Peptidase and proteinase activity ofLactococcus lactis, Lactobacillus casei andLactobacillus plantarum

The proteolytic system of several non-commercial strains of lactococci and lactobacilli that were isolated directly from traditional-Spanish, semi-hard, goats' milk cheese was studied. The aminopeptidase, X-prolyldipeptidyl aminopeptidase, dipeptidase and proteinase activity of these new strains was measured for the cytoplasmic, cell-wall/membrane and spontaneously released fractions. The aminopeptidase activity was exclusively intracellular and higher forLactobacillus casei subsp.casei than forLactococcus lactis subsp.lactis. Lactobacillus plantarum showed higher dipeptidase activity thanL. casei. The highest level of proteinase activity was recorded for the cell-wallmembrane fraction ofLactococcus lactis subsp.lactis IFPL 359, and was higher on -casein than on _s-casein for all the strains studied. These results suggest some different contribution of these strains to the proteolysis of cheese during ripening and they seem to complement each other when used together in the starter culture.

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Peptidase- und Proteinase-Aktivität vonLactococcus lactis, Lactobacillus casei undLactobacillus plantarum

Zusammenfassung Das proteolytische System von mehreren nicht kommerziellenLactococcus- undLactobacillus-Stämmen wurde direkt vom traditionellen spanischen halbfesten Ziegenmilchkäse isoliert und untersucht. Die Aktivität von Aminopeptidase, X-Prolyldipeptidylaminopeptidase, Dipeptidase and Proteinase dieser neuen Stämme wurde in cytoplasmatischen, Zellwand-Membran- und spontan freigesetzten Fraktionen gemessen. Die Aminopeptidase-Aktivität erfolgte ausschließlich intracellular und war höher fürLactobacillus casei subsp. casei als fürLactococcus lactis subsp.lactis. Lactobacillus plantarum zeigte höhere Dipeptidase Aktivität alsL. casei. Die höchsten Werte für die Proteinase-Aktivität wurden für die Zellwand-Membran-Fraktion vonLactococcus lactis subsp.lactis IFPL359 gemessen. Für alle untersuchten Stämme war die Aktivität höher bei -Casein als bei _s-Casein. Dieses Ergebnis weist auf den unterschiedlichen Einfluß dieser Stämme bei der Proteolyse von Käse während der Reifung hin. Die Stämme scheinen sich gegenseitig zu ergänzen, wenn sie gemeinsam in Starterkulturen verwendet werden.

     

Effects of different levels of fat on rheological changes and microstructure of meat batters during heat processing

Summary The effect of differences in fat content (5.3% and 20.8%) on the rheological characteristics and microstructure of meat batters in the course of heating was studied. Rheological properties were assessed using nondestructive measurements (thermal scanning rigidity monitor) and structural failure (penetration test) analyses. Microstructure was studied by scanning electron microscopy (SEM). The influence of fat content on the modulus of rigidity (G) only became evident as gel structures began to form, giving higher G values for meat batters the higher the fat content of the sample. As the temperature was raised in the product (between 40 and 70° C), penetration stress and elasticity increased. The work of penetration, on the other hand, increased between 40 and 60° C, remaining steady at higher temperatures. Analysis of the results on the basis of different treatments indicates that an increase in fat content significantly raises penetration stress, elasticity and work of penetration. Increased temperature causes the formation of a matrix structure typical of heat-induced protein gels, which became compact and determine the formation of stronger, more elastic structures. Differences in microstructure caused by fat content were more evident at low temperature (40° C).

