Use of gamma irradiation technology for modification of bacterial cellulose nanocrystals/chitosan nanocomposite film.

The objective of this work was to investigate the influence of different gamma ray dosages (5, 10, and 10 kGy) on the structural, mechanical, surface and barrier properties of chitosan (Ch) based nanocomposite film. The results showed gamma irradiation caused an increase in the surface hydrophobicity, water vapor permeability and sensitivity of films to water and also, yellowness and opacity of films increased, simultaneously. By increasing the irradiation doses up to 10 kGy, the mechanical properties of Ch/BCNC film was significantly enhanced. As observed by FTIR spectra, no change occurred in the chemical functional groups of the films during irradiation. XRD studies confirmed that crystallinity of films was increased after irradiation. The nanocomposite film irradiated by 10 kGy had the highest thermal stability. In conclusion, gamma radiation can be considered as a safe method for sterilization of foods and modification of Ch/BCNC film properties.

Preparation and characterization of cellulose nanocrystals from bacterial cellulose produced in sugar beet molasses and cheese whey media.

Bacterial cellulose (BC) is gaining considerable attention due to its unique physicochemical and mechanical properties. In this study, BC production by Gluconacetobacter xylinus PTCC 1734 in sugar beet molasses, cheese whey and standard Hestrin-Schramm (HS) media was evaluated. The synthesized BC was hydrolyzed by sulfuric acid to prepare bacterial cellulose nanocrystals (BCNC). The results showed that treated sugar beet molasses led to the highest BC concentration and productivity, followed by treated cheese whey. Structural analysis of BC and BCNC was carried out by Fourier Transform Infrared (FTIR) spectroscopy. The crystallinity index of the BCNC determined by X-ray diffraction (XRD) was higher than BC. The morphological analysis carried out by FE-SEM showed that microfibrils diameter decreases with acid treatment. TEM images confirmed the formation of rod like cellulose nanocrystals having an average diameter and length of 25 ±â€¯5 and 306 ±â€¯112 nm, respectively. In conclusion, food industrial byproducts can be used as cost-effective culture media to produce BC for large-scale industrial production and isolated cellulose nanocrystals are useful in the fabrication of bio-nanocomposite films for food packaging applications.

Physico-mechanical and antimicrobial properties of tragacanth/hydroxypropyl methylcellulose/beeswax edible films reinforced with silver nanoparticles.

The novel trinary bio-composite film based on Tragacanth/Hydroxypropyl methylcellulose/Beeswax reinforced silver nanoparticles (AgNPs) was developed. This study investigated the effect of AgNPs (2, 4 and 8%) on some physico-mechanical and antimicrobial properties of bio-composite film. It was discovered that AgNPs reduced the composite tensile strength from 33.64 to 16.12 MPa. However, water vapor permeability was improved by addition of the nanoparticles (4.57-2.16 × 10-13 g m/m2 s Pa). The use of AgNPs influenced the apparent color of bio-composite film. The microscopic surface structure and topography of the films were also examined by scanning electron microscopy and Fourier transform infrared, respectively. Dynamic mechanical thermal analysis results showed that the thermal stability of film was slightly decreased through incorporation with AgNPs. Finally, nano-composite films demonstrated strong antibacterial activity against tested pathogen bacteria in the contact surface zone. The antimicrobial results suggest that new nanocomposite film may be used as food active packaging.

Inulinase immobilized gold-magnetic nanoparticles as a magnetically recyclable biocatalyst for facial and efficient inulin biotransformation to high fructose syrup.

To date, the high cost of enzyme production, lack of enzyme reusability and operational stability are the main limitations of the enzyme's application in industry. In this work, inulinase was covalently immobilized on the surface of glutathione-coated gold magnetic nanoparticles (GSH-AuMNPs). The synthesized NPs were fully characterized. The effects of different restriction factors such as substrate concentration, temperature, and pH on the performance and stability of the enzyme were examined. The maximum activity and immobilization yield were estimated 83% and 93%, respectively. The immobilized inulinase showed maximum activity at pH 4.5 and 60 °C. The kinetic parameters of the immobilized enzyme were not changed significantly after the immobilization process. The reusability assessment indicated that approximately 78% of the initial activity of immobilized inulinase remained after ten times recycling. The storage stability of inulinase was improved by the immobilization process. The inulin hydrolysates were checked by HPLC and the end products only contained two components, 98% of fructose and up to 2% of glucose in both free enzyme and immobilized enzyme systems. This study introduced a simple, effective and inexpensive immobilization process, which is applicable in different biomedical, biotechnological and food industries.

Exopolysaccharides production by Lactobacillus acidophilus LA5 and Bifidobacterium animalis subsp. lactis BB12: Optimization of fermentation variables and characterization of structure and bioactivities.

In this study, the most important variables (incubation temperature, fermentation time and yeast extract concentration) responsible for the exopolysaccharides (EPSs) production by Lactobacillus acidophilus LA5 and Bifidobacterium animalis subsp. lactis BB12 were screened. The EPSs synthesize by LA5, BB12, and their co-culture were successfully optimized and were 349.82 ±â€¯5.39, 146.83 ±â€¯3.99 and 187.02 ±â€¯1.54 mg/L, respectively. GC-MS analysis indicated that the purified EPSs are heteropolysaccharide and consisted of glucose, galactose, glucuronic acid, and xylose. The FT-IR analysis was used to investigate functional groups of purified EPSs and NMR analysis was used to study the structure of them. The DSC, TGA and DTG analysis of the extracted EPSs showed that they had high thermal stability and degradation temperature. The results of bioactivity analysis indicated that maximum DPPH and hydroxyl radicals scavenging activity were 59.30 ±â€¯1.95, 56.76 ±â€¯0.79, 62.33 ±â€¯1.02% and 59.94 ±â€¯1.68, 46.40 ±â€¯0.73, 53.54 ±â€¯0.76%, respectively for the EPSs of LA5, BB12, and their co-culture. Additionally, reducing power of the produced EPSs by LA5, BB12, and their co-culture were 1.047 ±â€¯0.001, 1.270 ±â€¯0.045 and 1.139 ±â€¯0.018, respectively. Consequently, all these results showed that the EPSs produced by LA5, BB12, and their co-culture had a high potential as natural antioxidants or bioactive additive in the food industry.

Glutathione decorated gold-magnetic nanoparticles: efficient and recyclable catalyst for biotechnological and pharmaceutical applications.

Nowadays, since the core-shell gold-magnetite nanoparticles include the saturation magnetisation (iron oxide) and plasmon surface (gold shell) properties, they have been considered in biological and biomedicine research areas. In the present work, multifunctional glutathione decorated gold-coated iron oxide nanoparticles (GSH-AuMNPs) were successfully synthesised and fully characterised. From the absorption peak at 525, the formation of the core-shell GSH-AuMNPs was confirmed. Although the saturation magnetisation value was slightly decreased during the formation process, they were easily recovered through magnetic decantation. The biocompatibility of the synthesised NPs was approved by the cytotoxicity researches. Furthermore, the GSH-AuMNPs indicated a good catalytic activity for the catalytic reduction of 2-nitrophenol by sodium borohydride and reused for six consecutive cycles without a significant decrease in its activity. Overall, this study introduced a unique structure with high catalytic activity, which could provide a useful platform for the biomedical, analytical, catalytic applications and wastewater treatment.