Modelling of biological processes during aerobic treatment of piggery wastewater aiming at process optimisation

A dynamic mathematical model was developed for the simulation of the aerobic treatment of piggery wastewater. This model includes the carbon oxidation, the nitrification and the denitrification. According to the experimental results obtained during this study, a modified version of the activated sludge model No. 1 has been developed. The model includes (1) nitrite as intermediate of nitrification and denitrification, (2) the distinction between the anoxic heterotrophic yield and the aerobic heterotrophic yield, respectively equal to 0.53 and 0.6 and (3) the first-order hydrolysis of the slowly biodegradable fraction. The calibration and the validation of the model was performed using experimental data from three experiments with two piggery wastewaters. A set of kinetic and stoichiometric parameters emerged from these tests. Except the kinetic of hydrolysis of the slowly biodegradable organic matter varying from 6 to 25 gCOD(gCODday)(-1), all other parameters were similar for all experiments. The dissolved oxygen concentration was identified as the main variable influencing the nitrite accumulation during nitrification. In the calibrated model, the oxygen half-saturation coefficient of the ammonium oxidisers (0.3g O(2)m(-3)) was lower than for the nitrite oxidisers (1.1 gO(2)m(-3)), leading to nitrite accumulation when the dissolved oxygen concentration was low. Simulations with the proposed model could be very useful for improved design and management of biological treatment of piggery wastewaters, particularly in case of partial nitrification to nitrite directly followed by denitrification.     

Floristic diversity patterns in the White Carpathians biosphere reserve,Czech Republic

The flora of the White Carpathians, a mountain range in the south-east of the Czech Republic, is documented by about 485,000 records of vascular plant occurrences collected since the mid-19^th century. A total of 1299 species recorded in 93 grid cells of 2.8 × 3.1 km were used for an analysis of spatial patterns of floristic diversity in the White Carpathians. Multivariate statistical techniques such as ordination and classification were used to reveal the main gradients in floristic composition and species richness, and measured environmental data and Ellenberg indicator values were used to assess underlying environmental factors. There is a striking floristic contrast between the western and eastern part of the study area, which is associated with differences in climate, mean altitude, topographic heterogeneity measured as altitudinal range, and land use. The western part is characterised by thermophilous, continental and calcicolous species of open habitats. In contrast, the more forested eastern part along the state border with Slovakia and the north-eastern part of the area are characterised by acidophilous species with higher moisture requirements. This pattern is consistent with the established phytogeographical division of the Czech Republic into the phytogeographical regions of Thermophyticum and Mesophyticum. The further division of the area into four regions, based on classified grid data, is also similar to the current division into phytogeographical districts, except for the Javorníky district. There are two distinct hot spots of species richness, in the western and the extreme north-eastern part. A poorer flora was found in landscapes with intensive agriculture. Species richness is associated with different environmental factors than species composition, namely with soil types and land-use categories. Alien species are more common in areas with a higher incidence of arable land and built-up areas, and less common in areas dominated by grasslands and forests.     

High-level production of poly (β-<Emphasis Type="SmallCaps">l</Emphasis>-malic acid) with a new isolated <Emphasis Type="Italic">Aureobasidium pullulans</Emphasis> strain

Poly (β-l-malic acid) (PMLA) is a water-soluble polyester with many attractive properties in chemical industry and medicine development. However, the low titer of PMLA in the available producer strains limits further industrialization efforts and restricts its many potential applications. In order to solve this problem, a new strain with the distinguished high productivity of PMLA was isolated from fresh plants samples. It was characterized as the candidate of Aureobasidium pullulans based on the morphology and phylogenetic analyses of the internal transcribed spacer sequences. After the optimization of culture conditions, the highest PMLA concentration (62.27 g l⁻¹) could be achieved in the shake flask scale. In addition, the contribution of the carbon flux to exopolysaccharide (EPS) and PMLA could be regulated by the addition of CaCO₃ in the medium. This high-level fermentation process was further scaled up in the 10 l benchtop fermentor with a high PMLA concentration (57.2 g l⁻¹) and productivity (0.35 g l⁻¹ h⁻¹), which are the highest level in all the literature. Finally, the suitable acid hydrolysis conditions of PMLA were also investigated with regard to the production of l-malic acid, and the kinetics of PMLA acid hydrolysis was modeled to simulate the whole degradation process. The present work paved the road to produce this multifunctional biomaterial (PMLA) at industrial scale and promised one alternative method to produce l-malic acid in the future.     

In situ detection of calcium ions with chemically modified microcantilevers

We report a novel technique of micromechanical detection of trace amounts of calcium ions by using microcantilevers modified with ion-selective self-assembled monolayers (SAMs). The SAM-modified microcantilevers undergo bending due to selective adsorption of calcium ions. Experiments conducted under flow conditions show that the modified cantilevers respond sensitively to calcium ions (Ca(2+)); a Ca(2+) concentration of 10(-9) M can be detected with this technique. Other cations, such as Na(+) and K(+), do not have any effect on the deflection of these cantilevers. We demonstrate two different kinds of SAMs having selectivity for calcium ions.     

