Cellular injuries of spray-dried Lactobacillus spp. isolated from kefir and their impact on probiotic properties

The injuries caused by spray drying (SD) of three potential probiotic lactobacilli isolated from kefir grains and the impact on some probiotic properties, were evaluated. Results demonstrated that Lactobacillus plantarum 83114 and L. kefir 8321 showed a slight reduction of viability (0.11 and 0.29 log CFU/ml respectively) after SD process, and L. kefir 8348 was found to be more sensitive to the process with a reduction in viability of 0.70 log CFU/ml. Neither membrane damage, evaluated by increased sensitivity to NaCl, lysozyme, bile salt and penicillin G, nor changes in acidifying activity in MRS and milk by lactobacilli were detected after SD. L. plantarum 83114 and L. kefir 8321 after SD did not lose their capacity to adhere to intestinal cells. Nevertheless, L. kefir 8348 showed a significant loss of adhesion capacity after SD. In addition, rehydrated spray-dried L. kefir 8321 retained the ability to protect against Salmonella invasion of intestinal cells. This effect was observed when L. kefir is co-incubated with Salmonella before invasion assay.This work shows that the membrane integrity evaluated by indirect methods and some probiotic properties of lactobacilli isolated from kefir did not change significantly after SD, and these powders could be used in functional foods applications.     

Mesoporous Silicates with Spherical Morphology Modified with Vanadium Highly Active in Oxidation of Cyclohexene with H2O2

Vanadium-containing mesoporous molecular sieves have been prepared by hydrothermal treatment at 373 K. These materials showed spherical morphology with a narrow particle size distribution between 2 and 4 μm. The techniques used for their physicochemical characterization were: XRD, AAS, N₂ physisorption, SEM, TEM and DR–UV–Vis spectroscopy. All the materials presented high specific surface area (>900 m²/g), characteristic of MCM-41 materials. A well-defined mesoporous structure was observed by TEM measures although there was no one-dimensional ordering of pores characteristic of such materials. Additionally, secondary mesoporosity domains were determined in the BJH size distribution. The sample synthesized with the highest content of V presented marked differences in their structural characteristics, which were attributed to the blockage of channels by the presence of nano-clusters and/or V_xO_y nano-oxides. From the DR–UV–Vis analysis, a successful incorporation of V ions to silica structure in tetrahedral coordination with oxygen of the network could be inferred. The catalytic activity of these materials was evaluated in the test reaction of cyclohexene oxidation using H₂O₂ as oxidizing agent, showing a high conversion of about 93% respect to the maximum, resulting dominant the radicalary mechanism over the direct oxidation mechanism. Apparently, the isolated V ions incorporated into the silica structure would be responsible for the high catalytic activity of these materials.     

Pulsed Light Treatment of Cut Apple: Dose Effect on Color,Structure, and Microbiological Stability

This study investigated the effect of pulsed light (PL) dose on color, microstructure, and microbiological stability of cut apples during 7-day refrigerated storage. Apples were irradiated at two different distances from the lamp (5 or 10 cm) during 2 to 100 s (2.4 to 221.1 J/cm²). Cut-apple surface exposed to high PL fluencies turned darker (lower L* values) and less green (higher a* value) than the control, and this effect was more pronounced as PL dose and/or storage time increased. On the contrary, the application of few flashes (2.4 J/cm²) allowed maintaining the original color of apples slices along storage. Light microscopy images of treated samples showed degraded walls and broken plasmalemma and tonoplast, which may explain, at least partially, the increase in browning of irradiated apples at high doses. Inactivation patterns of inoculated microorganisms depended on PL dose and the type of microorganism. After 100 s PL treatment at 5 cm, no counts were observed for Saccharomyces cerevisiae KE162, while for Escherichia coli ATCC 11229 and Listeria innocua ATCC 33090, reduction levels were 2.25 and 1.7 logs, respectively. Native microflora population was in general higher in control samples than in 10 and 60 s PL irradiated apples along the whole storage. Although the application of high PL fluencies allowed obtaining greater microbial reductions, they also promoted browning of apple. Application of PL at a dose of 11.9 J/cm² could extend the shelf life of cut apple with minimal modification in color.     

