Application of dextran from lactic acid bacteria for silver nanoparticles synthesis and edible coating production

Predmet istraživanja ove doktorske disertacije je izolovanje bakterija mlečne kiseline iz zrna vodenog kefira, u cilju sinteze dekstrana, kao i ispitivanje mogućnosti primene dobijenog dekstrana za sintezu nanočestica srebra i proizvodnju jestivih filmova...The scope of this doctoral dissertation is the isolation of dextran producing lactic acid bacteria from the water kefir grain and testing the possibility of the obtained dextran for silver nanoparticles synthesis and edible film's production..

Application of dextran from lactic acid bacteria for silver nanoparticles synthesis and edible coating production

Predmet istraživanja ove doktorske disertacije je izolovanje bakterija mlečne kiseline iz zrna vodenog kefira, u cilju sinteze dekstrana, kao i ispitivanje mogućnosti primene dobijenog dekstrana za sintezu nanočestica srebra i proizvodnju jestivih filmova...The scope of this doctoral dissertation is the isolation of dextran producing lactic acid bacteria from the water kefir grain and testing the possibility of the obtained dextran for silver nanoparticles synthesis and edible film's production..

Effective valorisation of barley bran for simultaneous cellulase and beta-amylase production by Paenibacillus chitinolyticus CKS1: Statistical optimization and enzymes application

The agricultural raw industry generates large amounts of annually by-products that create disposal problems. Hitherto, there have been no reported papers about the simultaneous production of cellulase and beta-amylase from these raw materials using Paenibacillus sp. that would reduce the costs. Thus, in this paper simultaneous cellulase (CMC-ase and avicelase) and beta-amylase production using barley bran and the application of the natural isolate Paenibacillus chitinolyticus CKS1 and potential enzymes in the hydrolysis process was studied. Response surface methodology was used to obtain the maximum enzyme activity (CMC-ase 0.405 U mL(-1), avicelase 0.433 U mL(-1) and beta-amylase 1.594U mL(-1)). Scanning electron microscopy showed degradation of the lignocellulosic-starch structure of barley bran after fermentation. The CKS1 bacterial supernatant, which contains cellulases and beta-amylase, could hydrolyze cotton fibres and barley bran, respectively. The main products after enzymatic hydrolysis of cotton fibres and barley bran, glucose (0.117 (-1)(g gmat)) and maltose (0.347 (-1)(g gmat)), were quantified by high performance liquid chromatography (HPLC). The produced enzymes could be used for hydrolysis of cotton fabric and barley bran to glucose and maltose, respectively. Application of simultaneous enzymes production using an agricultural by-product is economically and environmentally accepted and moreover, valuable biotechnological products, such as glucose and maltose, were obtained in this investigation

Antibacterial ability of immobilized silver nanoparticles in agar-agar films co-doped with magnesium ions

The antibacterial ability of in situ prepared nanometer-sized silver particles, immobilized in agar-agar films, was studied as a function of the concentration of co-dopant, magnesium ions. Content of inorganic components in hybrid films was determined using inductively coupled plasma optic emission spectroscopy, and found to be low (<2 wt.-%). Morphology of prepared hybrid films, studied by transmission electron microscopy, revealed the presence of non-agglomerated and randomly distributed 10–20 nm silver nanoparticles (Ag NPs) within the agar-agar matrices. Fourier-transform infrared spectroscopy indicated the distinct chemical interaction between Ag NPs and polymer chains. Thermogravimetric analysis, as well as the determination of tensile strength, Young's modulus, and elongation at break showed improvement of thermal stability and mechanical properties of agar-agar matrices upon the incorporation of Ag NPs due to high compatibility between the hydrophilic organic component and inorganic components. The complete microbial reduction of Gram-positive bacteria Staphylococcus aureuswas observed for all agar-silver films, while satisfactory results were observed for Gram-negative bacteria Pseudomonas aeruginosa (≥99.6%). The release of Ag+ ions is suppressed by the increase of the concentration of Mg2+ ions and it was found to be significantly smaller (≤0.24 ppm) than the harmful ecological level (1 ppm). © 2019 Elsevier Lt