Selection of a support for immobilization of a microbial lipase for the hydrolysis of triglycerides

Baterial lipase from Staphylococcus carnosus (pLipMut2) has been immobilized on various supports in order to determine a suitable immobilization technique in terms of activity and stability, when utilized for the hydrolysis of tributyrin. The hydrophobic materials PBA Eupergit and PBA Eupergit 250L prooved to be appropriate supports, when the enzyme was crosslinked with glutaraldehyde after adsorption. No desorption of the immobilized enzyme occured during operation. The pore size of the support has a strong effect on the activity but does not influence stability.The initial activity for immobilized and soluble lipase is found to follow the Arrhenius equation at low temperature, where mass transfer does not affect reaction kinetics. Activation energies for soluble and immobilized lipase were evaluated to be 21.7 kJ mol^–1 and 60.8 kJ mol^–1, respectively.Operational stability was studied in a packed bed recirculation reactor. Thermal desactivation followed first order kinetics with a half-life of 1340 h at 10°C. Model calculations for productivity showed, that optimal temperatures for high productivity are well below the temperature of maximal activity.List of Symbols E _a [kJ mol^–1] activation energy - E _d [kJ mol^–1] activation energy of desactivation - H [–] half-number - k _d [h^–1] desactivation constant - k _d, [h^–1] constant - k _N [–] desactivation constant (number) - N [–] number of runs - p [mol dm^–3] productivity - t [h] time - t _0.5 [h] half-life - T [K] absolute temperature - V [U ml^–1] activity - V(N) [Uml^–1] activity exhibited in the n-th run - V _s,O [U ml^–1] initial activity of supernatant - V _s, [U ml^–1] activity of supernatant after immobilization - V _O [U ml^–1] initial activity - V [U ml^–1] constant - _imm [–] activity yield - [ml ml^–1] ratio of volume of support to volume of supernatant Financial support of this work by the Deutsche Forschungsgemeinschaft (SFB 145, A15) is gratefully acknowledged.     

Preliminary assays for the development of a probiotic for goats

In order to determine probiotic properties, 137 strains of lactic acid bacteria from the feces of Creole goats were screened, only six were resistant to pH 2.0 and bile salts (0.3%). Three strains identified as Lactobacillus and two as Enterococcus showed agglutination with the treated yeast. Between them, Lactobacillus DDL17, DDL19, DDL48 and Enterococcus DDE39 demonstrated high specificity in this test because the correspondent agglutination was inhibited by one sugar, suggesting the presence of a lectin-like structure in their cell walls, which could be due to adhesion ability. Another Enterococcus strain (DDE55) showed low affinity because five sugars inhibited the agglutination of the treated yeasts. The results of hydrophobic properties showed that the strains who were able to agglutinate yeasts presented similar hydrophobic characteristics as hexadecane, xylene and toluene, but high specificity was not related to a high hydrophobicity. Only two strains (Lactobacillus DDL19 and DDL48) showed aggregation with the lowest concentration of ammonium sulfate, complementing the hydrophobicity assay. Only one strain, Lactobacillus DDL48, showed an inhibition against an enteric indicator strain (Salmonella Typhimurium and Escherichia coli O111). This inhibitory action was not affected by the addition of catalase and no inhibition was detected after neutralizing the supernatant culture fluid. These strains could be pre-selected in order to complete studies focused on designing a probiotic for use in goat feed.     

Simulation for the recovery of plasmid for a DNA vaccine

The pIDKE2 plasmid is the main component of the CIGB's candidate vaccine against Hepatitis C virus (HVC), which is being used in HCV chronically-infected individuals during clinical trials phase 1 and 2. The designed downstream process of pIDKE2 plasmid produces up to 179 g/year. In order to conduct further improvements, modelling of the downstream process was performed. A methodology based on process analysis tools, such as experimental design and modelling was established to identify factors with the highest influence on production cost and the amount of annual plasmid. Taking into account that the pIDKE2 downstream process designed is in its initial stages of development, CIM technology was evaluated as a new manufacturing process on lab scale. Purity and recovery of CIM technology was better than porous particle matrix, thus SuperPro Designer was used in order to simulate the purification process. Cost efficiency optimization of the pIDKE2 downstream process was done with the simulation model.     

On a stochastic model for the firing sequence of a neuron

A stochastic model of a neuron with excitatories and inhibitories incident on it is studied. The excitatory and the inhibitory sequences are independent renewal processes. The effect of an excitatory is to increase the membrane potential by random amounts that are independently and identically distributed, while an inhibitory causes a reset of the potential to the rest level so that the accumulation must start anew. When the potential crosses a threshold level K, the neuron fires. Immediately after this, the membrane potential returns to the rest level. An expression for the probability density function of the interval between two successive firings is derived, and special cases worked out. Graphs of the mean and the mean − √variance versus the threshold level are presented and discussed.     