Effects of SiO<Subscript>2</Subscript> and TiO<Subscript>2</Subscript> fillers on thermal and dielectric properties of eco-friendly bismuth glass microcomposites of plasma display panels

The effects of SiO₂ (amorphous) and TiO₂ (crystalline, rutile) fillers on softening point (T _s), glass transition temperature (T _g), coefficient of thermal expansion (CTE), and dielectric constant (ɛ) of zinc bismuth borate, ZnO-Bi₂O₃-B₂O₃ (ZBIB) glass microcomposites have been investigated with a view to its use as the white back (rear glass dielectric layer) of plasma display panels (PDPs). The experimentally measured properties have also been compared with those of theoretically predicted values. Both the experimental and theoretical trends of these properties with added filler contents correlate very well. The interaction of fillers with glass which occurred during sintering at 560°C has also been monitored by XRD and FTIR spectroscopic analyses. The microstructures and distribution of fillers in the glass matrix have been analyzed by SEM images. It is observed that the fillers have partially dissolved in the glass at the firing temperature leaving some unreacted filler as residue which results in ceramic-glass microcomposites. In consideration of the desired properties of white back of PDPs, the addition of TiO₂ filler to ZBIB glass is found to be more preferable than SiO₂ filler. The addition of 10 wt% TiO₂ filler yielded T _s, T _g, CTE and ɛ values of 560°C, 480°C, 82 × 10⁻⁷/K and 14·6 which are found to meet the desired values of <580°C, <500°C, <83 × 10⁻⁷/K and <15, respectively with respect to use of PD200 glass as substrate in PDP technology.     

Kefiran antagonizes cytopathic effects of Bacillus cereus extracellular factors

Kefiran, the polysaccharide produced by microorganisms present in kefir grains, is a water-soluble branched glucogalactan containing equal amounts of D-glucose and D-galactose. In this study, the effect of kefiran on the biological activity of Bacillus cereus strain B10502 extracellular factors was assessed by using cultured human enterocytes (Caco-2 cells) and human erythrocytes. In the presence of kefiran concentrations ranging from 300 to 1000 mg/L, the ability of B. cereus B10502 spent culture supernatants to detach and damage cultured human enterocytes was significantly abrogated. In addition, mitochondrial dehydrogenase activity was higher when kefiran was present during the cell toxicity assays. Protection was also demonstrated in hemolysis and apoptosis/necrosis assays. Scanning electron microscopy showed the protective effect of kefiran against structural cell damages produced by factors synthesized by B. cereus strain B10502. Protective effect of kefiran depended on strain of B. cereus. Our findings demonstrate the ability of kefiran to antagonize key events of B. cereus B10502 virulence. This property, although strain-specific, gives new perspectives for the role of bacterial exopolysaccharides in functional foods.     

Porous cordierite-based ceramics processed by starch consolidation casting – Microstructure and high-temperature mechanical behavior

Porous cordierite-based ceramics with different microstructural features and mechanical behavior were formed by starch consolidation casting (SCC) using native potato and corn starches and sintered at 1275, 1300 and 1330 °C. The composition and microstructure of the ceramic materials were investigated via quantitative phase analysis using X-ray diffraction (with Rietveld refinement), the Archimedes method, mercury porosimetry, scanning electron microscopy and optical microscopy with stereology-based image analysis. The mechanical behavior of samples was evaluated by diametral compression tests at room temperature, 1000 and 1100 °C. The type of starch used and the sintering temperatures were the main factors determining the characteristics of the developed porous microstructures. Materials prepared with corn starch achieved the lowest porosity and the lowest values of mean chord length, mean pore distance and pore throat size. Because of these features, these materials thus presented, in general, higher values of apparent Young's modulus, elastic limit and mechanical strength than those prepared with potato starch. Despite the presence of a silicate glassy phase, both porous materials, mainly those prepared with corn starch, still enhanced the basic mechanical properties at high temperature, in particular, the mechanical strength and the apparent Young's modulus due to the special combination of the porous microstructure features.     

