Functional characterization of tobacco (Nicotiana benthamiana) serotonin N-acetyltransferases (NbSNAT1 and NbSNAT2)

Nicotiana benthamiana (tobacco) is an important dicotyledonous model plant; however, no serotonin N-acetyltransferases (SNATs) have been characterized in tobacco. In this study, we identified, cloned, and characterized the enzyme kinetics of two SNAT genes from N. benthamiana, NbSNAT1 and NbSNAT2. The substrate affinity (Km) and maximum reaction rate (Vmax) for NbSNAT1 were 579 µM and 136 pkat/mg protein for serotonin, and 945 µM and 298 pkat/mg protein for 5-methoxytryptamine, respectively. Similarly, the Km and Vmax values for NbSNAT2 were 326 µM and 26 pkat/mg protein for serotonin, and 872 µM and 92 pkat/mg protein for 5-methoxytryptamine, respectively. Moreover, we found that NbSNAT1 and NbSNAT2 localized to chloroplasts, similar to SNAT proteins from other plant species. The activities of the NbSNAT proteins were not affected by melatonin feedback inhibition in vitro. Finally, transgenic tobacco plants overexpressing either NbSNAT1 or NbSNAT2 did not exhibit increased melatonin levels, possibly due to the expression of catabolic enzymes. Generating transgenic tobacco plants with downregulated NbSNAT expression would provide further insight into the functional role of melatonin in tobacco plants.

pH-Based Control Strategies for the Nitrification of High-Ammonium Wastewaters

Aquatic nitrogen pollution is one of the most urgent environmental issues requiring prevention and mitigation. Large quantities of high-ammonium wastewaters are generated by several industrial sectors, such as fertilizer and anaerobic-digestion plants. Nitrification of these wastewaters is commonly carried out, either to remove nitrogen or produce liquid fertilizers. Standard control methodologies for the efficient nitrification of high-ammonium wastewaters to produce liquid fertilizers have not yet been established and are still within their early stages of development. In this paper, novel pH-based control algorithms are presented that maintain operation at the microbial maximum reaction rate (υmax) in batch and continuous reactors. Complete conversion of ammonium to nitrate was achieved in a batch setup, and a conversion of 93% (±1%) was achieved in a continuously-stirred-tank-reactor. The unparalleled performance and affordability of the control schemes proposed offer a steppingstone to the future of sustainable fertilizer production.

Photocatalytic ozonation in an immersion rotary body reactor for the removal of micro-pollutants from the effluent of wastewater treatment plants

Carrier-bound titanium dioxide catalysts were used in a photocatalytic ozonation reactor for the degradation of micro-pollutants in real wastewater. A photocatalytic immersion rotary body reactor with 36 cm disk diameter was used, which was irradiated using UV-A LEDs. The rotating disks were covered with catalysts based on stainless steel grids coated with titanium dioxide. The dosing of ozone was carried out through the liquid phase via an external enrichment and a supply system transverse to the flow direction. The influence of irradiation power and ozone dose on the degradation rate for photocatalytic ozonation was investigated. In addition, the performance of the individual processes photocatalysis and ozonation were studied. The degradation kinetics of the parent compounds were determined by LC-MS/MS. First-order kinetics were determined for photocatalysis and photocatalytic ozonation. A maximum reaction rate of the reactor was determined, which could be achieved by both photocatalysis and photocatalytic ozonation. At a dosage of 0.4 mg /mg DOC, the maximum reaction rate could be achieved using 75% of the irradiation power used for sole photocatalysis, allowing increases in the energetic efficiency of photocatalytic wastewater treatment processes. The process of photocatalytic ozonation is suitable to remove a wide spectrum of micro-pollutants from wastewater. HIGHLIGHT within the work, reaction rates for the degradation of micropollutants in real wastewater matrix are presented. due to the number of investigated pollutants as well as the practical investigation conditions, a more precise evaluation of the use of photocatalysis and photocatalytic ozonation for wastewater treatment is possible.

