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Ionic liquids (ILs) have remarkable properties and applications in many areas of science. Phosphonium ILs have become important because of their unique chemical and thermal stabilities. The present work is focused on the synthesis, characterisation, physicochemical properties, and microbial toxicity assessment of phosphonium ILs bearing seven different fatty acid anions. The structures of the synthesised ILs were confirmed by 1H and 13C nuclear magnetic resonance (NMR) and FTIR spectroscopy. Physicochemical properties such as density and viscosity of pure ILs were measured at temperatures ranging from 298.15 to 313.15 K. The experimental density decreased, whereas the viscosity increased with an increasing number of carbon atoms in the anion. The derived properties were also found to be anion dependent. The thermal decomposition temperature was investigated by TGA. Subsequently, the toxicity profile of the ILs was determined for selected Gram positive and Gram negative bacteria and some species of fungi in terms of minimum inhibitory concentrations (MIC). The results show that the antimicrobial activities of the ILs are strongly related to the structures of the ILs, where an increase in toxicity was observed with increasing alkyl group chain length of the fatty acid anion.

The inclusion complexes of tenofovir disoproxil fumarate (TDF) with p-sulfonato-calix[4]arene (SCX4) and p-sulfanatothiacalix[4]arene (TSCX4) macrocycles are characterized through an array of experiments including 1H NMR, NOESY, HPLC, HRMS, FT-IR and PXRD in conjunction with the density functional theory. An encapsulation of TDF within SCX4 and TSCX4 macrocycles conduce 1:1 complexes those prevail over 1:2 or 1:3 Stoichiometries which exhibis distinct structural features. A loss of crystallinity accompanying the complexation ascertains the inclusion of the guest within the macrocycle. A comparison of the measured 13C NMR spectra of the complexes with individual hosts ascertains the cone conformation of SCX4 in such complexes as in its free state. It has been demonstrated that the TDF guest penetrates deeply within the cavity of SCX4 facilitating the hydrogen bonding interactions between adenine protons and the hydroxyl as well as methylene protons of the macrocycle. The measured 1H NMR spectra thus reveal large upfield signals (δ 8.35, 8.48 ppm) for adenine protons of the SCX4 complex. On the other hand, the partial encapsulation of TDF in TSCX4 reflects in the deshielding of hydroxyl protons in the measured 1H NMR spectra. The characteristic C=N and SO stretching vibrations in the infrared spectra engender’frequency shifts’ in the opposite directions compared to the individual host or guest. A simple reverse phase high performance liquid chromatography method is presented. The adenine encapsulation further has been qualitatively correlated with MRSA activities.

In this study, a siderophore, pyoverdine (PVD), has been isolated from Pseudomonas sp. and used to develop a fluorescence quenching-based sensor for efficient detection of nitrotriazolone (NTO) in aqueous media, in contrast to other explosives such as research department explosive (RDX), picric acid, and trinitrotoulene (TNT). The siderophore PVD exhibited enhanced fluorescence quenching above 50% at 470 nm for a minimal concentration (38 nM) of NTO. The limit of detection estimated from interpolating the graph of fluorescence intensity (at 470 nm) versus NTO concentration is found to be 12 nM corresponding to 18% quenching. The time delay fluorescence spectroscopy of the PVD-NTO solution showed a negligible change of 0.09 ns between the minimum and maximum NTO concentrations. The in silico absorption at the emission peak of static fluorescence remains invariant upon the addition of NTO. The computational studies revealed the formation of inter- and intramolecular hydrogen-bonding interactions between the energetically stable complexes of PVD and NTO. Although the analysis of Stern-Volmer plots and computational studies imply that the quenching mechanism is a combination of both dynamic and static quenching, the latter is dominant over the earlier. The static quenching is attributed to ground-state complex formation, as supported by the computational analysis.

