Statistical Approach for Optimization of Physiochemical Requirements on Alkaline Protease Production from Bacillus licheniformis NCIM 2042

The optimization of physiochemical parameters for alkaline protease production using Bacillus licheniformis NCIM 2042 were carried out by Plackett-Burman design and response surface methodology (RSM). The model was validated experimentally and the maximum protease production was found 315.28 U using optimum culture conditions. The protease was purified using ammonium sulphate (60%) precipitation technique. The HPLC analysis of dialyzed sample showed that the retention time is 1.84 min with 73.5% purity. This enzyme retained more than 92% of its initial activity after preincubation for 30 min at 37°C in the presence of 25% v/v DMSO, methanol, ethanol, ACN, 2-propanol, benzene, toluene, and hexane. In addition, partially purified enzyme showed remarkable stability for 60 min at room temperature, in the presence of anionic detergent (Tween-80 and Triton X-100), surfactant (SDS), bleaching agent (sodium perborate and hydrogen peroxide), and anti-redeposition agents (Na2CMC, Na2CO3). Purified enzyme containing 10% w/v PEG 4000 showed better thermal, surfactant, and local detergent stability

Ultrafast Green Single Photon Emission from an InGaN Quantum Dot-in-a-GaN Nanowire at Room Temperature

In recent years, there has been a growing demand for room-temperature visible single-photon emission from InGaN nanowire-quantum-dots (NWQDs) due to its potential in developing quantum computing, sensing, and communication technologies. Despite various approaches explored for growing InGaN quantum dots on top of nanowires (NWs), achieving the emission of a single photon at room temperature with sensible efficiency remains a challenge. This challenge is primarily attributed to difficulties in accomplishing the radial confinement limit and the inherent giant built-in potential of the NWQD. In this report, we have employed a novel Plasma Assisted Molecular Beam Epitaxy (PAMBE) growth approach to reduce the diameter of the QD to the excitonic Bohr radius of InGaN, thereby achieving strong lateral confinement. Additionally, we have successfully suppressed the strong built-in potential by reducing the QD diameter. Toward the end of the report, we have demonstrated single-photon emission (${\lambda}$ = 561 nm) at room-temperature from the NWQD and measured the second-order correlation function $g^{2}(0)$ as 0.11, which is notably low compared to other reported findings. Furthermore, the lifetime of carriers in the QD is determined to be 775 ps, inferring a high operational speed of the devices

Investigation of Magnesium Silicate as an Effective Gate Dielectric for AlGaN/GaN Metal Oxide High Electron Mobility Transistors (MOSHEMT)

In this study, a 6 nm layer of Magnesium Silicate (Mg-Silicate) was deposited on AlGaN/GaN heterostructure by sputtering of multiple stacks of MgO and SiO$_{2}$, followed by rapid thermal annealing in a nitrogen (N$_{2}$) environment. The X-ray photoelectron spectroscopy (XPS) analysis confirmed the stoichiometric Mg-Silicate (MgSiO$_{3}$) after being annealed at a temperature of 850 $^\circ$C for 70 seconds. Atomic force microscopy (AFM) was employed to measure the root mean square (RMS) roughness (2.20 nm) of the Mg-Silicate. A significant reduction in reverse leakage current, by a factor of three orders of magnitude, was noted for the Mg-Silicate/AlGaN/GaN metal-oxide-semiconductor (MOS) diode in comparison to the Schottky diode. The dielectric constant of Mg-Silicate($\mathcal{E}_{Mg-Silicate}$) and the interface density of states (D$_{it}$) with AlGaN were approximated at $\sim$ 6.6 and 2.0 $\times$ 10$^{13}$ cm$^{-2}$eV$^{-1}$ respectively, utilizing capacitance-voltage (CV) characteristics

Optimization of physicochemical parameters for phenol biodegradation by Candida tropicalis PHB5 using Taguchi Methodology

The Taguchi orthogonal array (OA) design of experiments methodology, a quality optimization tool, was used to improve the phenol biodegradation potential of the yeast Candida tropicalis PHB5. At three levels, an OA was selected to analyze the effects of the different physicochemical process factors. Experiments were undertaken to confirm the effectiveness of this method and the main factors affecting the growth of C. tropicalis on phenol and its subsequent degradation were found, together with the optimal factor levels. Predicted results showed that biomass yield could be increased from 1,051.96 to 2,495.74 mg/l and the subsequent amount of phenol degraded could be increased from 879.42 to 2,386.43 mg/l. Based on Taguchi methodology, an overall enhancement of growth by 137.24% and phenol degradation by 171.49% could be attained. Validation experiments showed that the growth and phenol biodegradation was significantly improved by up to 132.4% and 165.64%, respectively

Oxalato-bridged oligonuclear complexes of cadmium(II)/lead(II) with bipyridine coligands: Synthesis, crystal structure, electronic spectra, density functional theory calculation and effect of organic compounds on the fluorescence property