Possibilities for a new breed of cattle for the south

Ohne Zusammenfassung

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Possibilities for a new breed of cattle for the south

     

A nonparametric and a parametric version of a test for the detection of the presence of a major gene applicable on data for the complete nuclear family

Summary Nonparametric and parametric tests are suggested for detecting the presence of a major gene for a quantitative trait. The model for the determination of the quantitative trait is an additive one with polygenic, family environment, and individual environment components. The power functions with respect to the major gene effect have been calculated by simulation, and the tests have therefore been compared with each other. The tests have been applied to nuclear family data on human obesity, and the results compared with those obtained using other methods on the same data.This work was done while the author was a visitor at the Istituto di Genetica Biochemica ed Evoluzionistica, CNR, Pavia     

Strengthening protected-area management: a focus for the 1990s,a platform for the future

This paper aims at an objective evaluation of the purpose, management and effectiveness of protected areas. It questions accepted dogma and poses broad challenges that need to be resolved, in order to enter the next century with a more secure, efficient and meaningful global network of parks and reserves. It also suggests the need for protected-area managers to form themselves into a discrete, focused, professional discipline, emancipated from the noise created by a professionalism borrowed from a range of other disciplines. This is central to addressing the mounting challenges facing protected areas, if they are to survive and fulfill the purposes expected of them.     

Some inequalities for the expectation of a product of functions of a random variable and for the multivariate distribution function at a random point

Under certain assumptions the expectation of a product of functions of a random variable is greater (smaller) than the product of expectations. The multivariate distribution function of m independent random variables at a random point is greater than the product of the distribution functions of the m variables.     

Development and adaptation of a multiprobe biosensor for the use in a semi-automated device for the detection of toxic algae

Worldwide monitoring programs have been launched for the observation of phytoplankton composition and especially for harmful and toxic microalgae. Several molecular methods are currently used for the identification of phytoplankton but usually require transportation of samples to specialised laboratories. For the purpose of the monitoring of toxic algae, a multiprobe chip and a semi-automated rRNA biosensor for the in-situ detection of toxic algae were developed. Different materials for the electrodes and the carrier material were tested using single-electrode sensors and sandwich hybridisation that is based on species-specific rRNA probes. Phytoplankton communities consist of different species and therefore a biosensor consisting of a multiprobe chip with an array of 16 gold electrodes for the simultaneous detection of up to 14 target species was developed. The detection of the toxic algae is based on a sandwich hybridisation and an electrochemical detection method.     

Evidence for the classification of a crayfish pathogen as a member of the genus Coxiella

AIMS: The study aimed to provide characterization of a potential new species of Coxiella, identified following a series of outbreaks of disease in Australian native freshwater crayfish. METHODS AND RESULTS: PCR primers designed for amplification of Coxiella burnetii genes including 16S rDNA, com1 and sodB were used to amplify homologues in the Coxiella-like crayfish pathogen. Products were then cloned and sequenced. The organism demonstrated a high degree of sequence homology in the highly conserved 16S rDNA (96%) and sodB (99%) genes, as well as the Coxiella sp. specific com1 (100%) gene. Regions flanking the sodB coding sequence demonstrated homology to C. burnetii antioxidant AhpC/Tsa family protein and dihydrodipicolinate reductase gene. CONCLUSIONS: The degree of homology between the genes selected and flanking regions suggested the two organisms were sufficiently closely related to belong to the same genus. SIGNIFICANCE AND IMPACT OF THE STUDY: This study provided evidence for a potential new species in the currently monospecific genus Coxiella, with the only described member being C. burnetii, a category B biological warfare agent.     

Laying the foundations for a bio-economy

Biological technologies are becoming an important part of the economy. Biotechnology already contributes at least 1% of US GDP, with revenues growing as much as 20% annually. The introduction of composable biological parts will enable an engineering discipline similar to the ones that resulted in modern aviation and information technology. As the sophistication of biological engineering increases, it will provide new goods and services at lower costs and higher efficiencies. Broad access to foundational engineering technologies is seen by some as a threat to physical and economic security. However, regulation of access will serve to suppress the innovation required to produce new vaccines and other countermeasures as well as limiting general economic growth.

