Synthesis of CaOSiO2 compounds and their testing as heterogeneous catalysts for transesterification of sunflower oil

The powder mixtures of calcium oxide (CaO) and silica gel (SiO₂) in molar ratios of 1:1, 1.5:1, 2:1 and 3:1 were mechanochemically treated with the addition of water, and were subsequently calcined with a goal of synthesizing CaSiO_3, Ca₃Si₂O₇, Ca₂SiO₄ compounds and CaO/Ca₂SiO₄ two-phase mixture. The prepared materials were characterized by XRD, FTIR, SEM/EDS, particle size laser diffraction (PSLD), UV–vis diffuse reflectance spectroscopy (DRS), N₂ adsorption/desorption isotherms, Hammett indicator for basic strength and volumetric analysis for free CaO content. The catalytic activity of calcium silicates with different Ca/Si ratios was tested in the transesterification of triacylglycerols (sunflower oil) with methanol. Samples obtained with initial composition 2CaO·SiO₂ and 3CaO·SiO₂ calcined at 700?°C, and 3CaO·SiO₂ calcined at 900?°C had high catalytic activity, resulting with triacylglycerols conversion and fatty acids methyl ester formation (FAME or biodiesel) above 96%. The activity of these samples can be attributed to the existence of free CaO defined by CaO/Ca₂SiO₄ complex mixture. The effect of different amount of catalyst used for transesterification (0.2–2?wt%) was analyzed using the most active catalyst i.e. 3CaO·SiO₂ calcined at 700?°C as well as possibility of its reuse for biodiesel synthesis. It was also found that CaSiO₃, Ca₃Si₂O₇ and Ca₂SiO₄, phases did not possess catalytic activity.     

Modified quadratic loss function for a trivariate response with the exact feasible region for parameters

This paper deals with modification of Taguchi's quadratic quality loss function (QQLF) for a trivariate responses, each having a NtB (nominal-the-best) type quality characteristic and correlated in pairs. It tends to improve and extend results obtained in 0025 and 0035. Impossibility to solve nonlinear constraint in [6] resulted in an approximate algorithm to determine unknown parameters of QQLF. Here the nonlinear constraint is solved analytically and consequently the exact feasible region is obtained. The QQLF is formed by means of the parameters from the restrictive feasible region and proved suitable for all the types of correlation among quality characteristics.     

Veterinary drug residues determination in raw milk in Croatia

A total of 1259 raw milk samples were examined over a three-year period for various antibiotics chloramphenicol, penicillins, cephalosporines, tetracyclines, sulfonamides, beta-lactams, quinolones, aminoglycosides and macrolides. Microbiological and immunoassay methods used for determination of these antibiotics were validated according to the guidelines laid down by European Commission Decision 2002/657/EC. Microbiological screening detected 36 positive samples and in only one sample presence of residues was confirmed. Also, immunoassay determination found one positive sample on tetracycline residues. In total, 37 positive samples were determined, which was equal to a frequency of 0.69% of the total number of targeted analyses. The HPLC-DAD method confirmed the presence of residues above the maximum residue limits (MRLs) in two samples with concentrations of 12 μg kg^?1 for penicillin G and 19 μg kg^?1 for amoxicillin, and 1671 μg kg^?1 for tetracycline. Calculated estimated daily intakes (EDIs) for antibiotics presented showed lower exposure levels than the fixed values of acceptable daily intakes (ADIs). These suggested that raw milk in Croatia contain very low levels of veterinary drugs so that toxicological risk with regard to consuming of milk could not be considered as a public health problem.     

Register of hazardous materials in printing industry as a tool for sustainable development management

The paper explains the concept of pollutants register. The studies are in the domain of printing industry as a relatively low source of environmental polluter, and the presented concepts, methodology and results represent the contribution to the sustainable development management. Method of data collection, compilation of the printing pollution register as well as classification of harmful substances which are emitted during the printing process is presented. Furthermore, the paper analyzes the result of the quantitative identification of hazardous substances emitted in printing industry of Novi Sad.     

Host-pathogen interactions in bovine mammary epithelial cells and HeLa cells by Staphylococcus aureus isolated from subclinical bovine mastitis

Staphylococcus aureus is a common pathogen that causes subclinical bovine mastitis due to several virulence factors. In this study, we analyzed S. aureus isolates collected from the milk of cows with subclinical mastitis that had 8 possible combinations of bap, icaA, and icaD genes, to determine their capacity to produce biofilm on biotic (bovine primary mammary epithelial cells and HeLa cells) and abiotic (polystyrene microplates) surfaces, and their ability to adhere to and invade these cells. We also characterized isolates for microbial surface components recognizing adhesive matrix molecules (MSCRAMM) and agr genes, and for their susceptibility to cefquinome sulfate in the presence of biofilm. All isolates adhered to and invaded both cell types, but invasion indexes were higher in bovine primary mammary epithelial cells. Using tryptic soy broth + 1% glucose on abiotic surfaces, 5 out of 8 isolates were biofilm producers, but only the bap⁺icaA⁺icaD⁺ isolate was positive in Dulbecco's Modified Eagle's medium. The production of biofilm on biotic surfaces occurred only with this isolate and only on HeLa cells, because the invasion index for bovine primary mammary epithelial cells was too high, making it impossible to use these cells in this assay. Of the 5 biofilm producers in tryptic soy broth + 1% glucose, 4 presented with the bap/fnbA/clfA/clfB/eno/fib/ebpS combination, and all were protected from cefquinome sulfate. We found no predominance of any agr group. The high invasive potential of S. aureus made it impossible to observe biofilm in bovine primary mammary epithelial cells, and we concluded that cells with lower invasion rates, such as HeLa cells, were more appropriate for this assay.     

Binding affinity between dietary polyphenols and β-lactoglobulin negatively correlates with the protein susceptibility to digestion and total antioxidant activity of complexes formed

Non-covalent interactions between β-lactoglobulin (BLG) and polyphenol extracts of teas, coffee and cocoa were studied by fluorescence and CD spectroscopy at pH values of the gastrointestinal tract (GIT). The biological implications of non-covalent binding of polyphenols to BLG were investigated by in vitro pepsin and pancreatin digestibility assay and ABTS radical scavenging activity of complexes formed. The polyphenol–BLG systems were stable at pH values of the GIT. The most profound effect of pH on binding affinity was observed for polyphenol extracts rich in phenolic acids. Stronger non-covalent interactions delayed pepsin and pancreatin digestion of BLG and induced β-sheet to α-helix transition at neutral pH. All polyphenols tested protected protein secondary structure at an extremely acidic pH of 1.2. A positive correlation was found between the strength of protein–polyphenol interactions and (a) half time of protein decay in gastric conditions (R² = 0.85), (b) masking of total antioxidant capacity of protein–polyphenol complexes (R² = 0.95).