Miona G. Miljković

Impregnation of cotton fabric with silver nanoparticles synthesized by dextran isolated from bacterial species Leuconostoc mesenteroides T3.

This study was aimed to highlight the possibility of cotton fabric impregnation with silver nanoparticles synthesized by dextran isolated from Leuconostoc mesenteroides T3 in order to obtain antimicrobial properties. The fabrication of dextran was proved by FTIR spectroscopy. Particle sizes of synthesized dextran and silver nanoparticles were measured by dynamic light scattering method. The presence of silver nanoparticles on the surface of cotton fabric was confirmed by scanning electron microscopy, X-ray diffraction measurements and reflectance spectrophotometry. Antimicrobial activity of cotton fabric impregnated with silver nanoparticles was tested against bacteria Escherichia coli and Staphylococcus aureus, and fungus Candida albicans. The results indicated that synthesized silver nanoparticles can provide satisfactory antimicrobial activity. However, maximum reduction (99.9%) of all tested microorganisms can be obtained only when 1.0mmolL(-1) colloid consisting of silver nanoparticles is applied.

β-Amylase production from packaging-industry wastewater using a novel strain Paenibacillus chitinolyticus CKS 1

Transport packaging factories generate a large amount of wastewater that contains residuals of starch glue. These residuals could be used as substrates for microorganism growth and enzyme production. In this study, β-amylase production using a new strain Paenibacillus chitinolyticus CKS1 was optimized using wastewater from a Serbian transport packaging factory. The optimization of β-amylase production was carried out using Response Surface Methodology (RSM). A Central Composite Design under the RSM with four interacting parameters (incubation time, inoculum concentration, casein hydrolysate concentration and yeast extract concentration) was employed to identify the optimal conditions for maximum β-amylase activity (334.20 U L−1) as 62 h of incubation with 2.40% inoculum, 2.02 g L−1 casein hydrolysate and 3.98 g L−1 yeast extract. High performance liquid chromatography showed that the P. chitinolyticus CKS1 strain hydrolyzed starch to form maltose as a major product. Due to the application of wastewater as an inexpensive material for enzyme and maltose production it may be considered that the economic and eco-friendly aspects of this method are very promising.

Immobilization of dextransucrase on functionalized TiO 2 supports

The TiO2 based hybrid supports with different functional groups (amino, glutaraldehyde or epoxy) were prepared and their influence on immobilization of dextransucrase (DS) was studied. Novel synthetic route for surface modification of TiO2 with amino and glutaraldehyde groups was developed taking advantage of charge transfer complex (CTC) formation between surface Ti atoms and salicylate-type of ligand (5‑aminosalicylic acid (5-ASA)). The proposed coordination of 5-ASA to the surface of TiO2 powder and optical properties of CTC was presented. The pristine TiO2 and amino functionalized TiO2 have higher sorption capacity for DS (12.6 and 12.0mgg-1, respectively) compared to glutaraldehyde and epoxy activated supports (9.6 and 9.8mgg-1, respectively). However, immobilized enzyme to either glutaraldehyde or epoxy functionalized TiO2 have almost two times higher expressed activities compared to pristine TiO2 support (258, 235 and 142IUg-1, respectively). Thermal stability of enzyme immobilized on glutaraldehyde and epoxy functionalized supports was studied at 40°C, as well as operational stability under long-run working conditions in repeated cycles. After five cycles, DS imobilized on glutaraldehyde activated support retained almost 70% of its initial expressed activity, while, after five cycles, performance of DS immobilized on epoxy activated support was significantly lower (15%).

Response surface methodology for optimisation of edible coatings based on dextran from Leuconostoc mesenteroides T3

The aim of this study was to develop dextran-based edible films plasticized by sorbitol. In order to optimise the film-forming formulation, response surface methodology was used. The influence of dextran and sorbitol concentration on the mechanical and water vapour barrier properties of obtained films was investigated. The results showed that both parameters exhibited significant effect on the water vapour permeability of a film. Both dextran and sorbitol concentration had significant influence on tensile strength and elongation at break, whereas only sorbitol concentration had significant effect on Youngs modulus. After optimisation by desirability approach, it was found that a film made of 3.40 wt% of dextran and 20.43 wt% of sorbitol showed the lowest water vapour permeability and the highest tensile strength and elasticity.