Selective and predicable amine conjugation sites by kinetic characterization under excess reagents

The site selectivity for lysine conjugation on a native protein is difficult to control and characterize. Here, we applied mass spectrometry to examine the conjugation kinetics of Trastuzumab-IgG (Her-IgG) and α-lactalbumin under excess linker concentration ([L]0) based on the modified Michaelis–Menten equation, in which the initial rate constant per amine (kNH2 = Vmax/NH2/KM) was determined by the maximum reaction rate (Vmax/NH2) under saturated accessible sites and initial amine–linker affinity (1/KM). Reductive amination (RA) displayed 3–4 times greater Vmax/NH2 and a different panel of conjugation sites than that observed for N-hydroxysuccinimide ester (NHS) chemistry using the same length of polyethylene glycol (PEG) linkers. Moreover, faster conversion power rendered RA site selectivity among accessible amine groups and a greater tunable range of linker/protein ratio for aldehyde-linkers compared to those of the same length of NHS-linkers. Single conjugation with high yield or poly-conjugations with site homogeneity was demonstrated by controlling [L]0 or gradual addition to minimize the [L]0/KM ratio. Formaldehyde, the shortest aldehyde-linker with the greatest 1/KM, exhibited the highest selectivity and was shown to be a suitable probe to predict conjugation profile of aldehyde-linkers. Four linkers on the few probe-predicted hot spots were elucidated by kinetically controlled RA with conserved drug efficacy when conjugated with the payload. This study provides insights into controlling factors for homogenous and predictable amine bioconjugation.

Cardiovascular catheter stiffness – a static measurement approach

Catheters are widely used for therapeutic and diagnostic purposes in various medical applications. Along with frictional properties as well as the catheter profile the catheter stiffness mainly affects the deliverability and thus, the handling properties of the catheter. Within this study the bending stiffness of proximal and distal catheter samples was investigated with a custom made test setup. In particular, the influence of the catheter clamping length on the test results is discussed. Bending stiffness was calculated directly from the measured force, deflection and clamping length considering the test setup compliance. Measurements were performed three times at five positions in circumferential direction. Measured bending stiffness ranged from 629 ± 31 Nmm² to 733 ± 58 Nmm² for the proximal samples and from 30 ± 5 Nmm² to 98 ± 30 Nmm² for the distal samples, respectively. Bending stiffness varied depending on the free catheter length and the reaction force measured. The maximum reaction force decreased with increasing free catheter length leading to a higher measurement uncertainty. However, when considering the same free catheter length quantitative results were similar within the group of proximal and distal samples, respectively.

INVESTIGATION OF SYNTHESIS PARAMETERS OF ANTIMONY FLUOROBORATE AND ITS USABILITY AS A FLAME RETARDANT FOR CELLULOSIC FABRICS

In this study, the synthesis parameters of antimony fluoroborate, one of the metal fluoroborates, from antimony trioxide and fluoroboric acid by the wet method, and its usability as flame retardant for cellulosic fabrics have been investigated. The maximum reaction yield was determined depending on the mole ratio of reactants, temperature and stirring speed. The characterization of the product was performed by XRD and FTIR analyses. Antimony fluoroborate was produced with 94% yield at a mole ratio of reactants (nHBF4/nSb2O3) of 6:1, at 70 °C and 300 rpm. The thermal behaviors of untreated fabric and fabric impregnated with antimony fluoroborate solution were analyzed by TGA. The flame retardancy performance of antimony fluoroborate for cellulosic fabrics was determined by the vertical flame test and the limiting oxygen index (LOI) test methods. The results show that impregnating cellulosic fabrics with antimony fluoroborate enhances their thermal stability and flame retardancy.

