A multiband patch antenna with embedded square split ring resonators in non-Homogeneous substrate

The authors have attempted to influence an embedded square split ring resonator (SSRR) response in a stacked non-homogeneous substrate to demonstrate a quad-band antenna. The purpose is to produce multiband operations of a microstrip patch antenna. The highlighted factor is the effect of embedding an SSRR and the differing relative permittivity of the substrate on the side length of the SSRR. The analysis shows that a non-homogeneous dual substrate patch produces multiple bands compared to a single substrate patch antenna without any parameter change. A dual substrate antenna fabricated using FR4 and Rogers RT/Duroid 5880 copper clad sheets with a dimension of 85.6x54x0.908 mm3 (0.314λ0x0.198λ0x0.003λ0). The antenna resonates at 1.1, 2.45, 3.65 and 5.25 GHz in the L-, S- and C-bands. It is possible to employ the patch antenna in WLAN (dual-band) and WiMAX applications and suitable for mobile broadcast service at 1.1 GHz. The authors compare the simulated and measured results of a prototype in the article. The maximum measured gain is 5.48 dBi at 1.1 GHz and 4.025 dBi at 3.65 GHz. The measured bandwidth is 60 MHz (1.2%) at 5.25 GHz.

Biochemical characterization of two chitinases from Bacillus cereus sensu lato B25 with antifungal activity against Fusarium verticillioides P03

Bacterial chitinases are a subject of intense scientific research due to their biotechnological applications, particularly their use as biological pesticides against phytopathogenic fungi as a green alternative to avoid the use of synthetic pesticides. Bacillus cereus sensu lato B25 is a rhizospheric bacterium that is a proven antagonist of Fusarium verticillioides, a major fungal pathogen of maize. This bacterium produces two chitinases that degrade the fungal cell wall and inhibit its growth. In this work, we used a heterologous expression system to purify both enzymes to investigate their biochemical traits in terms of Km, Vmax, optimal pH and temperature. ChiA and ChiB work as exochitinases, but ChiB exhibited a dual substrate activity and it is also an endochitinase. In this work, the direct addition of these chitinases inhibited fungal conidial germination and therefore they may play a major role in the antagonism against F. verticillioides.

Dual Substrate Specificity of the Rutinosidase from Aspergillus niger and the Role of Its Substrate Tunnel

Rutinosidases (α-l-rhamnopyranosyl-(1-6)-β-d-glucopyranosidases, EC 3.2.1.168, CAZy GH5) are diglycosidases that cleave the glycosidic bond between the disaccharide rutinose and the respective aglycone. Similar to many retaining glycosidases, rutinosidases can also transfer the rutinosyl moiety onto acceptors with a free –OH group (so-called transglycosylation). The recombinant rutinosidase from Aspergillus niger (AnRut) is selectively produced in Pichia pastoris. It can catalyze transglycosylation reactions as an unpurified preparation directly from cultivation. This enzyme exhibits catalytic activity towards two substrates; in addition to rutinosidase activity, it also exhibits β-d-glucopyranosidase activity. As a result, new compounds are formed by β-glucosylation or rutinosylation of acceptors such as alcohols or strong inorganic nucleophiles (NaN3). Transglycosylation products with aliphatic aglycones are resistant towards cleavage by rutinosidase, therefore, their side hydrolysis does not occur, allowing higher transglycosylation yields. Fourteen compounds were synthesized by glucosylation or rutinosylation of selected acceptors. The products were isolated and structurally characterized. Interactions between the transglycosylation products and the recombinant AnRut were analyzed by molecular modeling. We revealed the role of a substrate tunnel in the structure of AnRut, which explained the unusual catalytic properties of this glycosidase and its specific transglycosylation potential. AnRut is attractive for biosynthetic applications, especially for the use of inexpensive substrates (rutin and isoquercitrin).

Impact of Dual Substrate Limitation on Biodenitrification Modeling in Porous Media

In this work, we consider a model of the biodenitrification process taking place in a spatially-distributed bioreactor, and we take into account the limitation of the kinetics by both the carbon source and the oxidized nitrogen. This model concerns a single type of bacteria growing on nitrate, which splits into adherent bacteria or free bacteria in the liquid, taking all interactions into account. The system obtained consists of four diffusion-convection-reaction equations for which we show the existence and uniqueness of a global solution. The system is approximated by a standard finite element method that satisfies an optimal a priori error estimate. We compare the results obtained for three forms of the growth function: single substrate limiting, “multiplicative” form, and “minimum” form. We highlight the limitation of the ‘ single substrate limiting model”, where the dependency of the bacterial growth on the nitrate is neglected, and find that the “minimum” model gives numerical results closer to the experimental results.

Increased Selectivity for Butanol in Clostridium Pasteurianum Fermentations via Butyric Acid Addition or Dual Feedstock Strategy

Volatility of the petroleum market has renewed research into butanol as an alternate fuel. In order to increase the selectivity for butanol during glycerol fermentation with Clostridium pasteurianum, butyric acid can be added to the medium. In this manuscript, different methods of extracellular butyric acid addition are explored, as well as self-generation of butyric acid fermented from sugars in a co-substrate strategy. Molasses was used as an inexpensive sugar substrate, and the optimal molasses to glycerol ratio was found to allow the butyric acid to be taken back up into the cells and increase the productivity of butanol from all carbon sources. When butyric acid is added directly into the media, there was no significant difference between chemically pure butyric acid, or butyric acid rich supernatant from a separate fermentation. When low concentrations of butyric acid (1 or 2 g/L) are added to the initial media, an inhibitory effect is observed, with no influence on the butanol selectivity. However, when added later to the fermentation, over 1 g/L butyric acid is taken into the cells and increased the relative carbon yield from 0.449 to 0.519 mols carbon in product/mols carbon in substrate. An optimized dual substrate fermentation strategy in a pH-controlled reactor resulted in the relative carbon yield rising from 0.439 when grown on solely glycerol, to 0.480 mols C product/mols C substrate with the dual substrate strategy. An additional benefit is the utilization of a novel source of sugars to produce butanol from C. pasteurianum. The addition of butyric acid, regardless of how it is generated, under the proper conditions can allow for increased selectivity for butanol from all substrates.

A Novel Inhibition Modality for Phosphodiesterase 2A

Phosphodiesterase type 2A (PDE2A) has received considerable interest as a molecular target for treating central nervous system diseases that affect memory, learning, and cognition. In this paper, the authors present the discovery of small molecules that have a novel modality of PDE2A inhibition. PDE2A possesses GAF-A and GAF-B domains and is a dual-substrate enzyme capable of hydrolyzing both cGMP and cAMP, and activation occurs through cGMP binding to the GAF-B domain. Thus, positive feedback of the catalytic activity to hydrolyze cyclic nucleotides occurs in the presence of appropriate concentrations of cGMP, which binds to the GAF-B domain, resulting in a “brake” that attenuates downstream cyclic nucleotide signaling. Here, we studied the inhibitory effects of some previously reported PDE2A inhibitors, all of which showed impaired inhibitory effects at a lower concentration of cGMP (70 nM) than a concentration effective for the positive feedback (4 μM). This impairment depended on the presence of the GAF domains but was not attributed to binding of the inhibitors to these domains. Notably, we identified PDE2A inhibitors that did not exhibit this behavior; that is, the inhibitory effects of these inhibitors were as strong at the lower concentration of cGMP (70 nM) as they were at the higher concentration (4 μM). This suggests that such inhibitors are likely to be more effective than previously reported PDE2A inhibitors in tissues of patients with lower cGMP concentrations.