Dynamics of a model for the variability of the interspike intervals in a retinal neuron

Recently, a model has been proposed to explain the statistics of the variability of interspike intervals of ganglion cells in the retina of goldfish under steady-state stimulation. In this note, it is shown that the dynamical behaviour of the model, both under steady-state and dynamical stimuli, is characterized by input-invariance of the output random process after a time transformation. This allows to study the signalprocessing properties of the model, and to test its applicability by a more complete experimental analysis.     

Bibliometric Evidence for a Hierarchy of the Sciences

The hypothesis of a Hierarchy of the Sciences, first formulated in the 19^th century, predicts that, moving from simple and general phenomena (e.g. particle dynamics) to complex and particular (e.g. human behaviour), researchers lose ability to reach theoretical and methodological consensus. This hypothesis places each field of research along a continuum of complexity and “softness”, with profound implications for our understanding of scientific knowledge. Today, however, the idea is still unproven and philosophically overlooked, too often confused with simplistic dichotomies that contrast natural and social sciences, or science and the humanities. Empirical tests of the hypothesis have usually compared few fields and this, combined with other limitations, makes their results contradictory and inconclusive. We verified whether discipline characteristics reflect a hierarchy, a dichotomy or neither, by sampling nearly 29,000 papers published contemporaneously in 12 disciplines and measuring a set of parameters hypothesised to reflect theoretical and methodological consensus. The biological sciences had in most cases intermediate values between the physical and the social, with bio-molecular disciplines appearing harder than zoology, botany or ecology. In multivariable analyses, most of these parameters were independent predictors of the hierarchy, even when mathematics and the humanities were included. These results support a “gradualist” view of scientific knowledge, suggesting that the Hierarchy of the Sciences provides the best rational framework to understand disciplines'' diversity. A deeper grasp of the relationship between subject matter''s complexity and consensus could have profound implications for how we interpret, publish, popularize and administer scientific research.     

A test for a shift in the boundary of the geographical range of a species

One predicted impact of climate change is a poleward shift in the boundaries of species ranges. Existing methods for identifying such a boundary shift based on changes in the observed pattern of occupancy within a grid of cells are sensitive to changes in the overall rate of sightings and their latitudinal distribution that are unconnected to a boundary shift. A formal test for a boundary shift is described that allows for such changes. The test is applied to detect northward shifts in the northern boundary of the Essex skipper (Thymelicus lineola) butterfly and the European goldfinch (Carduelis carduelis) in Great Britain. A shift is detected in the latter case but not in the former. Results from a simulation study are presented showing that the test performs well.     

Life cycle inventory for the production of zeolite a for detergents

Zeolite A is a crystalline aluminosilicare which has been used as a builder component in laundry detergents for many years. An LCI for the production of Zeolite A (“cradle-to-factory-gate”) was carried out on behalf of the European Zeolite producers. Data from five European production sites were collected to generate an average LCI for Zeolite A. The plants covered more than 77% of the total European production in 1993 an therefore represent an average situation. The original LCI tables show detailed figures about raw material, intermediates and auxiliary material consumption. The overall energy flow for the production of I t of anhydrous Zeolite is 22400 MJ with a minimal spread of ± 5% over the individual companies. Furthermore 25 air emission parameters and 35 water emission parameters are listed and categorised with respect to their origins e.g. process dependent, transportation, thermal energy and electricity production. Each company is able to compare their individual data with the average LCI to identify any opportunities to improve production processes. In addition, this LCI of Zeolite A provides the basis for any further LCA studies of a product containing Zeolite A, including comparisons and assessments.     

Nomograms for determining the parameters for a probabilistic model of radiosensitivity

Nomograms are introduced for the determination, from the experimental survival curves, of a and b parameters of the probabilistic model of cell radiosensitivity (proposed by Kapul'tsevich, 1978). The parameter errors are estimated too. Some examples of using these nomograms for bacteria, yeast and mammalian cells are considered.     

Searching for a photocycle of the cryptochrome photoreceptors

The initial photochemistry of plant cryptochromes has been extensively investigated in recent years. It is hypothesized that cryptochrome photoexcitation involves a Trp-triad-dependent photoreduction. According to this hypothesis, cryptochromes in the resting state contain oxidized FAD; light triggers a sequential electron transfer from three tryptophan residues to reduce FAD to a neutral semiquinone (FADH*); FADH* is the presumed signaling state and it is re-oxidized to complete the photocycle. However, this photoreduction hypothesis is currently under debate. An alternative model argues that the initial photochemistry of cryptochromes involves a photolyase-like cyclic electron shuttle without a bona fide redox reaction mediated by the Trp-triad residues, leading to conformational changes, signal propagation, and physiological responses.