Characterization of certain bacterial strains for potential use as starter or probiotic cultures in dairy products

The present work was aimed at characterizing 12 strains of lactic acid bacteria (LAB) to obtain improved potential starter or probiotic cultures that could be used for making dairy products from ewe's milk and cow's milk. Eight strains with antimicrobial properties, isolated from ewe's milk and from cheese made from ewe's and/or cow's milk, were studied. They were identified as Enterococcus faecalis (five strains), Lactococcus lactis subsp. cremoris, Leuconostoc mesenteroides, and Lactobacillus paracasei subsp. paracasei (one strain of each species). Additionally, four strains were obtained from the American Type Culture Collection: Lactobacillus casei 393 (isolated from cheese), L. lactis subsp. lactis 11454 (origin nonspecified and a producer of nisin), and two strains isolated from human feces (L. paracasei subsp. paracasei 27092 and Lactobacillus rhamnosus 53103, antibacterial agent producer). All E. faecalis strains showed at least one virulence factor (either hemolysin or gelatinase), which emphasizes the importance of these studies in this species. Both L. lactis strains and most Lactobacillus spp. were good acidifiers in ewe's milk and cow's milk at 30°C. High β-galactosidase activity, as well as aminopeptidase activities that favor the development of desirable flavors in cheese, were detected in all Lactobacillus spp. strains. Furthermore, L. rhamnosus ATCC 53103 showed α-fucosidase activity (thought to help colonization of the intestine) and lack of α-glucosidase activity (a trait considered positive for diabetic and obese humans). This last enzymatic activity was also lacking in L. lactis ATCC 11454. L. mesenteroides was the only strain D(2)-lactic acid producer. The selection of any particular strain for probiotic or dairy cultures should be performed according to the technological and/or functional abilities needed.     

Change in α‐tocopherol contents,lipid oxidation and fatty acid profile in eggs enriched with linolenic acid or very long‐chain ω3 polyunsaturated fatty acids after different processing methods

The influences of dietary supplementation with α‐tocopheryl acetate (α‐TA) and of processing (by hard‐boiling and scrambling) of eggs enriched with ω3 fatty acids, either very long‐chain ω3 polyunsaturated fatty acids (VLC ω3 PUFAs) or linolenic acid (LNA), on fatty acid composition, α‐tocopherol content and lipid oxidation (thiobarbituric acid (TBA) values) were studied. Four dietary treatments were formulated from a basal diet containing 40 g kg^?1 linseed oil (LO) or fish oil (FO) combined with either 0 or 100 mg α‐TA kg^?1 of feed. Eggs from LO treatments were enriched with LNA and those from FO treatments were rich in VLC ω3 PUFAs. Neither processing nor dietary supplementation with α‐TA modified greatly the fatty acid profile of eggs. Dietary supplementation with α‐TA increased the α‐tocopherol content of eggs (187.2 versus 407.9 µg g^?1 dry matter). Eggs from FO treatments showed lower α‐tocopherol content than those from LO treatments (273.5 versus 321.6 µg g^?1 dry matter), and processing of eggs enriched with VLC ω3 PUFA reduced the α‐tocopherol content by a significant 16%. Moreover, processing of eggs increased lipid oxidation two‐ to nine‐fold. Oxidation levels of hard‐boiled eggs were 30.4% higher than those of scrambled eggs. TBA values in hard‐boiled and scrambled eggs were significantly reduced when 100 mg α‐TA kg^?1 of feed supplemented the diet only in those eggs enriched with VLC ω3 PUFA (from FO treatments). Copyright © 2003 Society of Chemical Industry     

Alternate characterization technique for static random‐access memory static noise margin determination

The cell static noise margin (SNM) is widely used as a stability criterion for static random‐access memory cells design. This parameter is typically determined through electrical simulations since direct experimental characterization of SNM is not achievable. In this work, we present a methodology that provides an indirect measurement of the SNM on a per‐cell basis for six‐transistor SRAMs. It is based on combining an Adaptive Neuro‐Fuzzy Inference System (ANFIS) with circuit‐level cell experimentally measurable parameters as input variables to the tool. We show that it is possible to obtain the SNM for individual memory cells using the same experimental setup and data than that required for shmoo plot measurements. Results confirm that the SNM can be experimentally estimated with a relative error compared with electrical simulations that is below 0.5%. Copyright © 2012 John Wiley & Sons, Ltd.     

Comparison of analytical techniques for dynamic trace metal speciation in natural freshwaters

Several techniques for speciation analysis of Cu, Zn, Cd, Pb, and Ni are used in freshwater systems and compared with respect to their performance and to the metal species detected. The analytical techniques comprise the following: (i) diffusion gradients in thin-film gels (DGT); (ii) gel integrated microelectrodes combined to voltammetric in situ profiling system (GIME-VIP); (iii) stripping chronopotentiometry (SCP); (iv) flow-through and hollow fiber permeation liquid membranes (FTPLM and HFPLM); (v) Donnan membrane technique (DMT); (vi) competitive ligand-exchange/stripping voltammetry (CLE-SV). All methods could be used both under hardwater and under softwater conditions, although in some cases problems with detection limits were encountered at the low total concentrations. The detected Cu, Cd, and Pb concentrations decreased in the order DGT > or = GIME-VIP > or = FTPLM > or = HFPLM approximately = DMT (>CLE-SV for Cd), detected Zn decreased as DGT > or = GIME-VIP and Ni as DGT > DMT, in agreement with the known dynamic features of these techniques. Techniques involving in situ measurements (GIME-VIP) or in situ exposure (DGT, DMT, and HFPLM) appear to be appropriate in avoiding artifacts which may occur during sampling and sample handling.     