A trinuclear [Cd3(ox)2(bipy)5](ClO4)2 (1) and a dinuclear [Pb2(ox)(bipy)2(NO3)2(H2O)2] (2) oxalatobridged complex, where ox = oxalate dianion and bipy = 2,20-bipyridine, have been synthesized and characterized by elemental analysis, IR spectroscopy and X-ray crystallography. Structural determination for complex 1 reveals a cationic species of C2 symmetry having two Cd(bipy)2 fragments connected through bridging oxalate to a central Cd(bipy) unit. Complex 2 is a neutral centrosymmetric species having two Pb (bipy)(NO3)(H2O) units connecting through the bridging oxalate. The dinuclear fragments through Hbonding as well as p\u2013p interactions result in a 2D supramolecular network. Since complex 1 exhibits intense fluorescence (kex = 284 nm, kem = 315, 329 and 356 nm) in methanol at room temperature with a fluorescence quantum yield Us = 0.41, it was tested in association with several aromatic compounds. The results show a pronounced fluorescence quenching and enhancement in presence of nitrobenzene and m-toluidine, respectively. The outcome from DFT calculations is discussed and compared with the experimental electronic, IR spectral and X-ray structural data

Approaches towards the enhanced production of Rapamycin by Streptomyces hygroscopicus MTCC 4003 through mutagenesis and optimization of process parameters by Taguchi orthogonal array methodology

The present research was conducted to define the approaches for enhanced production of rapamycin (Rap) by Streptomyces hygroscopicus microbial type culture collection (MTCC) 4003. Both physical mutagenesis by ultraviolet ray (UV) and chemical mutagenesis by N-methyl-N-nitro-N-nitrosoguanidine (NTG) have been applied successfully for the improvement of Rap production. Enhancing Rap yield by novel sequential UV mutagenesis technique followed by fermentation gives a significant difference in getting economically scalable amount of this industrially important macrolide compound. Mutant obtained through NTG mutagenesis (NTG-30-27) was found to be superior to others as it initially produced 67% higher Rap than wild type. Statistical optimization of nutritional and physiochemical parameters was carried out to find out most influential factors responsible for enhanced Rap yield by NTG-30-27 which was performed using Taguchi orthogonal array approach. Around 72% enhanced production was achieved with nutritional factors at their assigned level at 23 °C, 120 rpm and pH 7.6. Results were analysed in triplicate basis where validation and purification was carried out using high performance liquid chromatography. Stability study and potency of extracted Rap was supported by turbidimetric assay taking Candida albicans MTCC 227 as test organism

Potential use of polyphenol oxidases (PPO) in the bioremediation of phenolic contaminants containing industrial wastewater

The present review emphasizes on the use of Polyphenol oxidase (PPO) enzyme in the bioremediation of phenolic contaminants from industrial wastewater. PPO is a group of enzyme that mainly exists in two forms; tyrosinase (E.C. 1.14.18.1) and laccase (E.C. 1.10.3.1) which are widely distributed among microorganisms, plants and animals. These oxidoreductive enzymes remain effective in a wide range of pH and temperature, particularly if they are immobilized on some carrier or matrices, and they can degrade a wide variety of mono and/or diphenolic compounds. However, high production costs inhibit the widespread use of these enzymes for remediation in industrial scale. Nevertheless, bench studies and field studies have shown enzymatic wastewater treatment to be feasible options for biodegradation of phenols through biological route. Nanomaterials-PPO conjugates have been also applied for removal of phenols which has successfully lower down the drawbacks of enzymatic water treatment. Therefore in this article various approaches and current state of use of PPO in the bioremediation of wastewater, as well as the benefits and disadvantages associated with the use of such enzymes have been overviewed

p-Toluate-bridged dinuclear Cu(II) complexes in combination with tridentate chelating ligand: Crystal structure, density functional theory calculation, DNA/protein binding and catecholase activity

The dinuclear Cu(II) complexes [Cu2(L1)2(mb)]⋅ClO4 (1) and [Cu2(L2)2(mb)]⋅ClO4 (2) (HL1 = 2-[(2-diethylaminoethylimino)methyl]phenol; HL2 = 2-[1-(2-diethylaminoethylimino)propyl]phenol; mb = 4-methylbenzoate) were synthesized and characterized using X-ray crystal structure analysis and spectroscopic methods. Complexes 1 and 2 are dinuclear with distorted square pyramidal Cu (II) geometries, where Schiff base coordinates with tridentate (N,N,O) chelating mode and mb bridges two metal centres. Optimized structures and photophysical properties of ligands and complexes were calculated using density functional theory and time-dependent density functional theory methods using B3LYP functional with 6-31G (d,p) and LanL2MB basis sets. Interactions of the complexes with bovine serum albumin (BSA) and human serum albumin (HSA) were studied using UV–visible absorption and fluorescence spectroscopies and the calculated values of association constants (M−1) are 1.7 × 105 (1–BSA), 5.7 × 105 (2–BSA), 1.6 × 105 (1–HSA) and 6.9 × 105 (2–HSA). Interactions of the complexes with calf thymus DNA were also investigated and the binding affinities are 1.4 × 105 and 1.6 × 105 M−1 for 1 and 2, respectively. Both complexes catalytically oxidize 3,5-di-tert-butylcatechol to 3,5-di-tert-butylbenzoquinone in the presence of molecular oxygen