Controlled release on sand bed columns and biodegradability in soil of chitosan: Hydroxypropyl methylcellulose films

The main purpose of this work is to prepare and characterize films based on chitosan (Q) and hydroxypropyl methylcellulose (HPMC) blends to achieve adequate properties to be used as coating of conventional fertilizers to prolong their availability for crops. The films loaded with KNO₃ as model fertilizer were prepared by casting. Release of fertilizer was studied using sand bed columns. To quantify films durability in soil, their areas were measured in function of time. Results showed that chitosan substantially improved the durability of HPMC, lengthening its permanence in soil 900‰. Relative humidity had influence in mechanical properties. Comparing KNO₃ powder and that loaded in the film, the time of residence in the column was much lower for the powder than the second one: 4 and 56 days, respectively. Chitosan–HPMC film would be promising as polymeric coating for controlled release fertilizers taking into account field conditions. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47532.     

Effect of co‐contaminant phenol on performance of a laboratory‐scale RBC with algal‐bacterial biofilm treating petroleum hydrocarbon‐rich wastewater

BACKGROUND: Hydrocarbon degradation by algal‐bacterial systems has advantages over degradation by conventional heterotrophic systems. However, oily wastewaters often contain co‐contaminants that may inhibit the degradation of total petroleum hydrocarbons (TPH), leading to system failure. RESULTS: This paper reports the effect of phenol on treatment of wastewater containing petroleum hydrocarbons, i.e. diesel oil in a lab‐scale rotating biological contactor with biofilm consisting predominantly of Burkholderia cepacia and a freshwater algal culture. The effect of phenol loading from 0.11–0.69 g phenol m^?2 d^?1 on diesel degradation was studied with 21 h hydraulic retention time and TPH loading of 27.33 g TPH m^?2 d^?1. With increase in phenol loading, complete removal of phenol was observed. However, TPH removal decreased from 99% to 94% and significant decrease in TCOD removal was observed possibly due to biomass growth in suspension. Presence of algal culture in the biofilm made it feasible to operate the RBC at a high organic loading. The benefits included better immobilization of the bacterial culture, release of oxygen and generation of alkalinity. Lowering in pH due to accumulation of acidic intermediates formed during oil biodegradation was not observed in this study. CONCLUSION: This system can be recommended for treatment of industrial wastewaters containing TPH and phenols, with proper handling of biosolids. Copyright © 2010 Society of Chemical Industry     

Effect of high-K dielectric on differential conductance and transconductance of ID-DG MOSFET following Ortiz-Conde model

Microsystem Technologies - Differential conductance and transconductance of double-gate MOSFET are analytically computed in presence of high-K dielectric following Ortiz-Conde model....     

Treatment of hydrocarbon-rich wastewater using oil degrading bacteria and phototrophic microorganisms in rotating biological contactor: effect of N:P ratio

Treatment of hydrocarbon-rich industrial wastewater in bioreactors using heterotrophic microorganisms is often associated with various operational problems. In this study, a consortium of phototrophic microorganisms and a bacterium is developed on the discs of a rotating biological contactor (RBC) for treatment of wastewater containing diesel oil. The reactor was fed with oil degrading bacterium, Burkholderia cepacia and oil tolerant phototrophic microorganisms. After biofilm formation and acclimatization to 0.6% (v/v) diesel, continuous-mode operation was initiated at 21 h hydraulic retention time (HRT). Residual diesel in the effluent was 0.003%. Advantages of this system include good total petroleum hydrocarbon (TPH) removal, no soluble carbon source requirement and good settleability of biosolids. Biofilm observations revealed the predominance of B. cepacia and cyanobacteria (Phormidium, Oscillatoria and Chroococcus). The N:P ratio affected the relative dominance of the phototrophic microorganisms and bacterial culture. This ratio was a critical factor in determining the performance efficiency of the reactor. At 21 h HRT and organic loading of 27.33 g TPH/m2 d, the N:P ratio 28.5:1 and 38:1 both yielded high and almost comparable TPH and COD removal efficiencies. This study presents a feasible technology for the treatment of hydrocarbon-rich wastewater from petrochemical industries and petroleum refineries.