PEGylation is a reductive alkylation of a protein N-terminal/α-amine of protein with mPEG chain by reducing agent. To obtain quantitative and site-specific PEGylation, sodium cyanoborohydride is commonly used as a reducing agent. The reduction process of sodium cyanoborohydride produces highly poisonous hydrogen cyanide, which may render the final product toxic. Herein, we have studied various reducing agents such as dimethylamine borane, triethylamine borane, trimethylamine borane, pyridine borane, morpholine borane, 2-picoline borane, and 5-ethyl-2-methyl-pyridine borane were tested as alternatives to sodium cyanoborohydride for the PEGylation of L-asparaginase. The characterization of reacted pegaspargase was carried out by SDS-PAGE, Western blotting, SEC-HPLC, RP-HPLC, SEC-MALS, CD, enzyme activity, and cell proliferation assays using with lymphoblast cells and MTS/PMS as substrate. Pyridine borane was determined to be the best acceptable reducing agent for PEGylation in terms of purity and activity. As a result, instead of sodium cyanoborohydride, pyridine borane can be employed.

A fast, robust and green bioreactor for arsenic sequestration from contaminated water was designed. In the two-tier bioreactor, bacterial arsenite detoxification (1 mM) was carried out followed by precipitation of arsenate in 5 min. The precipitate could be used for supercapacitor applications. This bioreactor yielded arsenic free water, therefore, this method can be adopted for scale-up. The combination of hypertolerant bacteria and fast precipitation indicates the robustness of this pilot bioreactor.

Efficient and sustainable removal of phosphate ions from an aqueous solution is of great challenge. Herein we demonstrated a greener route for phosphate recovery through struvite formation by using bacterial siderophore. This method was efficient for removal of phosphate as low as 1.3 mM with 99% recovery efficiency. The siderophore produced by Pseudomonas taiwanensis R-12-2 act as template for the nucleation of struvite crystals and was found sustainable for recycling the phosphorous efficiently after twenty cycles. The formation of struvite crystals is driven by surrounding pH (9.0) and presence of Mg2+ and NH4+ ions along with PO43- and siderophore which was further validated by computational studies. The morphology of struvite was characterized by scanning electron microscopy, followed by elemental analysis. Furthermore, our results revealed that the siderophore plays an important role in struvite biomineralization. We have successfully demonstrated the phosphate sequestration by using industrial waste samples, as possible application for environmental sustainability and phosphate conservation. For the first time electrochemical super-capacitance performance of the struvite was studied. The specific capacitance value for the struvite was found to be 320 F g-1 at 1.87 A g-1 and retained 92 % capacitance after 250 cycles. The study revealed the potential implications of siderophore for the phosphate recycling and the new mechanism for biomineralization by sequestering into struvite.

Introduction The limited anti-infectious drugs and growing antibiotic resistance among pathogenic bacteria underscore the urgent need to explore novel antimicrobial agents, preferably from a natural source. Propolis is the potent natural antimicrobial agent, which produced by honeybees using various plant exudates. However, it has been minimally studied against multidrug-resistant (MDR) microorganisms. In the present study, the authors have investigated the antibacterial activity of ethanolic extracts of Indian melifera propolis (IMP) samples and combinations of their lead compounds against three human clinical isolates. Methods Three multidrug-resistant microorganisms (MDRMs) were isolated from a human pus sample, and their molecular identification was carried out by 16S rRNA sequencing. The antibacterial activity of the IMP extracts and different combinations of chrysin, galangin, and phenethyl caffeate was determined by minimum inhibitory concentrations (MIC) using the 96-well plate microdilution method. Results Amongst, 19 IMP studied samples, IMP-5, IMP-14, and IMP-16 samples had the most potent antimicrobial activity against three MDR isolates. These samples had antimicrobial efficacy in the order of IMP16 > IMP14 > IMP5. The combinations of chrysin, galangin, and phenethyl caffeate had the lowest MIC values than individual components and above potent IMP extracts. Conclusions Certain IMP samples and combinations of chrysin, galangin, and phenethyl caffeate could be the best natural therapeutic agents to control the pathogenicity of MDRMs.

Siderophore are iron-scavenging biomolecules secreted by a variety of microorganisms in the environment that promote plant growth. In this study, we have identified a hydroxamate type siderophore desferrioxamine E produced by an indigenous salt tolerant Pseudomonas stutzeri strain SGM-1 under iron deficient condition. This bacterial strain was previously isolated from the saline-sodic soil sample on the basis of its salt tolerance through media enrichment. This strain could withstand at increasing salt concentrations (up to 12% w/v NaCl) and tolerated stress of acid as well as alkalinity, even grew over wide temperature ranges. Under iron deficient condition this isolate produced siderophore which was determined qualitatively by universal Chrome Azurol-Sulphonate (CAS) assay and quantitatively by spectrophotometry from the broth supernatant, also, its chemical type was determined by various type detection tests. Identification by liquid chromatography and mass spectrometry showed the hydroxamate type siderophore was desferrioxamine E. The efficacy of the desferrioxamine E was assessed for increasing the iron content of wheat (Triticum aestivum) plant, validated through Microwave Plasma Atomic Emission Spectroscopy (MP-AES). It is suggested that this strain is a useful plant growth promoting bioinoculant for enhancing iron content under stressed conditions for sustainable agricultural practices.

