Enhanced Production of Poly (γ-glutamic acid) from <Emphasis Type="Italic">Bacillus licheniformis</Emphasis> NCIM 2324 by Using Metabolic Precursors

The aim of the present work was to study the effect of addition of different amino acids and tricarboxylic acid cycle intermediates as metabolic precursors on the production of poly (γ-glutamic acid) (PGA) by Bacillus licheniformis NCIM 2324. A maximum yield of 35.75 g/l was obtained with the medium supplemented with 0.5 mM l-glutamine and 10 mM α-ketoglutaric acid as compared to 26.12 g/l PGA achieved with the control in the absence of metabolic precursors. Addition of precursors also enhanced the utilization of l-glutamic acid during fermentation.     

Green Luminescent CdTe Quantum Dot Based Fluorescence Nano-Sensor for Sensitive Detection of Arsenic (III)

Arsenic (As³⁺) is a hazardous and ubiquitous element; hence the quantitative detection of arsenic in various kinds of environmental sample is an important issue. Herein, we reported L-cysteine capped CdTe Quantum dot based optical sensor for the fluorometric detection of arsenic (III) in real water sample. The method is based on the fluorescence quenching of QDs with the addition of arsenic solution that caused the reduction in fluorescence intensity due to strong interaction between As³⁺ and L-cysteine to form As(Cys)₃. The calibration curve was linear over 2.0 nM-0.5 μM arsenic with limit of detection (LOD) of 2.0 nM, correlation coefficient (r²) of 0.9698, and relative standard deviation (RSD %) of 5.2%. The Stern-Volmer constant for the quenching of CdTe QDs with As³⁺ at optimized condition was evaluated to be 1.17 × 10⁸ L mol^?1 s^?1. The feasibility of the sensor has been analyzed by checking the inference of common metal ions available in the water such as K⁺, Na⁺, Mg²⁺, Ca²⁺, Ba²⁺, Cu²⁺, Ni²⁺, Zn²⁺, Al³⁺, Co²⁺, Cr²⁺, Fe³⁺ and its higher oxidation state As⁵⁺.

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Graphical Abstract Schematic representation of As³⁺ detection by L-Cysteine capped CdTe QDs

     

A new superconvergent collocation method for eigenvalue problems

Here we propose a new method based on projections for the approximate solution of eigenvalue problems. For an integral operator with a smooth kernel, using an interpolatory projection at Gauss points onto the space of (discontinuous) piecewise polynomials of degree , we show that the proposed method exhibits an error of the order of for eigenvalue approximation and of the order of for spectral subspace approximation. In the case of a simple eigenvalue, we show that by using an iteration technique, an eigenvector approximation of the order can be obtained. This improves upon the order for eigenvalue approximation in the collocation/iterated collocation method and the orders and for spectral subspace approximation in the collocation method and the iterated collocation method, respectively. We illustrate this improvement in the order of convergence by numerical examples.

     

Synthesis and Antibacterial Activity of Benzazolyl Azolyl Sulfamoyl Acetamides

A new class of benzazolyl azolyl sulfamoyl acetamides was prepared from azolyl sulfamoyl acetates and benzazolyl amines in the presence of KO^tBu in tetrahydrofuran. Compounds with benzothiazole‐thiazole, benzimidazole‐thiazole, benzothiazole‐imidazole, and benzimidazole‐imidazole moieties exhibited excellent antibacterial activity against Bacillus subtilis.     

Fermentative production of curdlan

Curdlan was produced by pure culture fermentation using Agrobacterium radiobacter NCIM 2443. Three different carbon sources (glucose, sucrose, maltose) were selected for study. Sucrose was found to be the most efficient. Utilization of sugar during the course of fermentation was studied, and the data were correlated to the production of curdlan. Curdlan mimics a secondary metabolite, in that its synthesis is associated with the poststationary growth phase of nitrogen-depleted batch culture. This was inferred from the results obtained from utilization of nitrogen. Regulation of pH at 6.1 +/- 0.3 resulted in an increased yield of curdlan from 2.48 to 4.8 g/L, and the corresponding increase in succinoglucan production was from 1.78 to 2.8 g/L. An attempt was made to increase curdlan production by the addition of the uridine nucleotides UMP and UDP-glucose to the fermentation broth. It was found that UDP-glucose at 0.8 microg/mL and UMP at 0.6 microg/mL served as precursors for curdlan and succinoglucan production when added after 18 h of nitrogen depletion in the fermentation broth.     

A bijection between certain non-crossing partitions and sequences

We present a bijection between non-crossing partitions of the set [2n+1] into n+1 blocks such that no block contains two consecutive integers, and the set of sequences such that 1?s_i?i, and if s_i=j, then s_i-r?j-r for 1?r?j-1.     