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Auswirkungen verschiedener Fettgehalte auf die rheologischen Veränderungen und Mikrostruktur von Fleischmischungen während des Erwärmungsprozesses

Zusammenfassung Es wurde die Wirkung verschiedener Fettgehalte (5,3% und 20,8%) auf die rheologischen Eigenschaften und Mikrostruktur von Fleischbräten während des Erwärmungsprozesses untersucht. Die rheologischen Eigenschaften wurden mittels nicht zerstörender Messungen (thermal scanning rigidity monitor, TSRM) und Penetrationstests bewertet. Die Untersuchungen der MikroStruktur wurde durch Raster-Elektronenmikroskopie (REM) durchgeführt. Der Einfluß des Fettgehalts auf den Festigkeitsgleitmodul (G) wird im gleichen Ausmaß ersichtlich, in welchem die Gelstrukturen beginnen, sich zu bilden. Je höher der Fettgehalt des Bräts ist, desto größer werden die G-Werte in den Bräten. Je mehr die Temperatur des Erzeugnisses gesteigert wurde (zwischen 40 °C und 70 °C), um so mehr stiegen Penetrationdruck und Elastizität an. Obwohl sich die Penetration zwischen 40 °C und 60 °C erhöhte, blieb diese bei höheren Temperaturen konstant. Die Analyse der Ergebnisse aufgrund der Behandlungen zeigt, daß ein größerer Fettgehalt den Penetrationdruck, die Elastizität und Eindringungseffekt bedeutend erhöhen. Die Erhöhung der Temperatur verursacht die Bildung von Matrix-Strukturen, die typisch für die durch Hitze herbeigeführten Proteingele sind, deren stärkere Verdichtung die Bildung von stärkeren und elastischeren Strukturen bedeutet. Die durch die Einwirkung des Fettgehalts in der Mikrostruktur entstandenen Unterschiede scheinen bei niedriger Temperatur (40 °C) klarer hervorzutreten.

     

Peptidase and proteinase activity ofLactococcus lactis,Lactobacillus casei andLactobacillus plantarum

The proteolytic system of several non-commercial strains of lactococci and lactobacilli that were isolated directly from traditional-Spanish, semi-hard, goats' milk cheese was studied. The aminopeptidase, X-prolyldipeptidyl aminopeptidase, dipeptidase and proteinase activity of these new strains was measured for the cytoplasmic, cell-wall/membrane and spontaneously released fractions. The aminopeptidase activity was exclusively intracellular and higher forLactobacillus casei subsp.casei than forLactococcus lactis subsp.lactis. Lactobacillus plantarum showed higher dipeptidase activity thanL. casei. The highest level of proteinase activity was recorded for the cell-wallmembrane fraction ofLactococcus lactis subsp.lactis IFPL 359, and was higher on β-casein than on α_s-casein for all the strains studied. These results suggest some different contribution of these strains to the proteolysis of cheese during ripening and they seem to complement each other when used together in the starter culture.     

Ultrastructural alterations during embryonic rats' lung development caused by ozone

Ozone (O3) is an oxidizing agent that acts on phospholipids, proteins and sugars of cellular membranes producing free radicals, which cause oxidative damages. The O3 exposure has been used as a model to study oxidative stress, in which the respiratory airways represent the entrance to the organism. In this study, ultrastructural alterations were identified at the bronchiolar level during the intra-uterine lung development, using an O3 exposure model in pregnant rats during 18, 20 and 21 days of gestation. Twelve pregnant Wistar rats, six controls and six exposed to 1 ppm O3 inhalation during 12 h per day, were used. The rats were sacrificed at gestational days 18, 20 and 21; the fetuses were obtained and their lungs dissected. The ultrastructural analysis evidenced swollen mitochondria, cytoplasmic vacuolization of the epithelial cells and structural disorder caused by the oxidative stress. At gestation day 20, flake-off epithelial cells and laminar bodies in the bronchiolar lumen were observed. In the 21-gestation-day group, the mitochondria were edematous and their cristae were disrupted by the damage caused in mitochondrial membranes.     