The present study aimed to investigate chemical profile, antioxidant and antimicrobial activities of Indian Melifera propolis (IMP) samples collected from 13 different states. Chemical characterisation of ethanolic extracts of IMP (EEMP) samples was carried out by using HPLC and 1HNMR spectroscopy. The antioxidant activity of EEMP samples was measured by DPPH, ABTS, and FRAP assay. Moreover, the antimicrobial activity of each EEMP sample tested against bacteria and yeast using a 96 well plate microdilution method. All EEMP samples had remarkable antioxidant and antimicrobial activities. The antioxidant potential of EEMP samples found to have a moderate positive correlation with their total phenolics and flavonoids content. Majority of EEMP samples had a minimum inhibitory concentration (MIC) ≤1mg/mL against Staphylococcus aureus. Chemometric analysis of 1HNMR data indicated that brown, green, green-brown, red and red-brown coloured IMP samples were chemically distinct from each other, and showed two separate clusters for northern and southern states propolis samples. HPLC analysis confirmed phenethyl caffeate was most common and abundant compound in IMP samples among studied compounds. In conclusion, this study may be helpful for defining the quality of IMP as a raw material, and also in finished food and health care products.

Abiotic stress factors hugely affect the agricultural productivity worldwide out of which the most hazardous factor is soil salinization. Most of the crops species are susceptible to increased soil salinity; there is a great interest in developing new strategies to ameliorate salt stress as well as to make robust crop species. In this study we have selected saline sodic soil. The isolation of bacterial species was carried out on the basis of salt tolerance ability and having PGP traits by enrichment technique. Characterization and identification of isolate was done by 16 S rDNA and Gyrase-B. The isolate SGM-1 could grow at increasing salt concentrations up to 12% w/v NaCl with wide temperature and pH ranges. Pseudomonas stutzeri SGM-1 showed elongation of cells as a response to salt stress. The selected strain of Pseudomonas stutzeriSGM-1 exhibited diazotrophy by growing on nitrogen free media along with expression of other PGP traits as phosphate solubilization, auxin and siderophore production. The amelioration of the salt stress to the Cicer arietinum plant by isolate's bio-fertigation was observed up to 300 mM of NaCl. This study provides the basis for role of adaptation of soil microorganism to thrive the high stress environment. Also, the isolate exhibited indigenous salt and other abiotic stress tolerance along with potential PGP traits which indicates that it could promote plant growth by contributing to macro and micro essential nutrition in salt and other abiotic stresses.

Groundwater arsenic pollution causes millions of deaths worldwide. Long term natural and anthropogenic activities have increased arsenic levels in groundwater causing higher threats of arsenic exposure. Arsenic hyper-tolerant Firmicute Bacillus firmus L-148 was isolated from arsenic limiting Lonar lake soil, which tolerated more than 3 M arsenic and could oxidize 75 mM arsenite [As(III)] in 14 days. It oxidized As(III) in presence of heavy metals and had unusual pH optima at 9.2. B. firmus L-148 was studied at the biochemical, protein, genomic and transcript level for understanding its arsenic oxidizing machinery. The proteomic and transcript analysis exhibited the presence of ars and aio operon and supported the inducible nature of ars operon. Robust, hyper-tolerant, fast As(III) oxidizing, least nutrient requiring and multi-metal resistance qualities of the strain were used in microcosm studies for bioremediation. Artificial groundwater mimicking microcosm with 75 mM As(III) was developed. Modulation of carbon source, iron and multi metals affected growth and As(III) oxidation rate. The As(III) oxidation was recorded to be 77% in 15 days in presence of sodium acetate and Fe ions. This microcosm study can be explored for bioremediation of arsenic contaminated water and followed by precipitation using other methods.