Biochemical isolation and purification of ovulation-inducing factor (OIF) in seminal plasma of llamas

Background  

The objective of the present study was to isolate and purify the protein fraction(s) of llama seminal plasma responsible for the ovulation-inducing effect of the ejaculate.     

Somatostatin inhibition of insulin release from freshly isolated and organ cultured rat islets of langerhans in vitro

1×10^?6M somatostatin causes a 37–44% inhibition of glucose induced insulin release from freshly isolated rat islets of Langerhans. A 81 to 95% inhibition is observed when the isolated islets are maintained in organ culture for 2 days prior to the somatostatin treatment. The dose curve of somatostatin on cultured islets shows an apparent K_I of 1.4×10^?9. The tetradecapeptide also causes a reversible inhibition of the stimulation of insulin release by 5 mM theophylline and 23 mM K⁺.     

Platelet Recruitment Promotes Keratocyte Repopulation following Corneal Epithelial Abrasion in the Mouse

Corneal abrasion not only damages the epithelium but also induces stromal keratocyte death at the site of injury. While a coordinated cascade of inflammatory cell recruitment facilitates epithelial restoration, it is unclear if this cascade is necessary for keratocyte recovery. Since platelet and neutrophil (PMN) recruitment after corneal abrasion is beneficial to epithelial wound healing, we wanted to determine if these cells play a role in regulating keratocyte repopulation after epithelial abrasion. A 2 mm diameter central epithelial region was removed from the corneas of C57BL/6 wildtype (WT), P-selectin deficient (P-sel^-/-), and CD18 hypomorphic (CD18^hypo) mice using the Algerbrush II. Corneas were studied at 6h intervals out to 48h post-injury to evaluate platelet and PMN cell numbers; additional corneas were studied at 1, 4, 14, and 28 days post injury to evaluate keratocyte numbers. In WT mice, epithelial abrasion induced a loss of anterior central keratocytes and keratocyte recovery was rapid and incomplete, reaching ~70% of uninjured baseline values by 4 days post-injury but no further improvement at 28 days post-injury. Consistent with a beneficial role for platelets and PMNs in wound healing, keratocyte recovery was significantly depressed at 4 days post-injury (~30% of uninjured baseline) in P-sel^-/- mice, which are known to have impaired platelet and PMN recruitment after corneal abrasion. Passive transfer of platelets from WT, but not P-sel^-/-, into P-sel^-/- mice prior to injury restored anterior central keratocyte numbers at 4 days post-injury to P-sel^-/- uninjured baseline levels. While PMN infiltration in injured CD18^hypo mice was similar to injured WT mice, platelet recruitment was markedly decreased and anterior central keratocyte recovery was significantly reduced (~50% of baseline) at 4–28 days post-injury. Collectively, the data suggest platelets and platelet P-selectin are critical for efficient keratocyte recovery after corneal epithelial abrasion.     

Structural consequences of the inhibitor-resistant Ser130Gly substitution in TEM beta-lactamase

Beta-lactamase confers resistance to penicillin-like antibiotics by hydrolyzing their beta-lactam bond. To combat these enzymes, inhibitors covalently cross-linking the hydrolytic Ser70 to Ser130 were introduced. In turn, mutant beta-lactamases have emerged with decreased susceptibility to these mechanism-based inhibitors. Substituting Ser130 with glycine in the inhibitor-resistant TEM (IRT) mutant TEM-76 (S130G) prevents the irreversible cross-linking step. Since the completely conserved Ser130 is thought to transfer a proton important for catalysis, its substitution might be hypothesized to result in a nonfunctional enzyme; this is clearly not the case. To investigate how TEM-76 remains active, its structure was determined by X-ray crystallography to 1.40 A resolution. A new water molecule (Wat1023) is observed in the active site, with two configurations located 1.1 and 1.3 A from the missing Ser130 Ogamma; this water molecule likely replaces the Ser130 side-chain hydroxyl in substrate hydrolysis. Intriguingly, this same water molecule is seen in the IRT TEM-32 (M69I/M182T), where Ser130 has moved significantly. TEM-76 shares other structural similarities with various IRTs; like TEM-30 (R244S) and TEM-84 (N276D), the water molecule activating clavulanate for cross-linking (Wat1614) is disordered (in TEM-30 it is actually absent). As expected, TEM-76 has decreased kinetic activity, likely due to the replacement of the Ser130 side-chain hydroxyl with a water molecule. In contrast to the recently determined structure of the S130G mutant in the related SHV-1 beta-lactamase, in TEM-76 the key hydrolytic water (Wat1561) is still present. The conservation of similar accommodations among IRT mutants suggests that resistance arises from common mechanisms, despite the disparate locations of the various substitutions.