Optimal design of Service Overlay Networks with economic and performance constraints

In the last years, Service Overlay Networks (SONs) have emerged as a promising means to address some of the issues (e.g. end‐to‐end QoS) affecting the current Internet and to favor the development and deployment of new value‐added Internet services. The deployment of an SON is a capital‐intensive investment, since bandwidth with certain QoS guarantees must be purchased from the individual network domains through bilateral Service Level Agreements. Thus, minimizing the economic cost of the logical end‐to‐end service delivery infrastructure is one of the key objectives for the SON provider. When a SON is aimed at end‐to‐end QoS provisioning, its topology must be designed so as to also satisfy the specific requirements of QoS‐sensitive applications. This paper deals with the problem of planning the SON topology in order to take into account both cost and QoS constraints. More specifically, the paper proposes a set of new algorithms for the design of an optimized SON topology, which minimizes the economic cost while simultaneously meeting bandwidth and delay constraints. A performance comparison among such algorithms is finally carried out. Copyright © 2009 John Wiley & Sons, Ltd.     

Creation of stable nanoconstrictions in metallic thin films via progressive narrowing by focused-ion-beam technique and in situ control of resistance

This work describes the use of focused-ion-beam for the fabrication of metallic nanoconstrictions on a Fe thin film with in situ monitoring of the structure’s resistance. With this approach the sequential FIB steps that are used for the gradual narrowing of the nanoconstriction are observed as changes in the measured resistance, thus providing very good control of the milling process. The FIB patterning enables precise termination of the process just before the crossover between the metallic and tunneling regimes near the conductance quantum value G₀ (G₀ = 2e²/h). Compared to previous approaches to create nanoconstrictions with focused-ion-beam, this new technique determines precisely the current direction and minimizes Ga damage at the nanoconstriction.     

Osteoconductive Performance of Carbon Nanotube Scaffolds Homogeneously Mineralized by Flow‐Through Electrodeposition

The treatment of bone lesions, including fractures, tumor resection and osteoporosis, is a common clinical practice where bone healing and repair are pursued. It is widely accepted that calcium phosphate‐based materials improve integration of biomaterials with surrounding bone tissue and further serve as a template for proper function of bone‐forming cells. Within this context, mineralization on preformed substrates appears as an interesting and successful alternative for mineral surface functionalization. However, mineralization of “true” 3D scaffolds –in which the magnitude of the third dimension is within the same scale as the other two– is by no means a trivial issue because of the difficulty to obtain a homogeneous mineral layer deposited on the entire internal surface of the scaffold. Herein, a “flow‐through” electrodeposition process is applied for mineralization of 3D scaffolds composed of multiwall carbon nanotubes and chitosan. It is demonstrated that, irrespective of the experimental conditions used for electrodeposition (e.g., time, temperature and voltages), the continuous feed of salts provided by the use of a flow‐through configuration is the main issue if one desires to coat the entire internal structure of 3D scaffolds with a homogeneous mineral layer. Finally, mineralized scaffolds not only showed a remarkable biocompatibility when tested with human osteoblast cells, but also enhanced osteoblast terminal differentiation (as early as 7 days in calcifying media).     

Low-Power Parallel Video Compression Architecture for a Single-Chip Digital CMOS Camera

A low-power, large-scale parallel video compression architecture for a single-chip digital CMOS camera is discussed in this paper. This architecture is designed for highly computationally intensive image and video processing tasks necessary to support video compression. Two designs of this architecture, an MPEG2 encoder and a DV encoder, are presented. At an image resolution of 640 × 480 pixels (MPEG2) and 720 × 576 (DV) and a frame rate of 25 to 30 frames per second, a computational throughput of up to 1.8 billion operations per second (BOPS) is required. This is supported in the proposed architecture using a 40 MHz clock and an array of 40 to 45 parallel processors implemented in a 0.2 m CMOS technology and with a 1.5 V supply voltage. Power consumption is significantly reduced through the single-chip integration of the CMOS photo sensors, the embedded DRAM technology, and the proposed pipelined parallel processors. The parallel processors consume approximately 45 mW of power resulting a power efficiency of 40 BOPS/W.