Excitation and damping of disturbances in cylindrical coronal loops

The excitation and damping of transversal coronal loop oscillations is studied using one-and two-dimensional models of line-tied cylindrical loops. By solving the time-dependent magnetohydrodynamic equations it is shown how an initial disturbance generated in the solar corona induces kink mode oscillations. We investigate the effect of the disturbance on a loop with a non-uniform boundary layer. In particular, a strong damping of transversal oscillations due to resonant absorption is found, such as predicted by previous works based on normal mode analysis.     

Detection, occurrence, and characterization of Escherichia coli O157:H7 from raw ewe's milk in Spain

A study was carried out in the Castilla y León region of Spain to investigate the presence of Escherichia coli O157:H7 in raw ewe's milk samples collected from several cheese factories during 1 year. All specimens were examined for E. coli O157:H7 by selective enrichment at 41.5 +/- 1.0 degrees C, after both 6 and 22 h of incubation, and then immunomagnetically separated and plated on cefixime-potassium tellurite-sorbitol MacConkey agar. No growth was obtained in the enrichment broth after a 6-h incubation. Presumptive colonies obtained after 22 h of incubation were screened by a multiplex PCR assay for the presence of rfbO157 and fliCH7 genes. Of all the ewe's milk samples studied, three were positive for E. coli O157:H7. The E. coli O157:H7 strains that were positive for the rfbO157 and fliCH7 genes were then analyzed by multiplex PCR for the presence of virulence genes (stx1, stx2, ehxA, and eaeA). All E. coli O157:H7 isolates were Shiga toxigenic and harbored additional genes related to virulence (ehxA and eaeA). The predominant Stx toxin type was stx2. These results demonstrate that raw ewe's milk used in cheesemaking may be sporadically contaminated with E. coli O157:H7 strains that are potentially pathogenic for humans.     

Jörg Kärger: Diffusion Is His Life

Jörg Kärger is a pioneer in the field of diffusion and his work has contributed significantly to the understanding of molecular mass transfer in porous systems. He has been actively researching diffusion in nanoporous materials for more than 50 years and, according to the Web of Science, is the most productive author in the field of diffusion, with 247 entries (search for diffusion in the title). He also has the highest total local citation score in the field of diffusion, which indicates not only the high number but also the high quality of his publications.     

Improvement of Poly(lactide) Ductile Properties by Plasticization with Biobased Tartaric Acid Ester

Diethyl l -tartrate (DET) is used as a biobased plasticizer for poly(lactide) (PLA) formulations with improved ductile properties without compromising biodegradation. Different weight percentages (wt.%) of DET in the 0–50 wt.% range are added to PLA by melt compounding and subsequently processed by injection molding. The effect of wt.% DET on mechanical, thermal, thermo-mechanical, morphology, biodegradation, and crystallinity is studied. Addition of 20 wt.% DET leads to a noticeable increase in elongation at break up to values of 567%, which is quite an interesting result considering the extreme brittleness of PLA. These results are verified by field emission scanning electron microscopy (FESEM) images, where filament-like structures are observed, indicative of an effective plasticization. Differential scanning calorimetry (DSC) and dynamic mechanical thermal analysis (DMTA) show that the glass transition temperature of PLA is drastically decreased down to values of 23 °C for the sample with the highest amount of DET (50 wt.%), thus increasing its ductility and processability. Fourier-transformed infrared spectroscopy (FTIR) spectra show that there exists chemical interactions between PLA and DET. Finally, the biodegradability analysis proves that the developed blends are fully biodegradable, achieving complete disintegration after 49 days. It is observed that DET enhanced the disintegration rate of PLA.     

Hot Brownian Motion of Thermoresponsive Microgels in Optical Tweezers Shows Discontinuous Volume Phase Transition and Bistability

Microgels are soft microparticles that often exhibit thermoresponsiveness and feature a transformation at a critical temperature, referred to as the volume phase transition temperature. Whether this transformation occurs as a smooth or as a discontinuous one is still a matter of debate. This question can be addressed by studying individual microgels trapped in optical tweezers. For this aim, composite particles are obtained by decorating  Poly-N-isopropylacrylamide (pNIPAM) microgels with iron oxide nanocubes. These composites become self-heating when illuminated by the infrared trapping laser, performing hot Brownian motion within the trap. Above a certain laser power, a single decorated microgel features a volume phase transition that is discontinuous, while the usual continuous sigmoidal-like dependence is recovered after averaging over different microgels. The collective sigmoidal behavior enables the application of a power-to-temperature calibration and provides the effective drag coefficient of the self-heating microgels, thus establishing these composite particles as potential micro-thermometers and micro-heaters. Moreover, the self-heating microgels also exhibit an unexpected and intriguing bistability behavior above the critical temperature, probably due to partial collapses of the microgel. These results set the stage for further studies and the development of applications based on the hot Brownian motion of soft particles.