This research describes systematic investigations on sensing of high explosives such as picric acid (PA), RDX, NTO, and trinitrotoluene (TNT) in aqueous medium via fluorescence quenching of quinine sulfate (QS). Although all the explosives exhibit fluorescence quenching of QS, highest response is observed for PA. Fluorescence quenching of [Formula: see text][Formula: see text]50% (in contrast to pristine QS) at [Formula: see text][Formula: see text]390 nm is observed for 10 nm (2.29 [Formula: see text]g of PA dissolved in 20 [Formula: see text]l of distilled water). The analysis of the Stern–Volmer (SV) plot implies dominance of static quenching mechanism in comparison to dynamic quenching mechanism. Furthermore, the effect of operational temperature on fluoresce quenching response for PA has been investigated, and values of enthalpy, entropy, and Gibbs free energy of interaction at various temperatures are estimated. The temperature-dependent studies reveal that fluorescence quenching is due to formation of strong hydrogen bonds, complemented by computational analysis.

The ZnO, ZnO-Eugenol complex (ZnO-EG) and Ag decorated ZnO-Eugenol complex composite (0.5, 1.0% Ag-ZnO-EG) materials were effectively prepared by mechanochemical process. The synthesized materials were fully characterized by TG-DTA, FTIR, XRD and SEM-EDS characterization techniques. The granular nanocrystallites of ZnO were found to be transformed into fine porous bricks like morphology in ZnO-EG complex and 0.5, 1.0% Ag-ZnO-EG composites. All the as synthesized materials were evaluated for their significant antibacterial activities in order to identify their MIC values and zone of inhibition studies against four different bacterial species viz. Bacillus subtilis, Staphylococcus aureus, Escherichia coli and Pseudomonas aeruginosa. The mode of bactericidal activity shown by highest active 1.0% Ag-ZnO-EG composite was investigated on the basis of SEM analysis of the treated cells. The dual mode of action of the studied material illustrated direct pore formation on the cell surface of Gram negative Escherichia coli species whereas in Gram positive Bacillus subtilis the agglomeration of the composite on bacterial surface was spotted. The Ag decoration in ZnO-EG complex was found to be crucial to exhibit significant bactericidal activity in Ag-ZnO-EG composites.

Nutrient availability in nature influenced the microbial ecology and behavior present in existing environment. In this study, we have focused on isolation of arsenic-oxidizing cultures from arsenic devoid environment and studied effect of carbon starvation on rate of arsenite oxidation. In spite of the absence of arsenic, a total of 40 heterotrophic, aerobic, arsenic-transforming bacterial strains representing 18 different genera were identified. Nineteen bacterial species were isolated from tannery effluent and twenty-one from tannery soil. A strong co-relation between the carbon starvation and arsenic oxidation potential of the isolates obtained from the said niche was observed. Interestingly, low carbon content enhanced the arsenic oxidation ability of the strains across different genera in Proteobacteria obtained. This represents the impact of physiological response of carbon metabolism under metal stress conditions. Enhanced arsenic-oxidizing ability of the strains was validated by the presence of aio gene and RT-PCR, where 0.5- to 26-fold up-regulation of arsenite oxidase gene in different genera was observed. The cultures isolated from tannery environment in this study show predominantly arsenic oxidation ability. This detoxification of arsenic in lack of carbon content can aid in effective in situ arsenic bioremediation.

Hexavalent chromium [Cr(VI)] and arsenite [As(III)] are the most toxic forms of chromium and arsenic respectively, and reduction of Cr(VI) to Cr(III) and oxidation of As(III) to As(V) has great environmental implications as they affect toxicity and mobility of these toxic species. Bacillus firmus strain TE7, resistant to chromium and arsenic was isolated from tannery effluent. The strain exhibited ability to reduce Cr(VI) and oxidize As(III). It reduced 100 mg L −1 Cr(VI) within 60 h in nutrient broth and oxidized 150 mg L −1 As(III) within 10 h in minimal medium. It also completely reduced 15 mg L −1 Cr(VI) and oxidized 50 mg L −1 of As(III) simultaneously in minimal medium. To the best of our knowledge, this is the first bacterial strain showing simultaneous reduction of Cr(VI) and oxidation of As(III) and is a potential candidate for bioremediation of environments contaminated with these toxic metal species.