Finally, good mechanical, thermal and microstructural properties of the optimum composite film was confirmed. Altogether, a combination of ulvan and beeswax can be a promising solution for development of gelatin films with both antimicrobial properties and lower water sensitivity.

Anti-Salmonella Activity and Peptidomic Profiling of Peptide Fractions Produced from Sturgeon Fish Skin Collagen (Huso huso) Using Commercial Enzymes.

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.

Shelf-life and quality of chicken nuggets fortified with encapsulated fish oil and garlic essential oil during refrigerated storage.

Fish oil (FO) is a rich source of long-chain omega-3 polyunsaturated fatty acids (ω-3 LCPUFA) which are important for human health. This research investigated the fortification of chicken nuggets with encapsulated FO-Garlic essential oil (GEO) as a possible way for delivery of ω-3 LCPUFA. Five different chicken nugget samples were prepared according to different treatments: Control sample (without fish oil and encapsulated FO-GEO), bulk fish oil samples (0.4% and 0.8%, w/w), and encapsulated FO-GEO samples (4% and 8%, w/w). The quality of the chicken nugget samples were monitored during a 20-day refrigerated storage. Results showed that the addition of encapsulated FO-GEO could significantly delay lipid oxidation and microbiological spoilage of the samples during refrigerated storage. This is reflected by the pH, PV, TBARS and TVBN data (P < 0.05). Samples fortified with encapsulated FO-GEO also showed significantly higher sensory quality and overall acceptability (P < 0.05). The use of 8% encapsulated FO-GEO gave the best antioxidative and antimicrobial properties during storage. However, the best sensory scores were observed in the 4% encapsulated FO-GEO up to 20 days of storage. This study demonstrated that the encapsulated FO-GEO could be used for fortifying and extending shelf-life of food products.

Biochemical and structural characterization of sturgeon fish skin collagen (Huso huso).

The potential use of sturgeon fish skin waste (Huso huso), an Iranian major sturgeon species, as a rich source for collagen extraction was evaluated. Yields of ASC and PSC obtained by acidic and enzymatic extractions were 9.98% and 9.08% (based on wet weight), respectively. SDS-PAGE profiles of both collagens led to classification of the proteins as type I with two different α chains (α1 and α2 ). Scanning electron microscopy (SEM) of the collagen sponges indicated dense sheet-like film linked by random-coiled filaments. Glycine was the most predominant amino acid, and the imino acids contents were 21.14% and 21.58% for ASC and PSC, respectively. Fourier-transform infrared spectra (FTIR) confirmed that pepsin digestion did not disrupt PSC triple helical structure. Denaturation and melting temperatures of ASC and PSC were 29.34°C, 92.03°C, and 29.89°C, 88.93°C, respectively. Thus, the sturgeon fish skin waste could serve as an alternative collagenous source for biomedical materials, food, and pharmaceutical applications. PRACTICAL APPLICATIONS: Beluga (Huso huso) is one of the most important sturgeon fish on the Caspian Sea and aquaculture industries. With the exception of the meat and caviar, wastes generated after their processing are usually discarded. Skin and cartilage of sturgeon fish are the by-products of the processing, and they are often discarded as waste or used for low-value purposes, although they are a good source for production of collagen-based biomaterials. Collagen type I is the most abundant collagen in the skin and this work reports the sturgeon fish skin as an important collagen resource with potential for use in the food, biomedical, and cosmetic industries.

Characterization of Gamma-Irradiated Rosmarinus officinalis L. (Rosemary).

OBJECTIVES: Rosmarinus officinalis L., a member of the family Lamiaceae, is regarded as the spice with the highest antioxidant activity. MATERIALS AND METHODS: 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. RESULTS: 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. CONCLUSION: 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.

Fractionation of Protein Hydrolysates of Fish Waste Using Membrane Ultrafiltration: Investigation of Antibacterial and Antioxidant Activities.

In this study, yellowfin tuna (Thunnus albacores) viscera were hydrolyzed with protamex to obtain hydrolysate that is separated by a membrane ultrafiltration into four molecular size fractions (< 3, 3-10, 10-30, and 30 kDa <). Antibacterial and antioxidant properties of the resulting hydrolysates and membrane fractions were characterized, and results showed that the lowermost molecular weight fraction (< 3 kDa) had significantly the highest (P < 0.05) percentage of bacteria inhibition against Gram-positive (Listeria and Staphylococcus) and Gram-negative (E. coli and Pseudomonas) pathogenic and fish spoilage-associated microorganisms and scavenging activity against DPPH and ABTS radical and ferric reducing antioxidant power among the fractionated enzymatic hydrolysates. These results suggest that the protein hydrolysate derived from yellowfin tuna by-products and its peptide fractions could be used as an antimicrobial and antioxidant ingredient in both nutraceutical applications and functional food.

Bacterial cellulose nanofibers as reinforce in edible fish myofibrillar protein nanocomposite films.