Study on optimization of ternary complex of piroxicam-β-cyclodextrin-lysine inclusion in supercritical CO2

Piroxicam is a bioactive compound classified as a non-steroidal anti-inflammatory drug (NSAID). However, its low solubility in water imposes a serious limitation for its application in the pharmaceutical industry. Using cyclodextrins to form complexes can enhance the dissolution rate, solubility, and bioavailability of piroxicam. In this study, piroxicam/β-cyclodextrin complexes are prepared in supercritical carbon dioxide (SC-CO2) in the solid state and the process was optimized using response surface methodology (RSM). UV-Vis spectroscopy, differential scanning calorimetry (DSC), Fourier-transform infrared spectroscopy (FTIR), and dissolution profile in water were used to characterized the complex under optimized temperature, residence time, moisture, and ternary agent. Finally, the maximum reaction yield of the inclusion complex was predicted to be 95% at the optimal conditions of 266 bar, 136oC, 1.84:1 ratio of cyclodextrin:piroxicam, and 1.5:1 ratio of lysine:piroxicam. Large scale production of inclusion complexes can be developed from the results of this work on optimizing conditions.

Derivation of volatile fatty acids concentration-independent optimum trace elements configuration and elucidation of optimization kinetics of biomethanization processes

Trace elements (TEs) requirements for improved volatile fatty acids (VFA) degradation during biomethanization depend on VFA concentration of a reactor and the temperature of the process. While temperature remains relatively constant, VFA concentrations change in the course of biomethanization and this implies that for efficient VFA degradation, different trace elements configurations (TEC) should be supplemented. While this is the most efficient approach, it is impractical and constitutes a challenge for the effective use of TEs in the optimization of biomethanization processes. To alleviate this challenge, we modelled the biomethanization efficiency of various VFA concentration-dependent (VCD) TEs configuration as scenarios and derived a TEs configuration that produced optimum biomethanization across a wider range of VFA concentrations. The study was carried out at 37oC using different concentrations of fixed VFA composition and TEs configurations as scenarios. Response surface model and desirability function were used to determine and compare the biomethanization efficiency of the scenarios, and to derive a VFA concentration-independent (VCI) TEs configuration. Michaelis-Menten kinetics for two parameters was used to ascertain that the mechanism by which TEs supplementation enhanced mesophilic biomethanization was through an increase in maximum reaction rate (MRR). However, the enhancement was accompanied by an insignificant decline in inverse affinity (IA).

CO2-Derived Carbon Capture Using Microalgae and Sodium Bicarbonate in a PhotoBioCREC Unit: Kinetic Modeling

By converting bicarbonates via Chlorella vulgaris photosynthesis, one can obtain valuable biofuel products and find a route toward carbon-derived fossil fuel conversion into renewable carbon. In this research, experiments were carried out in the PhotoBioCREC prototype under controlled radiation and high mixing conditions. Sodium bicarbonate (NaHCO3) was supplied as the inorganic carbon-containing species, at different concentrations, in the 18 to 60 mM range. Both the NaHCO3 concentrations and the organic carbon concentrations were quantified periodically during microalgae culture, with the pH being readjusted every day to the 7.00 level. It was found that sodium bicarbonate was converted with a selectivity up to 33.0% ± 2.0 by Chlorella vulgaris. It was also observed that the inorganic carbon conversion was 0.26 ± 0.09 day−1, while the maximum reaction rate constant for organic carbon formation was achieved with a 28 mM NaHCO3 concentration and displayed a 1.18 ± 0.05 mmole L−1 day−1 value.

Synthesis and Infrared Performance of SiB6 Powder through “Chemical Oven” Self-Propagating Combustion

SiB6 powders were prepared by the “chemical oven” method from Si and B powders. Here combustion with acid pickling “two-step” mode replaces the traditional synthesis method which helps to avoid severe condition of high temperature and high pressure. It could realize maximum reaction temperature to about 2000°C, and the whole process just needs ∼30 s. The average diameter of products is ∼10 μm. And the raw material Si and B are ∼3 μm and ∼20 μm, respectively. The infrared emissivity of products was evaluated by UV-vis spectrum with absorption band around 250∼2500 nm. All five samples show higher emissivity over UV-visible light range with lower emissivity over near-infrared range. Typically, the sample’s Si/B ratio of 1 : 1 shows highest integral intensity for about 0.85 compared with other molar ratios. It can be used as a more simple and effective method to obtain infrared ceramic SiB6 with high emissivity.