Isolation and Characterization of Acrylamidase from <Emphasis Type="Italic">Arthrobacter</Emphasis> sp. DBV1 and Its Ability to Biodegrade Acrylamide

Although acrylamide finds diverse industrial applications, its presence in the environment is hazardous due to its carcinogenic, neurotoxic, and teratogenic properties. In spite of the general toxicity of acrylamide in the monomer form, some microorganisms are able to use it as a source of energy by catabolizing it to ammonia and acrylic acid by means of acrylamidase (EC 3.5.1.4). The present work reports on a novel soil isolate as an acrylamide-degrading bacteria. Based on biochemical characterization and 16S ribosomal RNA (rRNA) gene sequence, the bacterial strain was identified as Gram-positive Arthrobacter sp. DBV1. The optimum growth conditions were found to be temperature (30 °C) and pH 6.0 to 7.0. Evaluation of the effect of concentration of acrylamide (10–50 mM) incorporated into minimal medium showed maximum growth of Arthrobacter sp. DBV1 at 30 mM acrylamide. The biodegradation of acrylamide was confirmed by HPLC analysis. Acrylamidase was isolated and characterized for temperature and pH optima, substrate specificity by using different amides, and the effect of different activators/inhibitors such as metal ions and amino acids. These finding suggests that the strain could be attractive for biodegradation of acrylamide from the environment and also possibly from foods containing preformed acrylamide.     

Dual-mode semisquaraine-based sensor for selective detection of Hg2+ in a micellar medium

[reaction: see text] A novel chemosensor based on semisquaraine dye (SSQ) for selective detection of Hg2+ is described. SSQ is obtained in quantitative yields from the reaction between squaric acid and 6-ethoxy-2-quinaldinium iodide. SSQ in combination with surfactant shows a dual chromogenic and fluorogenic response selectively toward Hg2+ as compared to Li+, Na+, K+, Ag+, Ca2+, Mg2+, Zn2+, Pb2+, Cd2+, Cu2+, and Fe3+ due to the soft acid nature and size of the mercuric ion.     

Effect of water on foaming properties of diglycerol fatty acid ester-oil systems

We have studied the effect of added water on the nonaqueous foaming properties of diglycerol fatty acid ester nonionic surfactant systems. Diglycerol monomyristate (designated as DGM) could not foam in nonpolar oils squalane and hexadecane at normal room temperature. Nevertheless, addition of a small amount of water induces a dramatic change in foaming properties. Both the foamability and foam stability increases with the amount of added water within the studied concentration range. Phase behavior study showed that in the dilute regions there is dispersion of solid surfactant in the aforementioned oils in the DGM systems. The particle size of the dispersed solid phase was found to be several tens of microns in the water free system, and hence it tends to coagulate and precipitate. In the case of shorter alkyl chain length, diglycerol monolaurate (DGL) surfactant-oil systems, dispersion of lamellar liquid crystal (Lalpha) is observed at room temperature, and the poor foaming properties were attributed to the large particle size of the liquid crystal. In both the DGL and DGM-oil systems, we observed a tendency of the particle size to decrease with the increasing concentration of added water. At higher temperature, the solid surfactant transforms to lamellar liquid crystal phase, and foaming is improved in the DGM/squalane system. Foams are stable for several minutes. Judging from the foaming test and particle size distribution data it can be concluded that the poor foaming in the diglycerol fatty acid esters-oil systems may possibly be due to bigger particle size, which causes precipitation. Addition of water results in the dispersion of smaller particles and improves the foaming behavior.     

Spectrofluorometric Determination of Mercury and Lead by Colloidal CdS Nanomaterial

Heavy metal ions such as Hg and Pb are hazardous due to very high toxicity, mobility, and ability to accumulate through the food chain or atmosphere in the environment system. Therefore, ultrasensitive determination of mercury and lead is important to provide an evaluation index of ions in aqueous environment. This paper describes the investigation of surface modified quantum dots (QDs) as a sensing receptor for Hg²⁺ and Pb²⁺ ion detection by optical approach. Water-soluble L-cysteine-capped CdS QDs have been synthesized in aqueous medium. These functionalized nanoparticles were used as a fluorescence sensor for Hg²⁺ and Pb²⁺ ions, involved in the fluorescence quenching. The effect of foreign ions on the intensity of CdS QDs showed a low interference response toward other metal ions except Cu²⁺ and Fe²⁺ ions. The limit of detection (LOD) of this system is found to be 1.0 and 3.0 nM for Hg²⁺ and Pb²⁺ ions, respectively.