Bacterial cellulose nanofibers (BCNF) were employed in order to improve various properties of fish myofibrillar protein (FMP) films of Silver carp. Three different levels (2, 4 and 6%, w/w) of the nanoparticles were added to the protein polymer substrate. In this regard, it became clear that 6% BCNF-containing nanocomposites had the highest tensile strength, which was about 49% better than control samples. The nanoparticles had positive impact on the physical properties; BCNF-containing films showed a reduction in water vapor permeability, swelling and solubility indexes. The results of SEM displayed uniform distribution and continuous cross-section of nanocomposite films. FTIR analysis of different films showed molecular interactions between nanoparticles and polymer substrate. XRD analysis represents the appearance of new peaks in polymer nanocomposites and the increase in crystallization of these films compared to the control film. Evaluation of thermal properties of these films suggests the improved thermal stability of the nanocomposites.

Nanoencapsulation of lemon essential oil in Chitosan-Hicap system. Part 1: Study on its physical and structural characteristics.

Lemon essential oils (LEOs) as a bioactive compound with health beneficial potential are used as safe additives in foods, medicine and nutritional supplements. However, it is a chemical compound which is sensitive to light, thermal condition and oxidation. To overcome these challenge encapsulation could be an adequate technique to protect them from degradation and evaporation. In this study, nanocapsules based on chitosan (CS) and modified starch (Hicap) with LEOs as an active ingredient was prepared by freeze-drying. The produced nanocapsules were characterized by their structural and physicochemical properties. It was found that nanocapsules produced by using CS: Hi-cap (1.5%:8.5%) clearly showed the highest encapsulation efficiency (85.44%) and Zeta potential value (+44.23mV). In vitro release studies demonstrated a prolonged release of the samples with larger CS ratio. Most nanocapsules sizes ranged from 339.3 to 553.3nm. The obtained nanocapsules showed a rough surface without the spherical shape as represented by Scanning electron microscopy images. Differential scanning calorimetry (DSC) thermogram and Fourier transform infrared (FTIR) spectroscopy techniques confirmed the success of LEOs encapsulation. The desirable physicochemical properties and thermal stability specified that such nanocapsules have promising application in delivery of LEOs in medicine and food industries.

Antimicrobial resistance of Listeria monocytogenes isolated from seafood and humans in Iran.

Fourteen Listeria monocytogenes isolates previously collected from seafood (n = 7) and human patients (n = 7) were studied for their antimicrobial susceptibility against eight common antimicrobials (ampicillin, penicillin, gentamicin, streptomycin, tetracycline, trimethoprim-sulfamethoxazole, chloramphenicol, and cefotaxime). A high resistance level to ampicillin, cefotaxime (100%), and pencillin (57% in seafood isolates and 71.4% in clinical isolates) was observed in this study. However, all of the isolates were susceptible to trimethoprim-sulfamethoxazole, chloramphenicol, and tetracycline. Simultaneous resistance was identified in 4 clinical isolates (57.1%). Genotypic characterization of fish isolates (isolated from three fish species) was performed by pulsed-field gel electrophoresis (PFGE). A high diversity among fish isolates was observed. PFGE analyses distinguished the 4 isolates into 4 reproducible pulsotypes. There was no correlation between the antibiograms with pulsotypes. In conclusion, the resistance of seafood isolates to the antibiotics commonly used to treat listeriosis could be a potential health hazard for consumers.

Comparison of chitosan-gelatin composite and bilayer coating and film effect on the quality of refrigerated rainbow trout.

The effect of chitosan-gelatin coating and film on the rancidity development in rainbow trout (Oncorhynchus mykiss) fillets during refrigerated storage (4±1 °C) was examined over a period of 16 days. Composite and bilayer coated and film wrapped fish samples were analysed periodically for microbiological (total viable count, psychrotrophic count) and chemical (TVB-N, POV, TBARS, FFA) characteristics. The results indicated that chitosan-gelatin coating and film retained their good quality characteristics and extend the shelf life of fish samples during refrigerated storage .The coating was better than the film in reducing lipid oxidation of fillets, but there was no significant difference between them in control of bacterial contamination.

Characterization of antioxidant-antimicrobial κ-carrageenan films containing Satureja hortensis essential oil.

The present work was aimed at characterizing biodegradable composite kappa-carrageenan films incorporated with Satureja hortensis (SEO) in terms of their physical, optical, mechanical, barrier and antioxidant properties. Also, in a comparative study, we sought to evaluate the antimicrobial effectiveness of these films against five pathogens. The films' water vapor barrier properties were found to improve considerably upon the addition of SEO. Carrageenan composite films were less resistant to breakage, more flexible and more opaque with lower gloss than the control film. These results can be explained by the film's microstructure, which was analyzed by atomic force microscopy and scanning electron microscopy. The films incorporating SEO showed good antioxidant properties; this effect was greatly improved when the proportion of added SEO was 3%. Films with SEO effectively inhibited the five microorganisms tested. The results of the present study suggest that SEO as a natural antibacterial agent can potentially be used in packaging a wide range of food products, particularly those that are highly oxidative and microbial sensitive.